REVIEW | doi:10.20944/preprints202306.0166.v1
Subject: Biology And Life Sciences, Biophysics Keywords: Raman, IR, spectroscopy, phytochrome, tetrapyrrole, photoswitch
Online: 2 June 2023 (09:01:39 CEST)
Phytochromes are biological photoswitches that translate light into a physiological function. Spec-troscopic techniques are essential tools in molecular research on these photoreceptors. This review is directed to summarize how resonance Raman and IR spectroscopy contributed to the under-standing of structure, dynamics, and reaction mechanism of phytochromes, outlining the substan-tial experimental and theoretical challenges and describing the strategies to master them. It is shown that the potential of the various vibrational spectroscopic techniques can be most efficient-ly exploited in integral approaches by combination with theoretical methods as well as other ex-perimental techniques.
ARTICLE | doi:10.20944/preprints202308.1981.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: MoS2 dome; Raman excitation profile; biaxial strain
Online: 30 August 2023 (04:52:08 CEST)
This work describes a resonance Raman study performed in domes of monolayer MoS2 using 23 different laser excitation energies covering the visible and near-infrared (NIR) ranges. The multiple-excitation results allowed us to investigate the exciton-phonon interactions of different phonons (A1’, E’ and LA) with different electronic and excitonic optical transitions in biaxially strained monolayer MoS2. The analysis of the intensities of the two first-order peaks, A1’ and E’, and the double-resonance 2LA Raman band as a function of the laser excitation furnished the values of the energies of the indirect gap and the excitonic transitions in the strained MoS2 domes. It was noticed that the out-of-plane A1’ phonon mode is significantly enhanced only by the indirect gap I and the C exciton, whereas the in-plane E’ mode is only enhanced by the C exciton of MoS2 dome, revealing thus a weak interaction of these phonons with the A and B excitons in the strained MoS2 domes. On the other hand, the 2LA Raman band is significantly enhanced at the indirect gap I transition and by the A (or B) exciton, but not enhanced by the C exciton, showing thus that the LA edge-phonons that participate in the double resonance process in MoS2 have a weak interaction with the C exciton.
ARTICLE | doi:10.20944/preprints201809.0162.v1
Subject: Physical Sciences, Applied Physics Keywords: surface enhanced Raman spectroscopy; microfluidics; Klarite 312; chloroalkane; 1,2,3-trichloropropane
Online: 10 September 2018 (09:47:52 CEST)
Optofluidics, a research discipline combining optics with microfluidics, currently aspires to revolutionize the analysis of biological and chemical samples e.g. for medicine, pharmacology, or molecular biology. In order to detect low concentrations of analytes in water, we developed an optofluidic device containing a nanostructured substrate for surface enhanced Raman spectroscopy (SERS). The geometry of the gold surface allows localized plasmon oscillations to give rise to the SERS effect, in which the Raman spectral lines are intensified by the interaction of the plasmonic field with the electrons in the molecular bonds. The SERS substrate was enclosed in a microfluidic system, which allowed transport and precise mixing of the analyzed fluids, while preventing contamination or abrasion of the highly sensitive substrate. To illustrate its practical use, we employed the device for quantitative detection of persistent environmental pollutant 1,2,3-trichloropropane in water in submillimolar concentrations. The developed sensor allows fast and simple quantification of halogenated compounds and it will contribute towards the environmental monitoring and enzymology experiments with engineered haloalkane dehalogenase enzymes.
ARTICLE | doi:10.20944/preprints202107.0366.v1
Subject: Engineering, Automotive Engineering Keywords: bones; polarization-sensitive optical coherence tomography; Raman spectroscopy
Online: 16 July 2021 (09:25:51 CEST)
Aim of the presented research was to develop an optical sensing system to investigate the demineralization process of the bones. Optical measurement techniques are widely used and increasingly adapted in biological and biomedical applications due to their non-destructive nature and safety. Optical examination of the bone condition could facilitate clinical trials and improve the safety of patients. The authors used a set of complementary methods: polarization-sensitive optical coherence tomography (PS-OCT) and Raman spectroscopy. To stimulate the process of demineralization and gradual removal of the hydroxyapatite, the test samples of chicken bones were placed into 10% acetic acid. Measurements were carried out in two series. The first one took two weeks with data acquired every day. In the second series, the measurements were made during one day at an hourly interval (after 1, 2, 3, 5, 7, 10, and 24 hours). Raman spectroscopy was used to evaluate the disappearance of the hydroxyapatite. The relation between the content of hydroxyapatite and images recorded using OCT was analyzed and discussed. Moreover, the polarization properties of the bones have been evaluated. Based on OCT images, the retardation angles of the bones have been calculated. This work presents a preliminary study on the mechanism of bone demineralization and confirms the potential of the applied optical methods.
ARTICLE | doi:10.20944/preprints201804.0163.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Raman microspectroscopy; optical tweezers; optofluidics; E. coli; antibiotics
Online: 12 April 2018 (08:37:01 CEST)
Analyzing the cells in various body fluids can greatly deepen the understanding of the mechanisms governing the cellular physiology. Because of the variability of physiological and metabolic states, it is important to be able to perform such studies on individual cells. Therefore, we developed an optofluidic system in which we precisely manipulated and monitored individual cells of Escherichia coli. We used laser tweezers Raman spectroscopy (LTRS) in a microchamber chip to manipulate and analyze individual E. coli cells. We subjected the cells to antibiotic cefotaxime, and we observed the changes by the time-lapse microscopy and Raman spectroscopy. We found observable changes in the cellular morphology (cell elongation) and in Raman spectra, which were consistent with other recently published observations. We tested the capabilities of the optofluidic system and found it to be a reliable and versatile solution for this class of microbiological experiments.
ARTICLE | doi:10.20944/preprints202306.1626.v1
Subject: Medicine And Pharmacology, Pharmacy Keywords: Methicillin-resistant Staphylococcus aureus; biofilm; Antimicrobial agent; eugenol; Raman spectroscopy.
Online: 22 June 2023 (12:40:14 CEST)
Prevalence of antimicrobial-resistant bacteria has become a major challenge worldwide. Methicillin-resistant Staphylococcus aureus (MRSA)—a leading cause of infections—forms biofilms on polymeric medical devices and implants, increasing their resistance to antibiotics. Antibiotic administration before biofilm formation is crucial. Raman spectroscopy was used to assess MRSA biofilm development on solid culture media from 0 to 48 h. Biofilm formation was monitored by measuring DNA/RNA-associated Raman peaks and protein/lipid-associated peaks. The search for an antimicrobial agent against MRSA biofilm revealed that Eugenol was a promising candidate as it showed significant potential for breaking down the biofilm. Eugenol was applied at different times to test the optimal time for inhibiting MRSA biofilms, and the Raman spectrum showed that the first 5 h of biofilm formation was the most antibiotic-sensitive time. This study investigated the performance of Raman spectroscopy coupled with Principal Component Analysis (PCA) to identify planktonic bacteria from biofilm conglomerates. Raman analysis, microscopic observation, and quantification of the biofilm growth curve indicated early adhesion from 5 to 10 h of incubation time. Therefore, Raman spectroscopy can help in monitoring biofilm formation on a solid culture medium and performing rapid antibiofilm assessments with new antibiotics during the early stages of the procedure.
ARTICLE | doi:10.20944/preprints202311.0271.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: Metal_2D semiconductor interface; 2D semiconductor material; Raman and Photoluminescence Spectroscopy
Online: 9 November 2023 (02:36:21 CET)
Two-dimensional (2D) semiconductors like Transitional Metal Dichalcogenides (TMDCs) have attracted strong research interest in the last decade. Unlike the more celebrated 2D material graphene, TMDCs like molybdenum disulfide(MoS2) possess bandgap. The number of layers critically depends on the band structure of MoS2. For example, it is indirect for bulk MoS2. However, it becomes direct bandgap material for a monolayer MoS2. Monolayer MoS2, therefore, becomes an important material for photoelectronic devices. An essential aspect of such devices is the metal-semiconductor junction. Metal-TMDC junction is, therefore, a well-studied interface due to its importance for 2D materials-based photoelectronic devices. Most importantly, it can be flexible, stretchable to it’s length, and bent to a large angle. We used metals like Au and Al to interface with TMDs like MoS2. We used silicon and PDMS as substrates. So, we have to focus on investigating the relative properties of various TMDCs. We see change in band energy and vibrational modes via Photoluminiscence and Raman spectroscopy as shown in the article. However, certain aspects are yet to be explored, for example, how this interface behaves in the presence of strain.
ARTICLE | doi:10.20944/preprints202306.0130.v1
Subject: Medicine And Pharmacology, Pharmacy Keywords: levofloxacin; orally disintegrating tablet; crystalline form; low frequency Raman spectroscopy
Online: 2 June 2023 (04:37:48 CEST)
: We evaluated the pharmaceutical properties of levofloxacin (LV) in the form of an orally disintegrating tablet (LVODT) to find a new usefulness of low frequency (LF) Raman spectroscopy. LVODT contained dispersed granules with diameters in the order of several hundred micrometers, which were composed of the active pharmaceutical ingredient (API), as confirmed by infrared (IR) microspectroscopy. On the contrary, the API and inactive pharmaceutical ingredients (non-APIs) were homogeneously distributed in LV tablet (LVT) formulations. Microscopic IR spectroscopy and thermal analyses showed that LVODT and LVT contained the API in different crystalline forms or environment around the API each other. Furthermore, powder X-ray diffraction showed that LVT contained a hemihydrate of the API, while LVODT showed a partial transition to the monohydrate form. This result was confirmed by microscopic LF Raman spectroscopy. Moreover, this method confirmed the presence of thin layers coating the outer edges of the granules that contained the API. Spectra obtained from these thin layers indicated the presence of titanium dioxide, suggesting that the layers coexisted with a polymer that masks the bitterness of API. The microscopic LF Raman spectroscopy results in this study indicated new applications of this method in pharmaceutical science.
ARTICLE | doi:10.20944/preprints202304.0044.v2
Subject: Chemistry And Materials Science, Theoretical Chemistry Keywords: Dioxins; POPs; h-BNC; graphene; white graphene; SERS; Raman
Online: 5 April 2023 (12:12:24 CEST)
The ability of 2D hybrid structures formed by boron, nitrogen and carbon atoms (h-BNCs) as potential substrates for surface enhanced Raman spectroscopy (SERS) detection of dioxin-like pollutants is theoretically analyzed. The strong confinement and high tunability of the electromagnetic response of the carbon nanostructures embedded within the h-BNC sheets point out that these hybrid structures could be promising for applications in optical spectroscopies, such as SERS. In this work, two model dioxin-like pollutants, TCDD and TCDF, and a model h-BNC surface composed by a carbon nanodisk of ninety-six atoms surrounded by a string of borazine rings, BNC96, are employed for the simulation of the adsorption complexes and the static and pre-resonance Raman spectra of the adsorbed molecules. A large affinity of BNC96 by these pollutants is reflected on the large interaction energies obtained for the most stable stacking complexes, with dispersion being the most important contribution to their stability. The large vibrational coupling of some active modes of TCDF and, specially, of TCDD makes the Raman static spectra display a ‘pure’ chemical enhancement of one order of magnitude. On the other hand, due to the strong electromagnetic response of BNC96, confined within the carbon nanodisk, pre-resonance Raman spectra obtained for TCDD and TCDF display large enhancement factors of 108 and 107, respectively. Promisingly, laser excitation wavelengths frequently used in SERS experiments also provoke significant Raman enhancements, around 104, for the TCDD and TCDF signals. Both the strong confinement of the electromagnetic response within the carbon domains and the high modulation of the resonance wavelengths within the visible and/or UV ranges in h-BNCs should lead to a higher sensitivity than graphene and white graphene parent structures, solving one of the main disadvantages of using 2D substrates for SERS applications.
ARTICLE | doi:10.20944/preprints202304.1111.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: viruses; SARS-CoV-2; Raman spectroscopy; magnetic beads; sample preparation
Online: 28 April 2023 (04:46:10 CEST)
We introduce a magnetic bead-based sample preparation scheme for enabling a Raman spectroscopic differentiation of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) positive and negative samples. The beads were functionalized with the angiotensin-converting enzyme 2 (ACE2) receptor protein, which is used as recognition element to selectively enrich SARS-CoV-2 on the surface of the magnetic beads. Subsequent Raman measurements directly enable discriminating SARS-CoV-2 positive and negative samples. The proposed approach is applicable for other virus species, too, when the specific recognition element is exchanged. Series of Raman spectra were measured on three types of samples, namely SARS-CoV-2, Influenza A H1N1 virus and a negative control. For each sample type, eight independent replicates were considered. All spectra are dominated by the magnetic bead substrate and no obvious differences between sample types are apparent. In order to address the subtle differences in the spectra, we calculated different correlation coefficients, namely the Pearson coefficient and the Normalized Cross Correlation coefficient. By comparing the correlation with the negative control differentiating between SARS-CoV-2 and Influenza A virus is possible. This study provides a first step towards the detection and potential classification of different viruses with the use of conventional Raman spectroscopy.
ARTICLE | doi:10.20944/preprints201802.0173.v1
Subject: Engineering, Mining And Mineral Processing Keywords: flooded chalk; Raman spectroscopy; enhanced oil recovery; carbonates; calcite; magnesite
Online: 27 February 2018 (04:59:33 CET)
Understanding the chalk-fluid interactions and the associated mineralogical and mechanical alteration at sub-micron scale are major goals in Enhanced Oil Recovery. Mechanical strength, porosity, and permeability of chalk are linked to mineral dissolution that occurs during brine injections, and affect the reservoir potential. This paper presents a novel "single grain" methodology to recognize the varieties of carbonates in rocks and loose sediments: Raman spectroscopy is a non-destructive, quick, and user-friendly technique representing a powerful tool to identify minerals down to 1 µm. An innovative working technique for oil exploration is proposed, as the mineralogy of micron-sized crystals grown in two flooded chalk samples (Liége, Belgium) was successfully investigated by Raman spectroscopy. The drilled chalk cores were flooded with MgCl2 for c. 1.5 (Long Term Test) and 3 years (Ultra Long Term Test) under North Sea reservoir conditions (Long Term Test: 130°C, 1 PV/day, 9.3 MPa effective stress; Ultra Long Term Test: 130°C, varying between 1-3 PV/day, 10.4 MPa effective stress). Raman spectroscopy was able to identify the presence of recrystallized magnesite along the core of the Long Term Test up to 4 cm from the injection surface, down to the crystal size of 1-2 µm. In the Ultra Long Term Test core the growth of MgCO3 affected nearly the entire core (7 cm). In both samples, no dolomite or high-magnesium calcite secondary growth could be detected when analysing 557 and 90 Raman spectra on the Long and Ultra Long Term Test, respectively. This study can offer Raman spectroscopy as a breakthrough tool in petroleum exploration of unconventional reservoirs, due to its quickness, spatial resolution, and non-destructive acquisition of data. These characteristics would encourage its use coupled with electron microscopes and energy dispersive systems or even electron microprobe studies.
REVIEW | doi:10.20944/preprints202205.0189.v1
Subject: Medicine And Pharmacology, Pathology And Pathobiology Keywords: Raman Spectroscopy; Medical application; Disease screening and diagnosis; Machine learning analyses
Online: 13 May 2022 (10:17:00 CEST)
Raman Spectroscopy has long been anticipated to augment clinical decision making, such as classifying oncological samples. Unfortunately, the complexity of Raman data has thus far inhibited its routine use in clinical settings. Traditional machine learning models have been used to help exploit this information, but recent advances in deep learning have the potential to improve the field. However, there are a number of potential pitfalls with both traditional and deep learning models. We conduct a literature review to ascertain the recent machine learning methods used to classify cancers using Raman spectral data. We find that while deep learning models are popular, and ostensibly outperform traditional learning models, there are many methodological considerations which may be leading to an over-estimation of performance: primarily, small sample sizes which compound upon sub-optimal choices regarding sampling and validation strategies. Amongst several recommendations is a call to collate large benchmark Raman datasets, similar to those that have helped transform digital pathology, which researchers can use to develop and refine deep learning models.
ARTICLE | doi:10.20944/preprints202107.0033.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Raman intensity; anharmonicity; conformational isomerism; chain folding; jet cooling; rotational band contour; esters
Online: 1 July 2021 (14:22:39 CEST)
The conformational preferences of the ester group have the potential to facilitate the large amplitude folding of long alkyl chains in the gas phase. They are monitored by Raman spectroscopy in supersonic jet expansions for the model system methyl butanoate, after establishing a quantitative relationship to quantum-chemical predictions for methyl methanoate. This requires a careful analysis of experimental details, and a simulation of the rovibrational contours for near-symmetric top molecules. The technique is shown to be complementary to microwave spectroscopy in quantifying coexisting conformations. It confirms that a C-O-C(=O)-C-C chain segment can be collapsed into a single all-trans conformation by collisional cooling, whereas alkyl chain isomerism beyond this five-membered chain largely survives the jet expansion. This sets the stage for the investigation of linear alkyl alkanoates in terms of dispersion-induced stretched-chain to hairpin transitions by Raman spectroscopy.
ARTICLE | doi:10.20944/preprints201906.0095.v1
Subject: Physical Sciences, Optics And Photonics Keywords: paracetamol; laser-induced breakdown spectroscopy; cyanide; carbon Swan bands; principal component analysis; Raman spectroscopy; Fourier-Transform-infra-red spectroscopy
Online: 11 June 2019 (10:42:58 CEST)
Laser-induced breakdown spectroscopy (LIBS) of pharmaceutical drugs that contain paracetamol is investigated in air and argon atmospheres. Characteristic neutral and ionic spectral lines of various elements and molecular signatures of CN violet and C2 Swan band systems are observed. The relative hardness of all drug samples is measured as well. Principal component analysis, a multivariate method, is applied in data analysis for demarcation purposes of the drug samples. The CN violet and C2 Swan spectral radiances are investigated for evaluation of possible correlation of the chemical and molecular structures of the pharmaceuticals. Complementary Raman and Fourier-transform-infra-red spectroscopies are used record molecular spectra of the drug samples. The applicationof the above techniques for the drug screening are important for identification and mitigation of drugs that reveal additives that may cause adverse side-effects.
Subject: Chemistry And Materials Science, Biomaterials Keywords: hydroxylapatite, oxyhydroxylapatite, oxyapatite, tricalcium phosphate, tetracalcium phosphate, Raman spectroscopy, MAS-CP NMR spectroscopy, 2D-HETCOR NMR spectroscopy.
Online: 5 August 2021 (11:06:47 CEST)
Functional osseoconductive coatings based on hydroxylapatite (HAp) and applied preferentially by atmospheric plasma spraying to medical implant surfaces are a mainstay of modern implantology. During contact with the hot plasma jet, HAp particles melt incongruently and undergo complex dehydration and decomposition reactions that alter their phase composition and crystallographic symmetry, and thus, the physical and biological properties of the coatings. Surface analytical methods such as laser-Raman and nuclear magnetic resonance (NMR) spectroscopies are useful tools to assess the structural changes of HAp imposed by heat treatment during their flight along the hot plasma jet. In this contribution, the controversial information on the existence or non-existence of oxyapatite, i.e. fully dehydrated HAp as a thermodynamically stable compound is highlighted.
ARTICLE | doi:10.20944/preprints202311.0679.v1
Subject: Engineering, Mechanical Engineering Keywords: blood testing, biological information; hemoglobin; Raman spectroscopy; 3D Silicon micro-channel device
Online: 10 November 2023 (07:26:48 CET)
Blood testing is a crucial application in the field of clinical studies for disease diagnosis and screening, biomarkers discovery, organ function assessment, and personalized medication. Therefore, it is of utmost importance to collect precise data in a short time. In this study, we utilized Raman spectroscopy to analyze blood samples and extracted comprehensive biological information, including the primary components and compositions present in the blood. We conducted short-wavelength (532 nm green light) Raman scattering spectroscopy on blood samples, plasma, and serum, and subsequently analyzed the biological characteristics detected in each sample type. Our results indicated that whole blood had high hemoglobin content, which suggests that hemoglobin is a major component of blood. The characteristic Raman peaks of hemoglobin were observed at 690, 989, 1015, 1182, 1233, 1315, and 1562–1649 cm−1. Analysis of plasma and serum samples indicated the presence of β-carotene, which exhibited characteristic peaks at 1013, 1172, and 1526 cm−1. Additionally, in the field of medical blood testing, the novel 3D Silicon micro-channel device technology holds immense potential. It can serve as a substrate and helps to detect various diseases and biomarkers, providing real-time data to help medical professionals and patients better understand their health conditions. Changes in biological data collected in this manner could potentially be used to diagnose clinical diseases.
ARTICLE | doi:10.20944/preprints202309.0393.v2
Subject: Physical Sciences, Optics And Photonics Keywords: Laser-induced periodic surface structures (LIPSS); Surface-Enhanced Raman Spectroscopy (SERS); Femtosecond laser
Online: 12 September 2023 (08:34:34 CEST)
Laser-induced periodic surface structures (LIPSS) have gained significant attention due to their ability to modify the surface morphology of materials at the micro-nanoscale and show great promise for surface functionalization application. In this study, we specifically investigate the formation of LIPSS in silicon substrates and explore their impact on Surface-Enhanced Raman Spectroscopy (SERS) applications. This study reveals a stepwise progression of LIPSS formation in silicon, involving three distinct stages of LIPSS: 1) integrated Low-Spatial-Frequency LIPSS (LSFL) and High-Spatial-Frequency LIPSS (HSFL), 2) principally LSFL and 3) LSFL at the edge of the irradiated spot, elucidating the complex interplay between laser fluence, pulse number, and resulting surface morphology. Furthermore, from an application standpoint, these high-quality multi-scale periodic patterns lead to the next step of texturing the entire silicon surface with homogeneous LIPSS for SERS application. The potential of LIPSS-fabricated silicon substrates for enhancing SERS performance is investigated using thiophenol as a test molecule. The results indicate that the Au-coated combination of LSFL and HSFL substrate showcased the highest enhancement factor (EF) of 1.38 × 10^6. This pronounced enhancement is attributed to the synergistic effects of Localized Surface Plasmon Resonance (LSPR) and Surface Plasmon Polaritons (SPPs), intricately linked to HSFL and LSFL characteristics. These findings contribute to understanding LIPSS formation in silicon and their applications in surface functionalization and SERS, paving the way for sensing platforms.
ARTICLE | doi:10.20944/preprints202304.0894.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: excited state intramolecular proton transfer; structural dynamics; transient absorption; femtosecond fluorescence up-conversion; femtosecond stimulated Raman spectroscopy
Online: 25 April 2023 (07:10:11 CEST)
Bis-benzimidazole derivative (BBM) molecule, consisting of two 2-(2’-Hydroxyphenyl) benzim-idazole (HBI) halves, has been synthesized and successfully utilized as a ratiometric fluorescence sensor for the sensitive detection of Cu2+ based on enol-keto excited state intramolecular proton transfer (ESIPT). In this study, we strategically implement femtosecond stimulated Raman spec-troscopy and several time-resolved electronic spectroscopies, aided by quantum chemical calcula-tions to investigate the detailed primary photodynamics of BBM molecule. The results demonstrate that the ESIPT from BBM-enol* to BBM-keto* was observed in only one of HBI halves with a time constant of 300 fs, after that, the rotation of the dihedral angle between two HBI halves generate a planarized BBM-keto* isomer in 3 ps, leading to dynamics red shift of BBM-keto* emission.
ARTICLE | doi:10.20944/preprints201911.0079.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: environmental fate; Raman spectroscopy; chemometrics; principal component analysis, biodegradation; kinetics; post-processing; Whittaker filter; partial least square
Online: 8 November 2019 (03:03:34 CET)
Surfactants based on polyfluoroalky ethers are commonly used in fire-fighting foams on airport platforms, including for training sessions. Because of their persistence into the environment, their toxicity and their bioaccumulation, abnormal amounts can be found in ground and surface water following operations of airport platforms. As many other anthropogenic organic compounds, some concerns raised about their biodegradation. That is why the OECD 301 F protocol was implemented to appreciate the oxygen consumption during the biodegradation of a commercial fire-fighting foam. However, a Raman spectroscopic monitoring of the process was also attached to this experimental procedure to evaluate to what extent a polyfluoroalkyl ether disappeared from the environmental matrix. The relevance of our approach is to use chemometrics, including the Principal Component Analysis (PCA) and the Partial Least Square (PLS), in order to monitor the kinetics of the biodegradation reaction of one fire-fighting foam, Tridol S3B, containing a polyfluoroalkyl ether. This study provided a better appreciation of the partial biodegradation of some polyfluoroalkyl ethers by coupling Raman spectroscopy and chemometrics. This will ultimately facilitates the design of a future purification and remediation devices for the airport platforms.
ARTICLE | doi:10.20944/preprints202108.0530.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: graphene; electronic transport; Raman
Online: 27 August 2021 (17:03:07 CEST)
We report morpho-structural properties and charge conduction mechanisms of a foamy “graphene sponge”, having a density as low as ≈ 0.07 kg/m3 and a carbon to oxygen ratio C:O ≃ 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped millimetres-sized small flakes, containing small crystallites with a typical size of ≃ 16.3 nm. A defect density as high as ≃ 2.6×1011 cm−2 has been estimated by the Raman intensity of D and G peaks, dominating the spectrum from room temperature down to ≃ 153 K. Despite the high C:O ratio, the graphene sponge exhibits an insulating electrical behavior, with a raise of the resistance value at ≃ 6 K up to 5 orders of magnitude with respect to the room temperature value. A variable range hopping (VRH) conduction, with a strong 2D character, dominates the charge carriers transport, from 300 K down to 20 K. At T< 20 K, graphene sponge resistance tends to saturate, suggesting a temperature-independent quantum tunnelling. The 2D-VRH conduction originates from structural disorder and is consistent with hopping of charge carriers between sp2 defects in the plane, where sp3 clusters related to oxygen functional groups act as potential barriers.
ARTICLE | doi:10.20944/preprints202305.0053.v1
Subject: Engineering, Bioengineering Keywords: blood testing, biological information; hemoglobin; Raman spectroscopy; surface-enhanced Raman spectroscopy (SERS)
Online: 2 May 2023 (04:14:29 CEST)
Blood testing is a crucial medical application. In this study, we applied Raman spectroscopy to test blood samples and obtained complete biological information, including the main components and compositions in these samples. Short-wavelength (532-nm green light) Raman scattering spectroscopy was conducted on samples of normal blood, abnormal blood in 3 types of preparation including whole blood, plasma, and serum, and the underlying information reflected by the biological characteristics detected in each sample type were analyzed. Raman spectroscopy results indicated that normal blood had high hemoglobin content, which suggests that hemoglobin is a major component of blood. Hemoglobin affects blood oxygen level. The characteristic peaks of hemoglobin were observed at 690, 989, 1015, 1182, 1233, 1315, and 1562–1649 cm−1. Analysis of plasma and serum samples indicated the presence of β-carotene, which exhibited characteristic peaks at 1013, 1172, and 1526 cm−1. In addition, surface-enhanced Raman spectroscopy was used to collect biological signals that are difficult to obtain in conventional Raman spectroscopy, including those of small molecules such as hormones, antibodies, and enzymes. Changes in biological information collected in this manner can be used as a basis for potentially diagnosing clinical diseases.
ARTICLE | doi:10.20944/preprints202309.0034.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Raman Fiber Lasers; Ytterbium-doped Fiber Lasers; Stimulated Raman Scattering; Amplified Spontaneous emission
Online: 1 September 2023 (09:42:49 CEST)
This study explores into a comprehensive examination of an optical cavity system that integrates Raman and Yb-doped gain media, with a focus on understanding their interactions. The research implies a characterization of each gain medium within the cavity while subjecting them to diverse co-pumping conditions with the other. When the Raman-lasing cavity is co-pumped by exciting the Yb-doped section, the resulting composite laser exhibits significant threshold reductions and there is an optimal co-pumping regime that enhances energy transfer from pump to Stokes. As for the complementary cavity, where the Yb-doped gain is influenced by the co-pumped Raman gain, at moderate pump powers a light-controlling-light behavior phenomenon arises. Within this regime, the 1064-nm signal suppresses the Yb-generated 1115-nm signal, suggesting potential applications in intracavity optical modulation. For higher pump levels, a cooperative effect emerges whereby both lasers mutually enhance each other. Minor variations in the primary 974-nm pump power, even by just a few milliwatts, result in significant capabilities for switching or modulating the Stokes signal. Under these conditions of mutual enhancement, the hybrid optical system validates notable improvements regarding energy transfer efficiency and threshold reduction. This research provides valuable insights into the intricate dynamics of optical cavity systems and reveals promising avenues for applications in advanced optical modulation technologies.
ARTICLE | doi:10.20944/preprints202310.0520.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: chrysoberyl; Raman; trace elements; CIELab
Online: 10 October 2023 (03:19:18 CEST)
In this study, seventeen faceted gem-quality chrysoberyls exhibiting an attractive canary yellow color were investigated by a series of gemological, spectral, and chemical methods. Microscopic observation reveals distinct growth lines and inclusions, including CO2 fluids, carbon, and mineral crystals such as calcite, quartz, sillimanite, and mica, identified by the Raman spectrum. The FTIR spectrum exhibits the 2405 and 2160 cm-1 feature peaks and a 3223 cm-1 peak in all samples, which can be accompanied by the 3112 cm-1 shoulder, 3301, and 3412 and 3432 cm-1 peaks. The UV-Vis spectrum shows a Fe-related peak at 440 nm, along with the 650–660 nm band and the absorption band in the blue zone of the visible light. The chemical results of EDXRF reveal a V-poor, Cr-poor, and Fe-rich feature. The spectral and chemical results could contribute to explaining the origin of the canary yellow color, which originates from the abundant amount of Fe with very little influence from Cr or V.
ARTICLE | doi:10.20944/preprints202310.0112.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: NiO; domain walls; microwave; antiferromagnet; Raman
Online: 3 October 2023 (10:15:44 CEST)
Effective control of domain walls or magnetic textures in antiferromagnets promises to enable robust, fast, and non-volatile memories. The lack of net magnetic moment in antiferromagnets implies the need for creative ways to achieve such a manipulation. Here, we investigate changes in magnetic force microscopy (MFM) imaging and in magnon-related mode in Raman spectroscopy of virgin NiO films under a microwave pump. After the MFM and Raman studies, a combined action of broadband microwave (0.01-20 GHz, power scanned from −20 to 5 dBm) and magnetic field (up to 3 kOe) were applied to virgin epitaxial (111) NiO and (100) NiO films grown on (0001) Al2O3 and (100) MgO substrates, following which the MFM and Raman studies were repeated. We observed a suppression of the magnon-related Raman mode subsequent to the microwave exposure. Based on MFM imaging, this effect appears to be caused by the suppression of large antiferromagnetic domain walls due to the possible excitation of antiferromagnetic spin oscillations localized within the antiferromagnetic domain walls.
ARTICLE | doi:10.20944/preprints201901.0227.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: Microplastics, Nanoplastics, Optical Tweezers, Raman Spectroscopy
Online: 22 January 2019 (18:00:37 CET)
Our understanding of the fate and distribution of micro- and nano- plastics in the marine environment and their impact on the biota compartment is limited by the intrinsic difficulties of conventional analytical techniques (light scattering, FT-IR, Raman, optical and electron microscopies) in the detection, quantification and chemical identification of small particles in liquid samples. Here we propose the use of optical tweezers, a technique awarded in 2018 with the Nobel prize, as an analytical tool for the study of micro- and nano- plastics in sea water. In particular, we exploit the combination of optical tweezers with Raman spectroscopy (Raman Tweezers, RTs) to optically trap plastic particles with sizes from tens of µm down to 90 nm and unambiguously reveal their chemical composition. RTs applications are shown on particles made of the most common plastic pollutants, including polyethylene, polypropylene, nylon and polystyrene, that are artificially fragmented and aged directly in seawater. RTs allow us to assess the size and shapes of microparticles (beads, fragments, fibers) and can be applied to investigate particles covered with organic layers. Furthermore, operating at the single particle level, RTs enable unambiguous distinction of plastic particles from marine microorganisms and seawater minerals, overcoming the capacities of standard Raman spectroscopy in liquid, limited to average measurements. Coupled to suitable extraction and concentration protocols, RTs could have a strong impact in the study of the fate of micro and nanoplastics in marine environment, as well as in the understanding of the fragmentation processes on a multi-scale level.
ARTICLE | doi:10.20944/preprints202309.0176.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: water vapour; micro-pulse laser; Raman lidar
Online: 5 September 2023 (02:45:44 CEST)
It was for long time believed that lidar systems based on the use of high-repetition micro-pulse lasers could be effectively used to only stimulate atmospheric elastic backscatter echoes, and thus only exploited in elastic backscatter lidar systems. Their application to stimulate rotational and roto-vibrational Raman echoes, and consequently their exploitation in atmospheric thermodynamic profiling, was considered not feasible based on the technical specifications possessed by these laser sources until a few years ago. However, recent technological advances in the design and development of micro-pulse lasers, presently achieving high UV average powers (1-5 W) and small divergences (0.3-0.5 mrad), in combination with the use of large aperture telescopes (0.3-0.4 m diameter primary mirrors), allow to presently develop micro-pulse laser-based Raman lidars capable to measure the vertical profiles of atmospheric thermodynamic parameters, namely water vapour and temperature, both in daytime and nighttime. This paper is aimed at demonstrating the feasibility of these measurements and at illustrating and discussing the high achievable performance level, with a specific focus on water vapour profile measurements. The technical solutions identified in the design of the lidar system and their technological implementation within the experimental setup of the lidar prototype are also carefully illustrated and discussed.
ARTICLE | doi:10.20944/preprints202308.1898.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: 4B2MBN; FT-IR; FT-Raman; Photoluminescence; Antibacterial
Online: 29 August 2023 (03:43:33 CEST)
By slowly evaporating 4-bromo-2-methylbenzonitrile at room temperature, it was possible to make a single organic nonlinear optical crystal. The grown crystal's crystalline nature was verified, and the unit cell characteristics are provided as a = 4.08Å, b = 6.61 Å, c = 28.93Å, α = 90º, β = 90º, γ = 90º. The functional groups of the crystal produced were identified using the FTIR and FT-Raman spectra. The UV cutoff wavelength is found at 221.6 nm, and the transparency nature of the crystal was analyzed in the optical studies. The band gap of the grown crystal was estimated using the Taucs’ plot. The violet and red emissions of photoluminescence are discussed. A high dielectric constant was received at a low frequency. The TG/DTA curve shows that the grown crystal was stable up to 125.59 ºC. The Kurtz-Perry powder technique was applied to confirm the Second Harmonic Generation's (SHG) nature. By using the agar diffusion method, the antibacterial property of the grown 4B2MBN crystal was determined.
ARTICLE | doi:10.20944/preprints201612.0039.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: Cryogenic treatment; wear resistance; Raman intensity rate
Online: 7 December 2016 (11:13:10 CET)
This study explored the effects of cryogenic treatment on the microstructure, hardness, and wear-resistance of diamond-like carbon (DLC) by cryogenically treating NAK 80 mold steel coated with DLC. Raman spectroscopy analyzed the structure of the DLC film. Nanoindenter analyzed the hardness and Young’s modulus of the film, and their relationship determined the wear resistance. Wear test assessed the wear rate and friction coefficient of the DLC film. The results showed that cryogenic treatment increased the rate of carbide precipitation and refined the grain structure. Raman spectroscopy indicated that the Raman intensity rate (ID/IG) of treated DLC films was smaller than those without cryogenic treatment. When the sp3 bond increased, the hardness and wear-resistance of the DLC film also increased.
ARTICLE | doi:10.20944/preprints202310.1607.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: Raman spectroscopy; biosensing; exosomes; hybrid nanoparticles; zinc oxide
Online: 25 October 2023 (09:59:58 CEST)
Developing a biomolecular detection method that minimizes photodamage while maintaining an environment suitable for biological constituents to maintain their physiological state is expected to drive new diagnostic and mechanistic breakthroughs. In addition, ultra-sensitive diagnostic platforms are needed for rapid and point-of-care technologies for various diseases. Considering this, surface-enhanced Raman scattering (SERS) is proposed as a non-destructive and sensitive approach to address the limitations of fluorescence, electrochemical, and other optical detection techniques. However, to advance the applications of SERS, novel approaches to enhance the signal of substrate materials are needed to improve reproducibility and costs associated with manu-facture and scale-up. Due to their physical properties and synthesis, semiconductor-based nanostructures have gained increasing recognition as SERS substrates; however, low signal en-hancements have offset their widespread adoption. To address this limitation and assess the po-tential for use in biological applications, zinc oxide (ZnO) was coated with different concentra-tions (0.01-0.1 M) of gold (Au) precursor. When crystal violet (CV) was used as a model target with the synthesized substrates, the highest enhancement was obtained with ZnO coated with 0.05 M Au precursor. This substrate was subsequently applied to differentiate exosomes derived from three cell types to provide insight into their molecular diversity. We anticipate this work will serve as a platform for colloidal hybrid SERS substrates in future bio-sensing applications.
ARTICLE | doi:10.20944/preprints202309.1908.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: ruby; sapphire; low-temperature heating; diaspore; goethite; Raman
Online: 27 September 2023 (15:11:57 CEST)
A Gem-quality rubies and sapphires are often commercially heat treated at about 800°C or higher temperatures to enhance their colour and clarity, and hence quality. For this study, selected corundum samples containing diaspore- and goethite inclusions were heated step-by-step to a maximum of 1000 °C with the aim to monitor the dehydration and phase transformation of these oxyhydroxides to corundum and hematite during heating. Based on our experiments and in agreement with literature, the dehydration of diaspore in corundum occurs between 525 to 550 °C, whereas goethite transforms to hematite already between 300 and 325 °C. As both, diaspore and goethite are common inclusions in rubies, sapphires, and other corundum varieties, these dehydration reactions and phase transformations can be considered important criteria to separate unheated stones from heated ones, specifically in cases in which other methods (e.g. microscopy, FTIR) are unsuccessful.
ARTICLE | doi:10.20944/preprints202309.1379.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: Carbonate Minerals; calcite; aragonite, magnesite; dolomite; Raman spectroscopy
Online: 20 September 2023 (13:42:52 CEST)
This work presents a new discussion about the vibrational properties of the carbonate ion displayed in several different environments, not only the microparameters introduced by cation substitution and different crystal lattices but also the crystal aggregation, showing how their active Raman modes are affected by these changes by using data obtained with four different laser excitation sources. New Raman spectra excited at 1064 nm are reported for calcite, aragonite, and dolomite groups, also including magnesite, witherite, rhodochrosite, siderite, malachite and azurite. These new data contribute to the discussion and understanding of these materials and their spectra, bringing new observations based on the Raman modes, focusing on the internal symmetrical and asymmetrical stretching and bending modes of the carbonate ion, highlighting the differences observed in the relative intensity and width of the bands. The results indicate some evidence of the influence of the crystal habit and/or the growth of the mineral itself in the Raman spectrum. In addition, the data show the influence of the cation substitution upon the Raman band width and that small cations contribute to less rigid crystalline structures and, consequently, larger Raman bandwidths.
ARTICLE | doi:10.20944/preprints202309.1395.v1
Subject: Physical Sciences, Applied Physics Keywords: Remote Raman; Time-Gated; Traces Detection and Identification.
Online: 20 September 2023 (11:19:27 CEST)
Raman spectroscopy is a type of inelastic scattering that provides rich information about a sub-stance based on the coupling of the energy levels of their vibrational and rotational modes with incident light. It has been applied extensively in many fields. As there is an increasing need for remote detection of chemicals in planetary exploration and anti-terrorism, it is urgent to develop a compact and easily transportable fully automated remote Raman detection system for trace detection and identification of information with high-level confidence about the target’s compo-sition and conformation in real-time and for real field scenarios. Here, we present an unmanned vehicle-based remote Raman system, which includes a 266 nm air-cooling passive Q-switched nanosecond pulsed laser of high-repetition frequency, a gated ICMOS, and an unmanned vehicle. This system obtains good spectral signals from remote distances ranging from 3 m to 10 m for simulating realistic scenarios, such as aluminum plate, woodblock, paperboard, black cloth, and leaves, and even for detected amounts as low as 0.1 mg. Furthermore, a CNN-based algorithm is implemented and packaged into the recognition software to achieve fast and more accurate de-tection and identification. This prototype provides a proof-of-concept for an unmanned vehicle with accurate remote substance detection in real-time, which can be helpful for remote detection and identification of hazardous gas, explosives, their precursors, and so forth.
ARTICLE | doi:10.20944/preprints202307.1315.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: amorphous carbon; particle accelerators; SEY; XPS; Raman spectroscopy
Online: 19 July 2023 (09:54:49 CEST)
The interest on amorphous carbon thin films with low secondary electron yield (SEY) has been increasing in the last years, to mitigate electron multipacting in particle accelerators and in RF devices. Previous works found that the SEY increases with the hydrogen amount and correlates with the Tauc gap. In this work, we analyse films produced by magnetron sputtering with different contents of hydrogen and deuterium, incorporated via target poisoning and sputtering of CxDy molecules. XPS was implemented to estimate the phase composition of the films. The maximal SEY was found to decrease linearly with the fraction of the graphitic phase in the films. These results are supported by Raman scattering and UPS. The graphitic phase decreases almost linearly for hydrogen and deuterium concentrations between 12% and 46% (at.), but abruptly decreases when the concentration reaches 53%. This vanishing of the graphitic phase is accompanied by a strong increase of SEY and of the Tauc gap. These results suggest that the SEY is not dictated directly by the concentration of H/D but by the fraction of graphitic phase. The results are supported by a model used to calculate SEY of films consisting of a mixture of graphitic and polymeric phases.
COMMUNICATION | doi:10.20944/preprints202104.0119.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: MoS2; photodetector; Raman; drop casting; infrared; thin film
Online: 5 April 2021 (12:21:57 CEST)
In this work, a highly efficient, molybdenum disulfide (MoS2) based near infrared (NIR) heterojunction photodetector is fabricated on a Si substrate using a cost-effective and simple drop casting method. A non-stoichiometric and inhomogeneous MoS2 layer with a S/Mo ratio of 2.02 is detected using energy dispersive X-ray spectroscopy and field emission scanning electron microscope analysis. Raman shifts are noticed at 382.42 cm-1 and 407.97 cm-1, validating MoS2 thin film growth with a direct bandgap of 2.01 eV. The fabricated n-MoS2/p-Si photodetector is illuminated with a 785 nm laser at different intensities, and demonstrate the ability of the photodetector to work in both regions, the forward biased and reverse biased from above 1.5 V and less than -1.0 V. The highest responsivity, R is calculated to be 0.52 A/W while the detectivity D* is 4.08 x 10^10 Jones for an incident light intensity of 9.57 mW/cm2. The minimum rise and fall times are calculated as 1.77 ms and 1.31 ms for an incident laser power of 9.57 mW/cm^2 and 6.99 mW/cm^2 respectively at a direct current bias voltage of 10 V. The demonstrated results are promising for the low-cost fabrication of a thin MoS2 film for photonics and optoelectronic device applications.
ARTICLE | doi:10.20944/preprints201905.0224.v1
Subject: Physical Sciences, Optics And Photonics Keywords: cylindrical vector beam, stimulated Raman scatting, Stokes shift.
Online: 17 May 2019 (11:11:32 CEST)
We present the generation and nonlinear frequency conversion of nanosecond cylindrical vector beams (CVBs) in two-mode fiber (TMF). Based on the polarized dependence vector mode coupling characteristic and the precise wavelength tunability of an acoustically-induced fiber grating (AIFG), the nanosecond cylindrical vector beams (CVBs, 1064 nm, 10 ns) is directly generated in a TMF with convenient switching characteristics between the radial and azimuthal vector beams. Furthermore, the stimulated Raman scattering (SRS) is produced based on the transmission of the nanosecond CVBs in the 100-meters long TMF, and the spatial intensity and polarization distributions characteristics the 1st-order Stokes shifted component is consistent with the nanosecond CVBs pump pulse. This work provides a method for achieving wavelength conversion of the CVBs in optical fiber.
ARTICLE | doi:10.20944/preprints202301.0536.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: graphene oxide; nanosheet; polyurethane; composite; XPS spectra; Raman spectra
Online: 30 January 2023 (02:43:12 CET)
Mechanically strong and thermally stable films obtained from a water-based polyurethane (PU) dispersion with small (0.1–1.5 wt.%) additions of graphene oxide nanosheet (GO) were studied through elemental analysis, X-ray photoelectron spectroscopy, differential thermogravimetry, and Raman spectroscopy. Moreover, the depletion of near-surface layers in nitrogen was presented for all the samples under study. It was found that the introduction of GO into a PU matrix was ac-companied by a partial reduction of graphene oxide nanosheet and an increase in the concentra-tion of defects in its structure.
ARTICLE | doi:10.20944/preprints202101.0154.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: Garnierite, Phase transformation, TGA/DSC, XRD, micro Raman spectroscopy
Online: 8 January 2021 (12:59:34 CET)
This study deals with vibrational and crystallographic aspects of the thermally induced transformation of serpentine-like garnierite into quartz, forsterite, and enstatite occurring at about 620 °C. Powder specimens of garnierite have been annealed in static air between room temperature and 1000 °C. The resulting products from the transformations detected based on thermogravimetric and differential thermal analysis, have been extensively characterized via microRaman spectroscopy, and X-ray diffraction. Our study shows that serpentine-like garnierite consists of a mixture of different mineral species. Furthermore, these garnierites and their composition can provide details based on the mineralogy and the crystalline phases resulting from the thermal treatment.
ARTICLE | doi:10.20944/preprints202007.0442.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: Carbonaceous material; Raman spectra; gold deposit; Hainan; Organic matter
Online: 19 July 2020 (20:52:43 CEST)
Carbonaceous material (CM) is common in meta-sediments and is generally interpreted to be intimately associated with gold mineralization. For the Bumo deposit in Hainan Province, South China, CM is mainly hosted by greenschist facies- to amphibolite-facies metamophic rocks of the Paleo- to Mesoproterozoic Baoban Group and by auriferous veins and is used as an important gold prospecting indicator. However, the genesis of CM and the relationship with gold mineralization are still not clear. Field work and thin section observation indicates that two types of CM occur, i.e., layered and veinlet. Layered CM, up to meters thick, prevails in the deposit. More importantly, Au-bearing sulfides are commonly distributed along the boundary between the quartz veins and layered CM. In contrast, veinlet CM, co-precipitated with gold and sulfides, has the thickness of micro- to centi- meters, and these thin veins occur in quartz veins and hydrothermally altered rocks. Scanning Electron Microscope (SEM) analysis indicates that layered CM has a stringy shape and laminate structure, while veinlet CM occurs as isometric particles. Raman carbonaceous material geothermometer indicates that layered CM with high maturity is formed at elevated temperatures of 400 – 550°C, consistent with X-ray diffraction (XRD) analysis. In contrast, veinlet CM with low maturity is formed at 200 – 350°C, generally consistent with gold mineralization. In addition, layered CM has δ13C values ranging from -30 to -20%, demonstrating a biogenic origin. Consequently, it is interpreted that layered CM is formed by a pre-ore metamorphic event during Caledonian, and its reducing nature promotes gold precipitation via destabilization of aqueous Au bisulfide complexes or facilitating sulfidation. Veinlet CM is hydrothermal origin, and its precipitation modified the chemical conditions of ore fluids, leading to the destabilization of Au complexes and thus favorable for mineralization.
ARTICLE | doi:10.20944/preprints202001.0322.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Tengchongite; microscopic laser Raman spectroscopy; infrared spectroscopy; Yunnan Province
Online: 27 January 2020 (07:53:31 CET)
Tengchongite is a uranyl molybdate uranium mineral and it was found and named by Chen 1985.No more scholars studied on tengchongite after Chen’s work, The identification of this mineral has only been confirmed by single crystal X-ray diffraction. In the paper, micro laser Raman spectroscopy and infrared spectroscopy are used to identify the spectroscopy properties of tengchongite. The studies fill in the gaps of more than 30 years in terms of the molecular spectroscopy research of tengchongite. The mineral has an ideal model of Ca(UO2)6(MoO4)2O5•12H2O its bands attributed to the vibrating units are clearly identified in the Raman spectrum. Symmetric stretching modes at 812 cm-1 and 839 cm-1 are assigned to ν1 (UO2)2+ ,The ν3 antisymmetric stretching modes of (UO2)2+ are observed at 896 cm-1, Symmetric stretching modes at 419-1 and 440 cm-1 are assigned to ν2 (UO2)2+ .Symmetric stretching modes at 919cm-1 are assigned to ν1(MoO4)2-,The ν3 antisymmetric stretching modes of (MoO4)2- are observed at 752 cm-1, the in-plane ν2(MoO4)2-and the out-of-plane ν4(MoO4)2- bending modes are at 169 cm-1 and 254 cm-1. IR spectrum of tengchongite shows the major uranyl band at 858 cm-1 and 693 cm-1, Mo-O bonds are observed at about 985 cm-1 and 780 cm-1, and H2O groups are present with a wide range peaks from 3100 cm-1 to 3500 cm-1 and 1647 cm-1, and the band at 1432.4 cm-1 is probably due to the stretching vibration hydroxyl (OH-1), therefore, tengchongite contains may include hydroxyl and its chemical formula needs to be modified .
ARTICLE | doi:10.20944/preprints201806.0097.v1
Subject: Chemistry And Materials Science, Other Keywords: collective vibration; raman spectroscopy; superconductivity; CuO2 plane; YBCO system
Online: 6 June 2018 (13:11:24 CEST)
The phonon modes in YBa2Cu3O7-δ and YBa2-xLaxCu3O7-δ systems have been systematically studied by Raman spectroscopy. The new phonon modes of 104 cm-1, 94 cm-1, and 89 cm-1 were found in all these samples. A crude estimate about the wavenumber of the collective vibration of the stable CuO2 plane was given in this paper. The standard deviations of the new phonons in YBa2Cu3O7-δ and YBa2-xLaxCu3O7-δ systems were discussed. The results of the calculation indicated that the 104 cm-1 mode probably stands the c-direction collective vibration of the stable CuO2 plane, the 94 cm-1 mode stands the a-direction vibration, and the 89 cm-1 mode stands b-direction vibration. The relevance between these phonons and the superconductivity was discussed. It is found that, as the Tc decreased, the 104 cm-1 mode and the 94 cm-1 mode softened, and the 89 cm-1 mode hardened slightly.
ARTICLE | doi:10.20944/preprints201805.0212.v1
Subject: Chemistry And Materials Science, Polymers And Plastics Keywords: polymer electrolyte; single-ion conducting; ionic conductivity; Raman spectroscopy
Online: 15 May 2018 (08:45:58 CEST)
Solvent-free, single-ion conducting electrolytes are sought after for use in electrochemical energy storage devices. Here, we investigate the ionic conductivity and how this property is influenced by segmental mobility and conducting ion number in crosslinked single-ion conducting polyether-based electrolytes with varying tethered anion and counter-cation types. Crosslinked electrolytes are prepared by the polymerization of poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) methyl ether acrylate, and ionic monomers. The ionic conductivity of the electrolytes is measured and interpreted in the context of differential scanning calorimetry and Raman spectroscopy measurements. A lithiated crosslinked electrolyte prepared with PEG31DA and STFSI monomers is found to have a lithium ion conductivity of 3.2 × 10-6 and 1.8 × 10−5 S/cm at 55 and 100 °C, respectively. The percentage of unpaired anions for this electrolyte was estimated at about 23% via Raman spectroscopy. Despite the large variances in metal cation – STFSI binding energies as predicted via DFT and large variations in ionic conductivity, STFSI-based crosslinked electrolytes with the same charge density and varying cations (Li, Na, K, Mg, and Ca) were estimated to all have unpaired anion populations in the range of 19 to 29%.
ARTICLE | doi:10.20944/preprints201705.0110.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: surface-enhanced Raman scattering; magnetic aggregation; on-site detection
Online: 15 May 2017 (11:53:34 CEST)
We report magnetic silver nanoshells (M AgNSs) that have both magnetic and SERS properties for SERS-based detection. The M AgNSs are composed of hundreds of Fe3O4 nanoparticles for rapid accumulation and bumpy silver shell for sensitive SERS detection by near-infrared laser excitation. The intensity of the SERS signal from the M AgNSs was strong enough to provide single particle-level detection. We obtained much stronger SERS signal intensity from the aggregated M AgNSs than from the non-aggregated AgNSs. 4-Fluorothiophenol was detected at concentrations as low as 1 nM, which corresponds to 0.16 ppb. The limit of detection for tetramethylthiuram disulfide was 10 μM, which corresponds to 3 ppm. The M AgNSs can be used to detect trace amounts of organic molecules using a portable Raman system.
ARTICLE | doi:10.20944/preprints202311.0114.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: Raman; Ultrasonic relaxation spectroscopy; Molecular orbital calculations; Hexamethylenetetramine; Aggregation mechanism
Online: 2 November 2023 (08:17:34 CET)
Raman scattering has been employed to study in detail the concentration dependence of the vibrational modes for the hexamethylenetetramine (HMTA) aqueous solutions. The formation of protonated and/or aggregated species has been clarified by comparing the experimental with the theoretically predicted vibrational spectra by means of quantum mechanical calculations. The analysis has shown that the vibrational modes of the solutions arise from a contribution of the vibrational modes of the HMTA self-aggregates and hetero-aggregates of HMTA with water molecules that are formed in the low- and intermediate-concentration region, respectively. The protonation of HMTA is ruled out due to the large differences between the experimental and the theoretically calculated spectra of the protonated molecules of HTMA in the fingerprint region. In the low-concentration solutions, the hetero-aggregation reaction of HMTA with water is the dominant mechanism, while at higher concentrations a self-aggregation mechanism occurs. Ultrasonic absorption and velocity measurements were carried out for hexamethylenetetramine aqueous solutions. The acoustic spectra reveal the presence of only one single Debye-type relaxation process that is assigned to the aggregation mechanism of HMTA. The sound absorption data follow two different dependencies on HMTA mole fraction. The crossover 0.018 mole fraction signifies two separate regions with distinct structural characteristics. The relaxation mechanism observed in dilute solutions is attributed to hetero-association of HMTA with water molecules, while at higher concentrations the observed relaxation process is assigned to the self-association reaction of HMTA molecules. This structural transformation is also reflected in several physicochemical properties of the system, including the kinematic viscosity, the mass density, the sound speed, and the adiabatic compressibility of the HMTA aqueous solutions. The combination of vibrational and acoustic spectroscopies with molecular orbital calculations allowed us to disentangle the underlying processes and to elucidate the observed relaxation mechanism in the HMTA aqueous solutions.
REVIEW | doi:10.20944/preprints202308.2106.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: Methane; Methanol; MOF; Spectroscopy; XAS; IR; Raman; Mössbauer; EPR; XPS
Online: 31 August 2023 (10:03:59 CEST)
The direct methane to methanol (MTM) oxidation is a grand challenge in catalysis, with profound economical implications for the modern chemical industry. Bioinspired metal-organic frameworks (MOFs) with active iron and copper sites have been emerging very recently as innovative catalytic platforms to accomplish the MTM conversion under mild conditions. This review discusses the current state of the art regarding the application of MOFs with iron and copper catalytic centers to perform the MTM reaction, with a focus on the diverse spectroscopic techniques used to unveil the electronic and structural properties of the MOF catalysts at a microscopic level. We explore the synthetic strategies employed to incorporate iron and copper sites into different MOF topologies, the efficiency and selectivity of the iron- and copper-bearing MOF catalysts, and the ensuing MTM reaction mechanisms proposed on the basis of spectroscopic characterization supported by theory. In particular, we evidence how the combination of complementary spectroscopic tools probing different regions of the electromagnetic spectrum is particularly useful to reach a satisfactory understanding of the key reaction pathways and intermediates. Finally, we provide a critical perspective on future directions to advance the use of MOFs to accomplish the MTM reaction.
ARTICLE | doi:10.20944/preprints202003.0008.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: 2D materials; photodetectors; oxidation; TiS3; TiO2; Raman spectroscopy; DFT GW
Online: 1 March 2020 (03:43:01 CET)
In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS3), a layered semiconductor that attracted much attention recently thanks to its quasi-1D electronic and optoelectronic properties and its direct bandgap of 1.1 eV. Heating TiS3 in air above 300 °C gradually converts it into TiO2, a semiconductor with a wide bandgap of 3.2 eV with applications in photo-electrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of individual TiS3 nanoribbons and its influence on the optoelectronic properties of TiS3-based photodetectors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS3 devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase of the bandgap of titanium oxysulfide (TiO2-xSx) when increasing the amount of oxygen and reducing the amount of sulfur.
ARTICLE | doi:10.20944/preprints201904.0066.v1
Subject: Chemistry And Materials Science, Applied Chemistry Keywords: Raman spectra; mixed pesticides; apple; correction method; rapid; real-time
Online: 5 April 2019 (15:17:24 CEST)
In the study, a new correction method was applied to reduce error during detection on mixed pesticide residue in apples by using Raman spectra. Combined with self-built pesticide residues detection system by Raman spectroscopy and the application of surface enhancement technology, rapid real-time qualitative and quantitative analysis of deltamethrin and acetamiprid residues in apples can be applied effectively. In quantitative analysis, compared with the intensity value of characteristic peaks of single pesticide with same concentration, the intensity value of characteristic peaks of the two pesticides decreased after mixing the pesticides, which interferes the results severely. By comparing the difference in the intensity of characteristic peaks of single and mixed pesticides, a correction method is proposed to eliminate the influence of pesticides mixture. Characteristic peak intensity values of gradient concentration pesticide from 10-1 g•kg-1 to 10-6 g•kg-1 and Lagrangian interpolation are applied in the correction method. And a smooth surface is applied to describe the correction ratio of characteristic peak intensity. Through detecting the characteristic peak intensity values of the mixed pesticide, correction ratio will be obtained. Then real values of the peak intensity of pesticides and the content of each component of the mixed pesticide will be acquired by the correction method. Correlation coefficient of model validation exceeds 0.88 generally and Root Mean Square Error also decreases obviously after correction, which proved the reliability of the method.
ARTICLE | doi:10.20944/preprints201811.0364.v1
Subject: Physical Sciences, Applied Physics Keywords: Bio-sensing, Extinction cross-section, Nano-particles, Plasmons, Raman scattering.
Online: 15 November 2018 (14:54:58 CET)
In this paper, the far field and near field optical responses of a gold nanoparticle are studied and simulated numerically. The electromagnetic field was excited by an electric dipole located near one end of the nanorod, which is used to model the emission of a quantum dot. Another excitation method was also simulated in which an incident plane wave is used. The excitation of dark plasmon modes of the gold nanorod is presented. The Poynting equation was solved numerically to study the influence of the gold nanorod on the dipole radiative power. In addition, the extinction cross section of the gold nanoparticle illuminated by the incident plane wave was calculated to estimate the amount of the scattered and absorbed light.
ARTICLE | doi:10.20944/preprints201811.0039.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: poly-Si TFT; FT-IR; Raman; surface passivation; leakage current
Online: 2 November 2018 (09:32:53 CET)
We report the effects of surface passivation by depositing a hydrogenated amorphous silicon (a-Si:H) layer on the electrical characteristics of low temperature polycrystalline silicon thin film transistors (LTPS TFTs). The a-Si:H layer was optimized by hydrogen dilution and its structural and electrical characteristics were investigated. The a-Si:H layer in the transition region between a-Si:H and µc-Si:H resulted in superior device characteristics. Using an a-Si:H passivation layer, the field-effect mobility of the LTPS TFT was increased by 78.4% compared with a conventional LTPS TFT. Moreover, the leakage current measured at a VGS of 5 V was suppressed because the defect sites at the poly-Si grain boundaries were well passivated. Our passivation layer, which allows thorough control of the crystallinity and passivation-quality, should be considered a candidate for high performance LTPS TFTs.
ARTICLE | doi:10.20944/preprints202308.0030.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: BNT thin film; X-ray diffraction; AFM; Raman spectroscopy, Energy storage
Online: 1 August 2023 (09:52:52 CEST)
Bismuth sodium titanate thin films (BNT) were deposited on Pt/SiN substrates by Sol-Gel spin coating technique under O2 atmosphere. Microstructural, structural, and electrical properties of the obtained film were investigated. Scanning electron microscopy and atomic force microscopy micrographs were used to analyze the microstructure of the films. Furthermore, EDX analysis revealed a Na-deficient composition for the obtained film. X-ray diffraction and Raman spectroscopy allowed the identification of a pure perovskite BNT phase. Dielectric, ferroelectric, and leakage current measurements revealed good frequency stability of the dielectric constant and dielectric losses for BNT thin film. The results are discussed in terms of Na-deficiency effects on the defect structure of BNT. Further, the film showed attractive electrostatic energy storage properties with energy density that exceeds 1.04 J/cm3 under E = 630 kV/cm.
ARTICLE | doi:10.20944/preprints202307.1556.v1
Subject: Chemistry And Materials Science, Chemical Engineering Keywords: bimetallic catalyst; Raman spectroscopy; TPR; palladium hydride; chemisorption; DRIFTS; STEM-EDX
Online: 25 July 2023 (10:03:28 CEST)
PdRe/Al2O3 catalysts are highly selective for hydrogenation of furfural to furfuryl alcohol (FAL). Moreover, synergy between the metals can result in greater specific activity (higher turnover frequency, TOF) than exhibited by either metal alone. Bimetallic catalyst structure depends strongly on the metal precursors employed and their addition sequence to the support. In this work, PdRe/Al2O3 catalysts were prepared by: (i) co impregnation (CI) and sequential impregnation (SI) of Al2O3 using HReO4 and Pd(NO3)2, (ii) SI using NH4ReO4 and [Pd(NH3)4(NO3)2], (iii) HReO4 addition to a reduced and passivated Pd/Al2O3 catalyst, and (iv) impregnation with the double complex salt (DCS), [Pd(NH3)4(ReO4)2]. Raman spectroscopy and temperature-programmed reduction (TPR) evidence larger supported PdO crystallites in catalysts prepared using Pd(NO3)2 than [Pd(NH3)4(NO3)2]. Surface [ReO4]- species detected by Raman exhibit TPR peak temperatures from ranging 85 to 260°C (versus 375°C for Re/Al2O3). After H2 reduction at 400°C, the catalysts were characterized by chemisorption, temperature-programmed hydride decomposition (TPHD), CO diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and scanning transmission electron microscopy (STEM) with energy-dispersive x-ray (EDX) spectroscopy. The CI catalyst containing supported Pd-Re alloy crystallites had a TOF similar to Pd/Al2O3 but higher (61%) FAL selectivity. In contrast, catalysts prepared by methods (ii-iv) containing supported Pd-Re nanoparticles exhibit higher TOFs and up to 78% FAL selectivity.
ARTICLE | doi:10.20944/preprints202307.1087.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Raman spectrum; Denoising; Variational mode decomposition; Empirical mode decomposition; Mode mixing
Online: 17 July 2023 (09:27:33 CEST)
As a fast and nondestructive spectroscopic analysis technique, Raman spectroscopy has been widely applied in chemistry. However, noise is usually unavoidable in Raman spectra. Hence, denoising is an important step before Raman spectral analysis. A novel spectral denoising method based on variational mode decomposition (VMD) was introduced to solve the above problem. The spectrum is decomposed into a series of modes (uk) by VMD. Then, the high frequency noise modes are removed and the remaining modes are reconstructed to obtain the denoised spectrum. The proposed method was verified by two artificial noised signals and two actual Raman spectra. As comparison, empirical mode decomposition (EMD), Savitzky-Golay (SG) smoothing and discrete wavelet transformation (DWT) are also investigated. At the same time, signal-to-noise ratio (SNR) was introduced as evaluation indicators to verify the performance of the proposed method. The results show that compared with EMD, VMD can significantly improve mode mixing and endpoint effect. Some information of the small sharp peak is lost after VMD denoising. However, VMD lost fewer information than that of EMD, SG smoothing and DWT. Moreover, the Raman spectrum by VMD denoising is more excellent than that of EMD, SG smoothing and DWT in terms of visualization and SNR. Therefore, VMD provides superior denoising capabilities for Raman spectra.
ARTICLE | doi:10.20944/preprints202307.0126.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Levantine rock art, µ-Raman spectroscopy, µ-EDXRF, XRD, sulfates, biodeterioration
Online: 4 July 2023 (09:49:55 CEST)
In this work, some micro-samples belonging to the open-air rock art site of Cueva de la Vieja (Alpera, Albacete, Spain) were analysed. These samples were collected after and before a desalination treatment carried out with the aim of removing a whitish layer of concretion that affected the painted panel. The diagnostic study was performed to study the conservation state of the panel and then to confirm the effectiveness of treatment. Micro energy dispersive X-ray fluorescence spectrometry, Raman spectroscopy and X-ray diffraction were employed for the characterization of the degradation product as well as that of mineral substrate and pigments. The micro-samples analysis demonstrated that the painted layer was settled on a dolomitic limestone with silicon aggregates and aluminosilicates as well as iron oxides. The whitish crust was composed by sulfate compounds like gypsum (CaSO4·2H2O) with minor amount of epsomite (MgSO4.7H2O). An extensive phenomenon of biological activity was demonstrated since, in almost all the samples analysed, the presence of calcium oxalates monohydrate (CaC2O4H2O) and dehydrate (CaC2O42H2O) were found. Probably the presence of both calcium oxalates had favoured the conservation of pictographs. In addition, some carotenoids pigments, scytonemin (C36H20N2O4) and astaxanthin (C40H52O4) were characterized both by Raman spectroscopy and by X-ray diffraction. Hematite was found as a pigment voluntarily used for the painting of the panels used in mix with hydroxyapatite and amorphous carbon. The results of the analyses of the samples taken after the cleaning treatment confirmed a substantial decrease in sulphate patina on the panel surface.
ARTICLE | doi:10.20944/preprints202304.0620.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Manganese phthalocyanine (MnPc); Ultrasonic spray pyrolysis; UV/Vis; Raman; XRD; SEM
Online: 20 April 2023 (07:43:57 CEST)
In this work, we report manganese phthalocyanine (MnPc) films obtained by ultrasonic spray-pyrolysis technique at 40°C deposited on glass substrate subjected to thermal annealing at 100 °C and 120°C. The MnPc films were characterized by UV/Vis spectroscopy, Raman spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The absorption spectra of the MnPc films were studied in a wavelength range from 200 to 850 nm, where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The optical energy band (Eg) was calculated by the Tauc equation. It was found that for these MnPc films, the Eg has the values of 4.41, 4.46 and 3.58 eV corresponding to as deposited, annealing 100°C and 120°C, respectively. The Raman spectra of the films showed their characteristic vibrational modes of the MnPc films. In X-ray diffractograms of these films, the characteristic diffraction peaks of a metallic phthalocyanine are observed, presenting a monoclinic phase. SEM images of these films were studied in cross section obtaining thicknesses of 2, 1.2 and 0.3 μm to as deposited, annealing 100°C and 120°C, successively. Also, in the SEM images of these films, both the average particle sizes ranging from 4 to 0.041 µm and the average diameter from 4.8 to 0.091 μm were obtained. The results agree with those reported in the literature for MnPc films deposited with other techniques.
ARTICLE | doi:10.20944/preprints202106.0156.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: X-ray diffraction; CeO2; TiO2; crystallite size; strain; TEM; μ-Raman
Online: 7 June 2021 (09:25:14 CEST)
Various crystallite size estimation methods were used to analyze X-ray diffractograms of spherical cerium dioxide and donut-like titanium dioxide anatase nanoparticles aiming to evaluate their reliability and limitations. The microstructural parameters were estimated from Scherrer, Monshi, Williamson-Hall, and their variants: i) uniform deformation model, ii) uniform strain deformation model, and iii) uniform deformation energy density model, and also size-strain plot, and Halder-Wagner method. For that, and improved systematic Matlab code was developed to estimate the crystallite sizes and strain, and the linear regression analysis was used to compare all the models based on the coefficient of determination, where the Halder Wagner method gave the highest value (close to 1). Therefore, being the best candidate to fit the X-ray Diffraction data of metal-oxide nanoparticles. Advanced Rietveld was introduced for comparison purposes. Refined microstructural parameters were obtained from a nanostructured 40.5 nm Lanthanum hexaboride nanoparticles and correlated with the above estimation methods and transmission electron microscopy images. In addition, electron density modelling was also studied for final refined nanostructures, and μ-Raman spectra were recorded for each material estimating the mean crystallite size and comparing by means of a phonon confinement model.
ARTICLE | doi:10.20944/preprints202104.0511.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: dacarbazine, triazene, anticancer properties, 3d-metal complexes, spectroscopy (IR, Raman), NMR
Online: 19 April 2021 (16:59:49 CEST)
: Dacarbazine, DAC, 5-(3,3-dimethyltriazeno)imidazol-4-carboxamideis is an imidazole-carboxamide derivative, that is structurally related to purines. DAC belongs to the triazene compounds, which are a group of alkylating agents with antitumour and mutagenic properties. DAC is a non-cell cycle specific drug, active on all phases of cellular cycle. In the frame of this work the 3d-metal complexes (cobalt and copper) with dacarbazine were synthesized. Their spectroscopic properties by the use of FT-IR, FT-Raman and 1HNMR were studied. The structures of dacarbazine and its complexes with copper(II) and cobalt(II) were calculated using DFT methods. The effect of metals on the electronic charge distribution of dacarbazine was discussed on the basis of calculated NBO atomic charges. The reactivity of metal complexes in relation to ligand alone was estimated on the basis of calculated energy of HOMO and LUMO orbitals. The aromaticity of imidazole ring in dacarbazine and the complexes was compared (on the basis of calculated geometric indices of aromaticity). Thermal stability of the investigated 3d-metal complexes with dacarbazine and the products of their thermal decomposition were analyzed.
Subject: Chemistry And Materials Science, Biomaterials Keywords: Mining tailings; Tantalum; X-Ray diffraction; Raman spectroscopy; Scanning electron microscopy.
Online: 23 October 2020 (12:22:54 CEST)
In this work, a deep characterization of the properties of K6Ta10.8O30 microrods has been performed. The starting material used to grow the microrods has been recovered from mining tailings coming from the Penouta Sn-Ta-Nb deposit, located in the north of Spain. The recovered material has been submitted to a thermal treatment to grow the microrods. Then, they have been characterized by scanning electron microscopy, X-ray diffraction, micro-Raman and micro-photoluminescence. The results of our study confirm that the K6Ta10.8O30 microrods have a tetragonal tungsten bronze-like crystal structure, which can be useful for ion-batteries and photocatalysis.
ARTICLE | doi:10.20944/preprints201902.0119.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: HiPIMS; silicon carbide; aluminum nitride; thin film; RBS; GIXRD; Raman spectroscopy
Online: 13 February 2019 (15:33:09 CET)
Many strategies have been developed for the synthesis of silicon carbide (SiC) thin films on silicon (Si) substrates by plasma-based deposition techniques, especially plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering, due to importance of these materials for microelectronics and related fields. A drawback is the large lattice mismatch between SiC and Si. The insertion of a thin aluminum nitride (AlN) buffer layer between them has been shown useful to overcome this problem. Herein, the high-power impulse magnetron sputtering (HiPIMS) technique was used to grow SiC thin films on AlN/Si substrates. Furthermore, the SiC films were also grown on Si substrates. Comparisons of the structural and chemical properties of SiC thin films grown on the two types of substrates allowed us to evaluate the influence of AlN buffer layer on such properties. The chemical composition and stoichiometry of the samples were investigated by Rutherford backscattering spectrometry (RBS) and Raman spectroscopy, while the crystallinity was characterized by grazing incidence X-ray diffraction (GIXRD). Our set of results evidenced the versatility of HiPIMS technique to produce polycrystalline SiC thin films at near room temperature only varying the discharge power. In addition, this study opens up a feasible route for the deposition of crystalline SiC films with a good structural quality using AlN buffer layer.
REVIEW | doi:10.20944/preprints201810.0012.v1
Subject: Medicine And Pharmacology, Other Keywords: noninvasive glucose measurement; IR spectroscopy; Raman spectroscopy; photoacoustic spectroscopy; microwave sensing
Online: 1 October 2018 (14:04:05 CEST)
Diabetic patients need long-term and frequent glucose monitoring to assist in insulin intake. The current finger-prick devices are painful and costly which make noninvasive glucose sensors highly demanded. In this review paper, we discuss several advanced electromagnetic (EM) wave based technologies for noninvasive glucose measurement, including infrared (IR) spectroscopy, photoacoustic (PA) spectroscopy, Raman spectroscopy, fluorescence, optical coherent tomography (OCT) and microwave sensing. Development and progress of each method are discussed regarding fundamental principle, system setup and experimental results. Despite the promising achievements reported previously, there is no established product to obtain FDA approval or survive marketing test. Limitations and prospects of these techniques are discussed at the end of this review.
ARTICLE | doi:10.20944/preprints201809.0547.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: ice X; vibrational spectrum; first-principles DFT; Raman scattering; IR absorption
Online: 27 September 2018 (13:25:06 CEST)
A typical vibrational spectrum in the ice phase has four separate bands: translation, libration, bending and stretching. Ice X, the final ice phase under high pressure, shows an exotic vibrational spectrum. Theoretically, an ideal crystal of ice X only has one peak at 998 cm-1 for Raman scattering and two peaks at 450 cm-1 and 1507 cm-1 for infrared absorption in this work. These three characteristic peaks are indicators of the phase transition between ice VII/VIII and ice X. Despite much experimental and theoretical work on ice X, only this study has clearly indicated these characteristic peaks in the region of the IR band. The phonon density of states shows quite different features than ice VIII, which could be verified by inelastic neutron scattering in the future. The dynamic processes of 15 vibrational normal modes are discussed and the typical hydrogen bonds are missing.
ARTICLE | doi:10.20944/preprints202311.1467.v1
Subject: Environmental And Earth Sciences, Pollution Keywords: microplastics, polyethylene, polystyrene, polypropylene, characterization, identification, FT-IR, Raman, Somesul Mic River
Online: 23 November 2023 (04:54:42 CET)
Microplastics (MPs) pollution has become a persisting problem over the last decades and a critical issue for environmental protection and human health. In this context any scientific data able to reveal the MPs presence and to improve the characterization and identification in different systems is valuable. The aim of this paper was to assess available techniques for determining MPs in real freshwater samples and subsequently to highlight the occurrence and type of MPs in the study case area (Somesul Mic River). The specific objectives of the study were: i) MPs separation and visual characterization; ii) microscopic analyses and morphological characterization of MPs; iii) Raman and FT-IR spectroscopic identification of MPs. MPs sampling was performed from the fresh water and sediment using planktonic nets and sieves with different mesh sizes (20 to 500µm). After digestion with hydrogen peroxide, the MPs characterization was performed using both classical microscopic techniques as well as scanning electron microscopy (SEM). For the MPs identification, Raman and FT-IR spectrometry techniques were used. Large (1-5 mm) and small (1 µm to 1 mm) MPs were observed in the shape of fibers, fragments, foam, foils and spheres in various colors (red, green, blue, purple, pink, white, black, transparent, opaque). Polymers were identified related to scientific literature and reference spectra. The presence of polyethylene (PE), polypropylene (PP) and polystyrene (PS) was registered for all sampling point. The MPs laboratory investigations have raised some issues regarding the identification of MPs particles with the size smaller than 500µm, being characterized especially under microscope. Small MPs particle dispersed on cellulose filter were identified using micro-Raman spectroscopy highlighting the same type of polymers. The results showed that both spectrometric methods Raman or FT-IR confirm the identification of the same type of polymers. No differences were registered between the sampling points due to the widespread presence of MPs. The sediments samples presented a greater abundance compared to the water samples. Overall, it is necessary to continue the optimization of the MPs separation protocol and identification according to the complexity of samples, mainly due to the limitation and lack of spectral databases.
ARTICLE | doi:10.20944/preprints202112.0450.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: polymerization catalysis; machine learning; nanoclusters; DFT; Raman spectrum; IR spectrum; Lewis bases
Online: 28 December 2021 (14:04:10 CET)
Understanding the structure and properties of MgCl2/TiCl4/ID nanoclusters is a key to uncover the origin of Ziegler-Natta catalysis. In this work MgCl2/TiCl4 nanoplatelets derived by machine learning and DFT calculations have been used to model the interaction with ethyl-benzoate EB (as internal donor) with available exposed sites of binary TixCly/MgCl2 systems. The influence of vicinal Ti2Cl8 and coadsorbed TiCl4 on energetic, structural and spectroscopic behaviour of EB has been considered. The adsorption of homogeneous-like TiCl4EB and TiCl4(EB)2 at the various surface sites have been also simulated. Calculations have been carried out by employing B3LYP-D2 and M06 functionals. The adducts have been characterized by computing IR and Raman spectra that have been found to provide specific fingerprints useful to identify surface species; IR spectra have been successfully compared to available experimental data.
ARTICLE | doi:10.20944/preprints202109.0317.v1
Subject: Biology And Life Sciences, Cell And Developmental Biology Keywords: EBPR; polyphosphate chain length; NMR; polyacrylamide gel electrophoresis; single-cell Raman spectroscopy
Online: 17 September 2021 (12:50:48 CEST)
Polyphosphate (polyP) accumulating organisms (PAOs) are the key agent to perform enhanced biological phosphorus removal (EBPR) activity, and intracellular polyP plays a key role in this process. Potential associations between EBPR performance and the polyP structure have been suggested, but are yet to be extensively investigated, mainly due to the lack of established methods for polyP characterization in the EBPR system. In this study, we explored and demonstrated that single-cell Raman spectroscopy (SCRS) can be employed for characterizing intracellular polyPs of PAOs in complex environmental samples such as EBPR systems. The results, for the first time, revealed distinct distribution patterns of polyP length (as Raman peak position) in PAOs in lab-scale EBPR reactors that were dominated with different PAO types, as well as among different full-scale EBPR systems with varying configurations. Furthermore, SCRS revealed distinctive polyP composition/features among PAO phenotypic sub-groups, which are likely associated with phylogenetic and/or phenotypic diversity in EBPR communities, highlighting the possible resolving power of SCRS at the microdiversity level. To validate the observed polyP length variations via SCRS, we also performed and compared bulk polyP length characteristics in EBPR biomass using conventional polyacrylamide gel electrophoresis (PAGE) and solution 31P nuclear magnetic resonance (31P-NMR) methods. The results are consistent with the SCRS findings and confirmed the variations in the polyP lengths among different EBPR systems. Compared to conventional methods, SCRS exhibited advantages as compared to conventional methods, including the ability to characterize in situ the intracellular polyPs at subcellular resolution in a label-free and non-destructive way, and the capability to capture subtle and detailed biochemical fingerprints of cells for phenotypic classification. SCRS also has recognized limitations in comparison with 31P-NMR and PAGE, such as the inability to quantitatively detect the average polyP chain length and its distribution. The results provided initial evidence for the potential of SCRS-enabled polyP characterization as an alternative and complementary microbial community phenotyping method to facilitate the phenotype-function (performance) relationship deduction in EBPR systems.
ARTICLE | doi:10.20944/preprints202010.0071.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: ethane-diols; methoxy and dimethoxy ethane; liquid structure; hydrogen bond, XRD; Raman
Online: 5 October 2020 (11:30:46 CEST)
In this study, we report a detailed experimental and theoretical investigation of three glycols, namely ethane-1,2-diol, 2-methoxyethan-1-ol and 1,2-dimethoxy ethane. For the first time, the X-Ray spectra of the latter two liquids was measured at room temperature, and they were compared with the newly measured spectrum of ethane-1,2-diol. The experimental diffraction patterns were interpreted very satisfactorily with molecular dynamics calculations, and suggest that in liquid ethane-1,2-diol most molecules are found in gauche conformation, with intramolecular hydrogen bond between the two hydroxyl groups. Intramolecular H-bonds are established in the mono-alkylated diol, but the interaction is weaker. The EDXD study also evidences strong intermolecular hydrogen-bond interactions, with short O···O correlations in both systems, while longer methyl-methyl interactions are found in 1,2-dimethoxy ethane. X-Ray studies are complemented by micro Raman investigations at room temperature and at 80°C, that confirm the conformational analysis predicted by X-Ray experiments and simulations.
ARTICLE | doi:10.20944/preprints202309.0988.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: germanium; thin films; ultrashort infrared laser annealing; crystallization; Raman spectroscopy; non-refractory substrates
Online: 14 September 2023 (11:18:28 CEST)
Amorphous germanium films on non-refractory glass substrates were annealed by ultrashort near-infrared (1030 nm, 1.4 ps) and mid-infrared (1500 nm, 70 fs) laser pulses. Crystallization of germanium irradiated at a laser energy density (fluence) range from 25 to 400 mJ/cm2 under single-shot and multi-shot conditions was investigated using Raman spectroscopy. The dependence of the fraction of the crystalline phase on the fluence was obtained for picosecond and femtosecond laser annealings. The regimes of almost complete crystallization of germanium films over the entire thickness are obtained (from the analysis of Raman spectra with excitation of 785 nm laser). The possibility of scanning laser processing is shown, which can be used to create films of micro and nanocrystalline germanium on flexible substrates.
ARTICLE | doi:10.20944/preprints202111.0002.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: monochalcogenides; germanium sulfide; photoluminescence; reflectance contrast; excitons; Raman scattering; Density Fuctional Theory; phonons
Online: 1 November 2021 (10:18:02 CET)
The optical response of bulk germanium sulfide (GeS) is investigated systematically using different polarization-resolved experimental techniques, such as photoluminescence (PL), reflectance contrast (RC), and Raman scattering (RS). It is shown that while the low-temperature (T=5 K) optical band-gap absorption is governed by a single resonance related to the neutral exciton, the corresponding emission is dominated by the disorder/impurity- and/or phonon-assisted recombination processes. Both the RC and PL spectra are found to be linearly polarized along the armchair direction. The low and room (T=300 K) temperature RS spectra consist of six Raman peaks identified with the help of Density Fuctional Theory (DFT) calculations: Ag1, Ag2, Ag3, Ag4, B1g1, and B1g2, which polarization properties are studied under four different excitation energies. We found that the polarization orientations of the Ag2 and Ag4 modes under specific excitation energy can be useful tools to determine the GeS crystallographic directions: armchair and zigzag.
ARTICLE | doi:10.20944/preprints202001.0351.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Optical biopsy; Raman spectroscopy; Micro-optics; Ultrafast laser assisted etching; Femtosecond laser micromaching
Online: 29 January 2020 (10:38:18 CET)
Optical biopsy describes a range of medical procedures in which light is used to investigate disease in the body, often in hard-to-reach regions via optical fibres. Optical biopsies can reveal a multitude of diagnostic information to aid therapeutic diagnosis and treatment with higher specificity and shorter delay than traditional surgical techniques. One specific type of optical biopsy relies on Raman spectroscopy to differentiate tissue types at the molecular level and has been used successfully to stage cancer. However, complex micro-optical systems are usually needed at the distal-end to optimise the signal-to-noise properties of the Raman signal collected. Manufacturing these devices remains a critical challenge, particularly in a way suitable for large scale adoption. In this paper, we describe a novel fibre-fed micro-optic system designed for efficient signal delivery and collection during a Raman spectroscopy based optical biopsy. Crucially, we fabricate the device using a direct-laser-writing technique known as ultrafast laser assisted etching which is scalable and allows components to be aligned passively. The Raman probe has a sub-millimetre diameter and offers confocal signal collection with 71.3 ± 1.5% collection efficiency over a 0.8 numerical aperture. Proof of concept spectral measurements were performed on mouse intestinal tissue and compared with results obtained using a commercial Raman microscope.
ARTICLE | doi:10.20944/preprints202311.0491.v1
Subject: Physical Sciences, Optics And Photonics Keywords: surface-enhanced Raman scattering; enhancement factor; optical attenuation; spectral distortion; baseline; effective medium theory
Online: 7 November 2023 (16:59:59 CET)
In this paper, I present a comprehensive theoretical framework for understanding surface-enhanced Raman scattering (SERS) measurements in both solution and thin film setups, focusing on electromagnetic enhancement principles. Two prevalent types of SERS substrates found in the literature are investigated: plasmonic colloidal particles, including spherical and spheroid nanoparticles, nanoparticle diameters, and thin-film-based SERS substrates like ultra-thin substrates, bundled nanorods, plasmonic, and porous thin films. The investigation explores the impact of analyte adsorption, orientation, and the polarization of the excitation laser on effective SERS enhancement factors. Notably, it considers the impact of analyte size on the SERS spectrum, by examining scenarios where the analyte is significantly smaller or larger than the hot-spot dimensions. The analysis also incorporates optical attenuations arising from the optical properties of the analyte and the SERS substrates. The findings provide possible explanations for many observations made in SERS measurements, such as variations in relative peak intensities during SERS assessments, reductions in SERS intensity at high analyte concentrations, and the occurrence of significant baseline fluctuations. The study offers valuable guidance for optimizing SERS substrate design, enhancing SERS measurements, and improving the quantification of SERS detection.
ARTICLE | doi:10.20944/preprints202309.1331.v1
Subject: Chemistry And Materials Science, Electronic, Optical And Magnetic Materials Keywords: lab-on-fiber sensor; Ag/Au nanocap arrays; surface-enhanced Raman scattering; polystyrene nanospheres
Online: 20 September 2023 (14:00:46 CEST)
Surface-enhanced Raman spectroscopy (SERS) can boost the pristine Raman signal by ~ 108 times that could be exploited for producing innovative sensing devices with advanced properties. However, the inherent complexity of SERS systems restricts their further applications in rapid detection, especially in situ detection in narrow aera. Here, we construct an efficient and flexible SERS-based LOP sensor by integrating Ag/Au nanocap arrays obtained by Ag/Au coating polystyrene nanospheres on the optical fiber face. We obtain rich “hotspots” at the nanogaps between neighboring nanocaps and further achieve the excellent SERS performance with the assistance of laser induced thermophoresis on the metal film that can achieve high efficiency aggregation of detected molecules. We achieve a high Raman enhancement with a low detection limitation of 10-7 mol/L for the most efficient samples based on the above sensor. This sensor also exhibits good repeatability and stability under multiple detections, revealing the potential application in situ detection based on the reflexivity of optical fiber.
ARTICLE | doi:10.20944/preprints202010.0619.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: amorphous silicon; polycrystalline silicon; thin films; laser-induced annealing; femtosecond laser pulses; Raman spectroscopy
Online: 29 October 2020 (14:44:58 CET)
Amorphous silicon (α-Si) film present an inexpensive and promising material for optoelectronic and nanophotonic applications. Its basic optical and optoelectronic properties are known to be improved via phase transition from amorphous to polycrystalline phase. Infrared femtosecond laser radiation can be considered as a promising nondestructive and facile way to drive uniform in-depth and lateral crystallization of α-Si films that are typically opaque in UV-visible spectral range. However, so far only a few studies reported on utilization of near-IR radiation for laser-induced crystallization of α-Si providing no information regarding optical properties of the resultant polycrystalline Si films. The present work demonstrates efficient and gentle single-pass crystallization of α-Si films induced by their direct irradiation with near-IR femtosecond laser pulses coming at sub-MHz repetition rate. Comprehensive analysis of morphology and composition of laser-annealed films by atomic-force microscopy, optical, micro-Raman and energy-dispersive X-ray spectroscopy, as well as numerical modeling of optical spectra, confirmed efficient crystallization of α-Si and high-quality of the obtained films. Moreover, we highlight localized laser-driven crystallization of α-Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.
ARTICLE | doi:10.20944/preprints201804.0277.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: 4-coordinated Si; 6-coordinated Si; MgAl2O4-spinel; Mg2SiO4-ringwoodite; Raman spectroscopy; Si-disordering
Online: 23 April 2018 (08:37:36 CEST)
A series of Si-bearing MgAl2O4-spinels were synthesized at 1500-1650 °C and 3–6 GPa. These spinels had SiO2 contents up to ~1.03 wt%, and showed a substitution mechanism of Si4+ + Mg2+ = 2Al3+. Unpolarized Raman spectra were collected from polished single grains, and displayed a set of well-defined Raman peaks at ~610, 823, 856 and 968 cm-1 which had not been observed before. Aided with the Raman features of natural Si-free MgAl2O4-spinel, synthetic Si-free MgAl2O4-spinel, natural low quartz, synthetic coesite, synthetic stishovite and synthetic forsterite, we infer that these Raman peaks should belong to the SiO4 groups. The relations between the Raman intensities and SiO2 contents of the Si-bearing MgAl2O4-spinels suggest that at some P-T conditions some Si must adopt the M-site. Unlike the SiO4 groups with very intense Raman signals, the SiO6 groups are largely Raman-inactive. We have further found that the Si cations primarily appear on the T-site at P-T conditions ≤ ~3–4 GPa and 1500 °C, but attain a random distribution between the T-site and M-site at P-T conditions ≥ ~5–6 GPa and 1630–1650 °C. This Si-disordering process observed for the Si-bearing MgAl2O4-spinels hints that similar Si-disordering might happen to the (Mg,Fe)2SiO4-spinels (ringwoodite), the major phase in the lower part of the mantle transition zone of the Earth and the index mineral for the very strong shock stage experienced by extraterrestrial materials. The likely consequences have been explored.
ARTICLE | doi:10.20944/preprints201611.0008.v1
Subject: Medicine And Pharmacology, Pharmacy Keywords: nitrofurantoin; active pharmaceutical ingredient; 4-aminobenzoic acid; cocrystallization; intermolecular interaction; Raman spectroscopy; terahertz spectroscopy
Online: 1 November 2016 (09:54:24 CET)
Cocrystallizaiton could improve most physicochemical properties of specific active pharmaceutical ingredients, which has great potential in pharmaceutical development. In this study, the cocrystal of nitrofurantoin and 4-aminobenzoic acid was prepared with solid-state (solvent-free or green-chemistry) grinding approach, and the above cocrystal has been characterized by Raman and terahertz vibrational spectroscopic techniques. Spectral results show that the vibrational modes of the cocrystal within the whole spectral region are different from those of the corresponding parent materials. The dynamic process of such pharmaceutical cocrystal formation has also been monitored directly with Raman spectra. These results offer us unique means for characterizing the cocrystal conformation from molecule-level and also provide us rich information about the reaction dynamic of cocrystal formation within pharmaceutical fields.
ARTICLE | doi:10.20944/preprints202311.1788.v1
Subject: Analytical Chemistry, Chemistry And Materials Science Keywords: RAMAN fingerprints; edible vegetable oils; sunflower oil; olive oil; Patter recognition techniques; portable analyser; SORS
Online: 28 November 2023 (08:20:49 CET)
Nowadays, the combination of fingerprinting methodology with friendly environmental and economical analytical instrumentation are becoming increasingly relevant in the food sector. In this study, a highly versatile portable analyser based on Spatially Offset Raman Spectroscopy (SORS) to obtain the edible vegetable oils (sunflower and olive oils) fingerprints was used to evaluate the capability of such fingerprints, obtained quickly, reliable and without any sample treatment, to discriminate/classify the analysed samples. After data treatment, not only HCA and PCA as unsupervised pattern recognition techniques but also SVM, kNN and SIMCA as supervised pattern recognition techniques, showed that the main effect over the discrimination/classification was associated to those regions of RAMAN fingerprint related to the free fatty acids content, especially oleic and linoleic acid. These facts allowed the discrimination attending to the original raw material used in the oil's elaboration. In all the model established, reliable qualimetric parameters were obtained.
SHORT NOTE | doi:10.20944/preprints202305.1869.v1
Subject: Chemistry And Materials Science, Inorganic And Nuclear Chemistry Keywords: 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine; polypyridyl donors; SC-XRD; FT-Raman; DFT; ICl
Online: 26 May 2023 (05:44:34 CEST)
2-(5,6-diphenyl-1,2,4-triazin-3-yl)pyridinium dichloroiodate (I) (1) was synthesized by reacting 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine with ICl in dichloromethane solution. The structural characterization of 1 by SC-XRD analysis was accompanied by elemental analysis, FT-IR, and FT-Raman spectroscopy measurements.
ARTICLE | doi:10.20944/preprints202112.0289.v1
Subject: Chemistry And Materials Science, Physical Chemistry Keywords: molecular recognition; infrared spectroscopy; Raman spectroscopy; supersonic expansion; chirality induction; hydrogen bond topology; cooperativity; chlorination
Online: 17 December 2021 (14:25:55 CET)
Prereactive complexes in noncovalent organocatalysis are sensitive to the relative chirality of the binding partners and to hydrogen bond isomerism. Both effects are present when a transiently chiral alcohol docks on a chiral α-hydroxy ester, turning such 1:1 complexes into elementary, non-reactive model systems for chirality induction in the gas phase. With the help of linear infrared and Raman spectroscopy in supersonic jet expansions, conformational preferences are investigated for benzyl alcohol in combination with methyl lactate, also exploring p-chlorination of the alcohol and the achiral homolog methyl glycolate to identify potential London dispersion and chirality effects on the energy sequence. Three of the four combinations prefer barrierless complexation via the hydroxy group of the ester (association). In contrast, the lightest complex shows predominantly insertion into the intramolecular hydrogen bond, like the analogous lactate and glycolate complexes of methanol. The experimental findings are rationalized with computations and a uniform helicality induction in the alcohol by the lactate is predicted, independent on insertion into or association with the internal lactate hydrogen bond. p-Chlorination of benzyl alcohol has a stabilizing effect on association, because the insertion motif prevents a close contact between the chlorine and the hydroxy ester. After simple anharmonicity and substitution corrections, the B3LYP-D3 approach offers a fairly systematic description of the known spectroscopic data on alcohol complexes with α-hydroxy esters.
ARTICLE | doi:10.20944/preprints201801.0176.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: tourmaline, fluor-elbaite, elbaite, Zn-enrichment, electron microprobe, Raman spectroscopy, granitic pegmatites, Piława Górna, Sudetes
Online: 18 January 2018 (17:00:38 CET)
Tourmalines are a group of minerals which may concentrate various accessory components, e.g. Cu, Ni, Zn, Bi, Ti, Sn. The paper presents fluor-elbaite and elbaite from a dyke of the Julianna pegmatitic system at Piława Górna, at the NE margin of the Bohemian Massif, SW Poland, containing up to 6.32 and 7.37 wt.% ZnO, respectively. Such high amounts of ZnO are almost two times higher than in the second most Zn-enriched tourmaline known to date. The compositions of the Zn-rich tourmalines from Piława Górna, studied by electron microprobe and Raman spectroscopy, correspond to the formulae: (Na0.73Ca0.01•0.25)Σ1(Al1.03Li0.79Zn0.76Fe2+0.33Mn0.09)Σ3Al6B3Si6O27(OH)3(F0.66OH0.34), and (Na0.78Ca0.01•0.21)Σ1(Al1.06Li0.87Zn0.88Fe2+0.10Mn0.09)Σ3Al6B3Si6O27(OH)3(OH0.84F0.16), respectively, with Zn as one of the main octahedral occupants. A comparison with other tourmalines and associated Zn-rich fluor-elbaite and elbaite from the pegmatite indicates that atypically high Zn-enrichment is not a result of Zn-Fe fractionation, but dissolution and reprecipitation induced by a late (Na,Li,B,F)-bearing fluid within the assemblage of gahnite spinel and primary schorl-type tourmaline. This strongly suggests Na-Li-B-F metasomatism of gahnite-bearing mineral assemblages as that is the only environment that can promote crystallization of a hypothetical Zn-dominant tourmaline. The compositions of the Zn-rich fluor-elbaite and elbaite suggest three possible end-members for such a hypothetical tourmaline species: NaZn3Al6B3Si6O27(OH)3(OH), •(Zn2Al)Al6B3Si6O27(OH)3(OH) and Na(Zn2Al)Al6B3Si6O27(OH)3O.
SHORT NOTE | doi:10.20944/preprints201703.0158.v1
Subject: Chemistry And Materials Science, Inorganic And Nuclear Chemistry Keywords: au(I) dithiocarbamate and phosphine complex; Raman spectroscopy; Single crystal X-ray diffraction; DFT calculations
Online: 20 March 2017 (10:00:42 CET)
A gold(I) complex with a triphenylphosphine and a monodentate N,N-dimethyldithiocarbamate ligand was synthesized and characterized by Raman spectroscopy and single crystal X-ray diffraction. DFT calculations (Gaussian 09, PBE1PBE/Lanl2dz) were undertaken for a single complex in the gas-phase. The DFT-optimized structure is in good agreement with the crystal structure and the DFT-calculated Raman spectrum also is in excellent agreement with the experimental spectrum. Assignments of the Raman peaks are based on these DFT calculations. Frontier molecular orbitals were calculated and their nature is discussed.
ARTICLE | doi:10.20944/preprints202310.0573.v1
Subject: Biology And Life Sciences, Life Sciences Keywords: microscopy; optical diffraction tomography; Raman spectroscopy; therapy-induced senescence; cell engulfing; vacuole; cancer; cell-in-cell
Online: 10 October 2023 (05:32:15 CEST)
Wild-type p53 cancer therapy-induced senescent cells frequently engulf and degrade neighboring ones inside a massive vacuole in their cytoplasm. After clearance of the internalized cell, the vacuole persists, seemingly empty, for several hours. Despite large vacuoles being associated with cell death, this process is known to confer a survival advantage to cancer engulfing cells, leading to therapy resistance and tumor relapse. Previous attempts to resolve the vacuolar structure and visualize their content using dyes were unsatisfying for lack of known targets and ineffective dye penetration and/or retain. Here, we overcame this problem by applying optical diffraction tomography and Raman spectroscopy to MCF7 doxorubicin-induced engulfing cells. We demonstrated a real ability of cell tomography and Raman to phenotype complex microstructures, such as cell-in-cells and vacuoles, and detect chemical species in extremely low concentrations within live cells in a completely label-free fashion. We show that vacuoles had a density indistinguishable to the medium, but were not empty, instead contained diluted cell-derived macromolecules, and we could discern vacuoles from medium and cells using their Raman fingerprint. Our approach is useful for the non-invasive investigation of senescent engulfing (and other peculiar) cells in unperturbed conditions, crucial for a better understanding of complex biological processes.
ARTICLE | doi:10.20944/preprints202306.2203.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: zirconium carbide; zirconium dioxide; carbon matrix; graphite; RF plasma; carbonization; thiourea; styrene-divinylbenzene copolymer; Raman spectroscopy
Online: 30 June 2023 (14:57:52 CEST)
Thermal processing of Zr-loaded ion-exchangers is a facile route to synthetize (ZrO2, ZrC)@C composites. The chemical character of the functional groups in the cation exchanger is an essential factor in the composition and properties of the (ZrO2, ZrC)@C composites. In the present paper furnace and RF-thermal plasma processing of ZrOCl2 loaded thiourea-functionalized styrene-divinylbenzene copolymer was investigated that led to various composites containing ZrO2 and ZrC. Depending on the synthesis conditions, different ZrO2@C composites were formed between 1000 and 1400 °C in 2 h, whereas the composite containing ZrC was created at 1400 °C in 8 h. The ratio of ZrO2/ZrC, the prevailing ZrO2 modifications, and the crystallite sizes strongly depend on the synthesis conditions. The ZrC-containing composites formed only at 1400 °C in 8 hours and by the plasma treatment of the ZrO2@C sample prepared in the furnace, resulting in 8 and 16% ZrC content, with 44 and 41 nm ZrC crystallite sizes, respectively. The ZrO2-containing composites (tetragonal, monoclinic, and cubic modifications with 65–88 nm ZrO2 crystallite sizes and 15–43 m2/g BET surface areas, depending on the carbonization temperature) formed in a tube furnace between 1000 and 1400 °C in 2 h. The tube furnace–prepared sample formed at 1400 °C in 8 h contained ZrC, ZrO2 modifications, and amorphous carbon, whereas the plasma-treated sample contained ZrC, ZrO2 modifications, and graphite. All ZrO2@C composites had both amorphous carbon and graphite, and their ratio is temperature-dependent. The carbonaceous compounds of the prepared composites were characterized by Raman spectroscopy, with analysis of the G and D band intensities. XPS studies showed the surface oxidation of ZrC.
ARTICLE | doi:10.20944/preprints202304.0551.v1
Subject: Physical Sciences, Optics And Photonics Keywords: diatom valve; SERS; surface-enhanced Raman scattering; guided-mode resonance; finite element method; hybrid SERS sensors
Online: 19 April 2023 (05:50:08 CEST)
The discovered light modulation capabilities of diatom silicious valves make them an excellent toolkit for photonic devices and applications. In this work, a reproducible surface-enhanced Raman-scattering (SERS) enhancement was achieved with hybrid substrates employing diatom silica valves coated with an ultrathin uniform gold film. Three structurally different hybrid substrates, based on the valves of three dissimilar diatom species, have been compared to elucidate the structural contribution to SERS enhancement. The comparative analysis of obtained results showed that substrates containing cylindrical Aulacoseira sp. valves achieved the highest enhancement up to 14-fold. Numerical analysis based on the frequency domain finite element method was carried out to supplement the experimental results. Our results demonstrate that diatom valves of different shapes can enhance the SERS signal, offering a toolbox for SERS-based sensors, where the magnitude of the enhancement depends on valve geometry and ultrastructure.
ARTICLE | doi:10.20944/preprints202103.0330.v1
Subject: Medicine And Pharmacology, Immunology And Allergy Keywords: Barrett’s esophagus; biomarker; surveillance; screening; surface-enhanced Raman spectroscopy; SERS; complement component; liquid biopsy; lectin; glycoprotein.
Online: 12 March 2021 (08:03:55 CET)
Esophageal adenocarcinoma (EAC) detection relies on endoscopy-biopsy diagnosis, with routine endoscopic surveillance recommended for Barrett’s esophagus (BE) patients. Here, we examine the utility of blood biomarkers in patient risk stratification by translating the EAC blood biomarker Jacalin lectin binding complement C9 (JAC-C9) into a novel microfluidic immunoassay, the EndoScreen Chip. Cohort evaluation (n=46) showed elevated serum total C9 and JAC-C9 in EAC. Logistic regression modeling demonstrated that addition of C9 and JAC-C9 to patient risk factors (age, body mass index and heartburn/reflux history) improved EAC prediction from AUROC of 0.838 to 0.931. Serum JAC-C9 strongly predicted EAC (vs BE OR= 4.6, 95% CI: 1.6-15.6, p = 0.014; vs Healthy OR=4.1, 95% CI:1.2-13.7, p = 0.024) while total C9 was moderately predictive for BE (vs EAC OR=1.4; 95% CI: 1.0-1.8, p = 0.032; vs Healthy OR=0.8; 95% CI: 0.6-1.0, p = 0.039). This translational study demonstrates the potential utility of blood biomarkers in improving triaging for diagnostic endoscopy.
ARTICLE | doi:10.20944/preprints201909.0135.v1
Subject: Physical Sciences, Fluids And Plasmas Physics Keywords: Surface-enhanced Raman spectroscopy (SERS); surface plasmons; Finite-Difference Time-Domain (FDTD) method; electromagnetic (EM) enhancement
Online: 13 September 2019 (12:36:31 CEST)
Giant plasmonic surface enhancement has been observed in gold coated micron sized inverse pyramids entrapping a gold nanoparticle. The amplification of both surface enhanced Raman and photoluminescence signals was found to be dependent on the diameter of trapped gold nanoparticle and around 50-fold enhancement was detected for 250nm diameter sample relatively to the 50nm one. Finite differential time domain simulations, performed to determine the near-field distribution in the structure, showed that when the nanoparticle protrudes into the hotspot zone of the void, coupling of electromagnetic field occurs and the plasmon-related near-field enhancement is concentrated into the close vicinity of the nanoparticle, mainly into the close gaps around the tangential points of the curved sphere and the flat pyramid surface. This results in a more than 15 times increase of the near-field intensity, compared to the empty void.
ARTICLE | doi:10.20944/preprints201710.0061.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: X-ray diffraction imaging; Raman spectroscopy; indentation geometry; plastic deformation; crack generation; plastic deformation strain imaging
Online: 10 October 2017 (11:46:27 CEST)
The crack geometry and associated strain field around Berkovich and Vickers indents on silicon have been studied by X-ray diffraction imaging and micro-Raman spectroscopy scanning. The techniques are complementary, the Raman data coming from within a few micrometers of the indentation, whereas the X-ray image probes the strain field at a distance of typically tens of micrometers. For example, Raman data provides an explanation for the central contrast feature in the X-ray images of an indent. Strain relaxation from breakout and high temperature annealing are examined and it is demonstrated that millimeter length cracks, similar to those produced by mechanical damage from misaligned handling tools, can be generated in a controlled fashion by indentation within 75 micrometers of the bevel edge of 200mm diameter wafers.
ARTICLE | doi:10.20944/preprints202309.0810.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: bicontinuous composites; carbonized leather waste; conducting polymer; globular polypyrrole; polypyrrole nanotubes; conductivity; resistivity; dye adsorption; Raman spectra
Online: 13 September 2023 (16:17:08 CEST)
Leather waste was carbonized at 800 °C in inert atmosphere. The resulting biochar was coated in situ with polypyrrole nanotubes produced by the oxidation of pyrrole in the presence of methyl orange. The composites of carbonized leather with deposited polypyrrole nanotubes of various composition were compared with similar composites based on globular polypyrrole. Their molecular structure was characterized by infrared and Raman spectra. Both conducting components formed a bicontinuous structure. The resistivity determined by four-point van der Pauw method was monitored as a function of pressure applied up to 10 MPa. The typical conductivity of composites was of the order of tenths to units S cm−1 and it was always higher for polypyrrole nanotubes than for globular polypyrrole. The conductivity decreased by 1–2 orders of magnitude after treatment with ammonia but still maintained a level acceptable for applications operating under non-acidic conditions. The composites were tested for dye adsorption, viz. cationic methylene blue and anionic methyl orange, using UV-spectroscopy. The composites are designed for the future use as functional adsorbents controlled by the electrical potential.
ARTICLE | doi:10.20944/preprints202205.0187.v1
Subject: Arts And Humanities, Art Keywords: historic pigments; colorants; nitrocellulose; X-ray radiography; X-ray fluorescence spectroscopy; infrared Fourier transform spectroscopy; Raman spectroscopy
Online: 13 May 2022 (09:44:35 CEST)
This study applied multiple scientific approaches to establish the significance of an old work of art, Red Guitar, by examining its historical origin and the color materials used in its creation. Furthremore, the study provides thus far unknown pieces of Olga Picasso's family history to be added to her biography. Scientific approaches included digital X-ray radiography, X-ray fluorescence spectroscopy, infrared Fourier transform spectroscopy, Raman spectroscopy, and elemental thermal conductivity analysis. This combination of techniques provided broad confirmation about the time when the painting was created. The work includes colors (white, black, blue, yellow, green, red, and brown/red) and prevalent use of lead-and iron-based historic pigments Chrome Yellow, Yellow Ochre and Red Ochre. It also documents the use of unconventional materials, the colorant Pigment red 4 and nitrocellulose. This investigation led to the conclusion that the art, Red Guitar, is genuine and in accord with Picasso’s work during the first two decades of the 20th century.
REVIEW | doi:10.20944/preprints202011.0312.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: Infrared spectroscopy; Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy; Raman spectroscopy; saponite, synthesis; X-ray Photoelectron Spectroscopy
Online: 10 November 2020 (13:00:59 CET)
Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4-xO10(OH,F)2.nH2O (M = interlayer cation). Both the success of the saponite synthesis and the determination of its applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponite with focus on the extensive work by one of the authors (JTK). The IR and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a possible crystallization model is provided. Infrared emission spectroscopy has been used to study the thermal changes of saponite in-situ including the dehydration and (partial) dehydroxylation up to 750˚C. 27Al and 29Si Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy is discussed (as well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray Photoelectron Spectroscopy provides besides chemical information also some information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.
ARTICLE | doi:10.20944/preprints201911.0227.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: selenite; chalcomenite; crystal structure; x-ray diffraction; raman spectroscopy; high pressure; equation of state; density functional theory
Online: 19 November 2019 (10:03:25 CET)
Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies which have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit-cell parameters as well as on the bond and polyhedral compressibility. A Birch-Murnaghan equation of state has been fitted to the unit-cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42 – 49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies is also reported.
ARTICLE | doi:10.20944/preprints202307.1314.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: novel (SiC)m/(GeC)n superlattices; interfacial layer thickness; raman intensity profiles; lattice dynamics; localization of atomic displacements
Online: 19 July 2023 (10:07:00 CEST)
Systematic results of lattice dynamical calculation are reported for the novel (SiC)m/(GeC)n superlattices (SLs) by exploiting a modified-linear chain model (M-LCM) and a realistic rigid-ion- model (RIM). By employing the bond polarizability method in the framework of M-LCM, we have simulated Raman intensities for the graded (SiC)10-D/(Si0.5Ge0.5C)D/(GeC)10-D/(Si0.5Ge0.5C)D SLs by carefully integrating interfacial layer thickness D (≡ 0, 1, 2, 3 monolayers (MLs)). The variation of D has initiated considerable up (down) shifts of GeC-, (SiC)-like Raman peaks in the middle of the optical phonon frequency region. With D = 3 MLs, the maximum energy shift (by ~ 47 cm-1) of SiC-like modes has caused substantial changes in the Raman intensity profiles linked to the localization of atomic displacements at the interfacial transition regions. This effect can be considered as a vital tool for authenticating the interfacial structures in technologically important SLs. By using a RIM, we have reported SL phonon dispersions along the growth  as well as in the plane ,  perpendicular to the growth. Our simulations of phonons in the acoustic mode region have not only confirmed the formation of minigaps at the zone center and zone edges but also provided evidence of anti-crossing and phonon confinement. Besides examining angular dependence of zone-center optical modes, we have also discussed phonon folding, confinement and anisotropic behavior in (SiC)m/(GeC)n SLs.
ARTICLE | doi:10.20944/preprints202212.0181.v1
Subject: Chemistry And Materials Science, Chemical Engineering Keywords: nanocomposites; ultralong carbon nanotubes; catalytic chemical vapor deposition; purification; catalyst removal; water vapor treatment; thermal analysis; Raman spectroscopy
Online: 9 December 2022 (13:11:58 CET)
Ultralong carbon nanotubes (UCNTs) are highly demanded for nanocomposites applications because of their magnificent physical and chemical properties. UCNTs are synthesized by catalytic chemical vapor deposition (CCVD) method and, before using as fillers in nanocomposites, should be purified from residual catalyst and non-CNT particles without significant destruction or scissoring of UCNTs. The role of water vapor for purification of UCNTs is investigated, the importance of water assistance in this process is confirmed. It was shown that wet air treatment of products of UCNTs CCVD synthesis under mild conditions can be used to decrease sufficiently residual catalyst content without significant carbon losses in comparison with the results obtained with dry air, while the residual iron content was shown to influence heavily on the subsequent oxidation of different forms of carbons, including UCNTs. The increasing of D/G ratio of Raman spectra after wet air treatment of products of UCNTs CCVD synthesis makes it possible to conclude that iron catalyst particles transform into iron oxides and hydroxides that caused inner structural strains and destruction of carbon shells improving removal of the catalyst particles by subsequent acid treatment. UCNTs purification with water assistance can be used to develop economically and ecologically friendly methods for obtaining fillers for nanocomposites of different applications.
ARTICLE | doi:10.20944/preprints202111.0078.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: GRaVN; machine learning; convolutional neural networks; CNN; raman spectroscopy; analogue missions; planetary science; random undersampling; random oversampling; CanMoon
Online: 3 November 2021 (09:24:38 CET)
During planetary exploration mission operations, one of the key responsibilities of the instrument teams to determine data viability for subsequent analysis. During the 2019 CanMoon Lunar Sample Return Analogue Mission, the Lead Raman Specialist manually examined each spectra to provide quality assurance/validation. This non-trivial process requires years of experience to complete accurately. With the proven efficacy of Convolutional Neural Networks (CNNs) in classification tasks, and the increased use of automation and control loops on planetary space platforms for navigation and science targeting, an opportunity presents itself to approach this validation problem utilising CNNs. We present the Generalised Raman Validation Network (GRaVN), an neural network focused specifically on extracting the generalised structure of Raman spectra for quality assurance/validation. This work demonstrates the viability of utilising a CNN network in validation activities for Raman spectroscopy. Utilising only two hidden layers, a configuration was developed that provided good levels of accuracy on a manually curated dataset. This indicates that such a system could be useful as part of an autonomous control loop during planetary exploration activities.
ARTICLE | doi:10.20944/preprints201807.0420.v1
Subject: Chemistry And Materials Science, Nanotechnology Keywords: layered double LDHs; graphene; mixed oxides; re-hydration; memory Effect; X-ray diffraction; Raman spectroscopy; scanning electron microscopy
Online: 23 July 2018 (12:02:37 CEST)
A graphene-containing LDH was prepared by re-hydration of the oxides produced by the calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDHs, it is unprecedented from the calcination/re-hydration of organic ones. Different temperatures (400, 600 and 1100 °C) were tested, on the basis of thermogravimetric data. Water instead of a carbonate solution was used for the re-hydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species within the layers. The samples were characterized by X-ray Powder Diffraction (XRPD), IR and Raman spectroscopy and scanning electron microscopy (SEM). XRPD indicate the presence of carbonate LDH mixed with a layered phase with a larger d-spacing. IR confirmed that the prevailing anion is carbonate, coming from the water used for the re-hydration and/or air. Raman data indicated the presence of low-ordered graphenic species moieties and SEM the absence of separated graphene of graphitic sheets, suggesting an intimate mixing of the carbonaceous phase with reconstructed LDH. Organic LDHs gave better memory effect after calcination at 400 °C. Conversely, the graphenic species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a graphene-LDH nanocomposite.
ARTICLE | doi:10.20944/preprints202104.0553.v1
Subject: Medicine And Pharmacology, Oncology And Oncogenics Keywords: Raman biosensor; Au-coated nanoparticles; hot-spot SERS substrate; anticancer drug nanocarriers; targeted drug delivery sensing; magneto-plasmonic nanoparticles.
Online: 20 April 2021 (17:43:09 CEST)
Safe administration of highly cytotoxic chemotherapeutic drugs is a challenging problem in cancer treatment due to the adverse side effects and collateral damage to non-tumorigenic cells. To mitigate these problems, new promising approaches, based on the paradigm of controlled targeted drug delivery (TDD), utilizing drug nanocarriers with biorecognition ability to selectively target neoplastic cells, are being considered in cancer therapy. Herein, we report on the design and testing of a nanoparticle-grid based biosensing platform to aid in the development of new targeted drug nanocarriers. The proposed sensor grid consists of superparamagnetic gold-coated core-shell Fe2Ni@Au nanoparticles, further functionalized with folic acid targeting ligand, model thiolated chemotherapeutic drug doxorubicin (DOX), and a biocompatibility agent, 3,6,-dioxa-octanethiol (DOOT). The employed dual transduction based on electrochemical and enhanced Raman scattering detection have enabled efficient monitoring of the drug loading onto the nanocarriers, attached to the sensor surface, as well as the drug release under simulated intracellular conditions. The grid’s nanoparticles serve here as the model nanocarriers for new TDD systems under design and optimization. The superparamagnetic properties of the Fe2Ni@Au NPs aid in nanoparticles’ handling and constructing a dense sensor grid with high plasmonic enhancement of the Raman signals due to the minimal interparticle distance.
ARTICLE | doi:10.20944/preprints202011.0579.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: heterostructures; TiO2 nanosheets; few layers MoS2/TiO2; ex-situ and in-situ approaches; FTIR; Raman; UV-Vis; XRD; HRTEM
Online: 23 November 2020 (10:17:48 CET)
MoS2/TiO2 nanostructures made of MoS2 nanoparticles covering TiO2 nanosheets have been synthesized, either via ex-situ or in-situ approaches. Morphology and structure of MoS2/TiO2 hybrid nanostructures have been investigated and imaged by means of X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM), while the vibrational and the optical properties have been investigated by Raman, Fourier-transform infrared spectroscopy (FTIR) and UV−visible (UV-Vis) techniques. The different stacking degrees together with the size distribution of the MoS2 nanosheets, decorating the TiO2 nanosheets, have been carefully obtained from HRTEM images. The nature of the surface sites on the main exposed faces of both materials has been detected by means of in-situ FTIR spectra of adsorbed CO probe molecule. The results coming from the ex-situ and in-situ approaches will be compared, by highlighting the role of the synthesis processes in affecting morphology and structure of MoS2 nanosheets, including their curvature, surface defects, and stacking order. Some more, it will be shown that the in-situ approach is affecting the reactivity of the TiO2 nanosheets too, hence in turn affects the MoS2/TiO2 nanosheets interaction.
Subject: Arts And Humanities, Archaeology Keywords: 15th-century illuminated manuscripts; smalt; bismuth ink; non-invasive analyses; Raman spectroscopy; XRF mapping; UV-vis-NIR reflectance spectroscopy
Online: 12 June 2019 (12:03:01 CEST)
This paper discusses a cross-disciplinary, international collaboration aimed at researching a series of 15th century choir books at the abbey of San Giorgio Maggiore on the homonymous island in Venice. Produced for the abbey itself, the books have never left the island during their 500-years history, thereby allowing a unique opportunity to analyse historic artefacts, which have undergone little modification over time. Prompted by ongoing cataloguing work on the manuscripts, a week-long analytical campaign using a combination of non-invasive analytical methods used in portable configuration allowed the comprehensive characterisation of ten volumes. The manuscripts’ palette and painting techniques were analysed using near-infrared imaging, reflectance spectroscopy in the UV-vis-NIR range, Raman spectroscopy, X-ray fluorescence mapping and digital microscopy. The paper will discuss the challenges linked to the fragility and the large dimensions of the volumes as well as the most interesting results of the investigation. These include the detection of unusual painting materials such as bismuth ink, as well as the discovery of a less homogeneous palette than originally expected, which prompted a partial revision of the attribution of the decoration in one of the volumes to a single artist.
ARTICLE | doi:10.20944/preprints202202.0300.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Electrochemical sensors; square-wave voltammetry; screen-printed electrodes; electrochemical profiling; illicit drugs; forensic analysis; Raman spectrometer; on-site detection; FTIR spectrometer
Online: 24 February 2022 (04:00:15 CET)
Illicit drug consumption is posing critical concerns in our society causing health issues, crime-related activities, and the disruption of border trade. The smuggling of illicit drugs urges the development of new tools for rapid on-site identification in cargos. Current methods used by law enforcement officers rely on presumptive color tests and portable spectroscopic techniques. However, these methods sometimes exhibit inaccurate results due to commonly used cutting agents, the colorful nature of the sample or because the drugs are smuggled (hidden or mixed) in common goods. Interestingly, electrochemical sensors can deal with these specific problems. Herein, an electrochemical device is presented that uses affordable screen-printed electrodes for the electrochemical profiling of illicit drugs by square-wave voltammetry (SWV). The identification of the illicit compound is based on the oxidation potential of the analyte. Hence, a library of electrochemical profiles is built upon the analysis of illicit drugs and common cutting agents. This library allows the design of a tailor-made script that enables the identification of each drug through a user-friendly interface (laptop or mobile phone). Importantly, the electrochemical test is compared by analyzing 48 confiscated samples with other portable devices based on Raman and FTIR spectroscopy as well as a laboratory standard method (i.e. gas chromatography – mass spectrometry). Overall, the electrochemical results obtained through the analysis of different samples from confiscated cargos at an end-user site, present a promising alternative to current methods, offering low-cost and rapid testing in the field.
ARTICLE | doi:10.20944/preprints202108.0362.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: silicon; nanogranular; nanoparticle; porous; void; thin film; laser heating; photo-thermal; temperature; Raman; phonons; heat conduction; phase transition; finite element modeling
Online: 17 August 2021 (10:45:12 CEST)
We present the results on photothermal (PT) and heat conductive properties of nanogranular silicon (Si) films synthesized by evaporation of colloidal droplets (drop-casting) of 100 ± 50 nm sized crystalline Si nanoparticles (NP) deposited on glass substrates. Finite difference time domain (FDTD) and finite element mesh (FEM) modeling of absorbed light intensity and photo-induced spatial temperature distribution across the Si NP films were well correlated with the local temperatures measured by micro-Raman spectroscopy and used for determination of heat conductivities in the films of various thicknesses. Cubic-to-hexagonal phase transition in these films caused by laser heating was found to be heavily influenced by the film thickness and heat conductive properties of glass substrate, on which the films were deposited. Heat conductivities across the drop-casted Si nanogranular films were found to be in the range of lowest heat conductivities of other types of nanostructurely voided Si films due to enhanced phonon scattering across inherently voided topology, weak NP-NP and NP-substrate interface bonding within nanogranular Si films.
ARTICLE | doi:10.20944/preprints202007.0274.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: tandem cells; magnetron sputtering; Raman Spectroscopy; X-Ray Diffraction; silicon deposition; Optical Transmission Spectroscopy; photocatalytic conversion; hydrogen production; post-sputtering treatments
Online: 13 July 2020 (00:33:58 CEST)
With the decline in fossil fuels, hydrogen-based alternatives provide a reliable and clean source for sustainable energy generation. In these endeavors, photochemical splitting for hydrogen production through tandem cells has been the source of much theoretical and experimental research in science. Much focus has been placed on interfacial band gap engineering as one of the most promising routes in the generation of hydrogen.This present work explores sputtering of n-silicon to form the active electrode in a n-Si | n-TiO2 tandem cell and investigates the effect of variations in sputtering and post sputtering treatment parameters (rapid thermal annealing and long cycle annealing) for successful deposition of crystalline Silicon. The samples were successfully characterized via Raman Spectroscopy, X-ray Diffraction and Optical Transmission Spectroscopy to ascertain prevalent crystalline order and optical band gap, under different sputtering and post-sputtering conditions. Relevant conclusions were drawn to ascertain the best possible deposition parameters of n-Si for photocatalytic water splitting.
ARTICLE | doi:10.20944/preprints202304.0509.v1
Subject: Physical Sciences, Optics And Photonics Keywords: synthetic diamond; ultrashort laser pulses; self-phase modulation; spontaneous Raman scattering; delayed phonon-based Kerr non-linearity; electron-phonon thermalization; phonon-phonon anharmonicity and decay
Online: 18 April 2023 (09:36:36 CEST)
In synthetic diamond plate, the intrapulse correlated dynamics of self-phase modulation and spontaneous Raman scattering by optical phonons were for the first time directly investigated for tightly focused (focusing numerical aperture NA = 0.25) positively-chirped visible-range ultrashort laser pulses with variable durations (0.3-9.5 ps) and energies, transmitted through the sample. The observed modulation of the transmitted light spectra and Stokes Raman scattering spectra for the different pulse durations were related to nonthermal excitation of nonlinear phonon polarization and its eventual picosecond-scale suppression due to thermal decay of optical phonons on the timescale of electron-phonon thermalization in the material.
ARTICLE | doi:10.20944/preprints201702.0022.v1
Subject: Physical Sciences, Optics And Photonics Keywords: Cupriavidus necator; E. coli; bofermentors; biosensors; growth phase; biosynthetic pathways; P(3HB); PHB: polyhydroxybutyrate,; spectrofluorometry; SERS: Surface Enhanced Raman Spectroscopy; turbidity as optical density (OD)
Online: 8 February 2017 (09:31:07 CET)
Polyhydroxyalcanoates (PHAs) are biodegradable polymers synthesized in cytoplasmic granules in bacteria, such as Cupriavidus necator (Ralstonia eutropha), Alcaligenes latus, Pseudomonas spp., Comamonas spp. and other species. PHAs accumulation occurs in response to stress conditions, i.e. under high carbon and low nitrogen (24:1 ratio). PHA can be synthesized using recombinant microorganisms (provided with the operon phbA/phbB/phbC), escaping the constrains of nutrient request, except addition of high amount of sugar (glucose, lactose, fructose). In this study; E. coli was genetically modified for PHB production in biofermentors. The production of PHA at industrial scale requires a continuous supplementation of fermentable sugars to support the availability of nutrients and to assess the level of the exponential growth phase; since sugars are required either for bacterial growth either for PHA synthesis and energy storage. The biofermentors need to be run in automated system. Sensors are used at many points in fermentators; in the evaluation of parameters: consumption of sugars; cell density; quantification of PHB synthesis. The need of operational control during the fermentation has prompted us to application of three measurements; one unit linked to a Nanodrop to evaluate OD; one linked to a reaction chamber to measure sugars consumed by enzyme based fluorescence detection; and one for bacteria Nile Blue staining and fluorescence intensity reads. The growth of bacteria on three different plant by-products was monitored and PHB production in four days using a banana by-product feed was optimised. These detectors will make possible to exploit the full potential of bioreactors optimizing the time of use and maximizing the number of bacteria synthesizing PHA.
ARTICLE | doi:10.20944/preprints202208.0034.v1
Subject: Physical Sciences, Applied Physics Keywords: surface-enhanced Raman scattering (SERS); silver nanoparticle (AgNP); rhodamine 6G (R6G); dc magnetron sputtering; SERS substrate; hotspot; analytical enhancement factor (AEF); limit of detection (LOD); relative standard deviation (RSD)
Online: 2 August 2022 (04:23:31 CEST)
Surface-enhanced Raman spectroscopy (SERS) is commonly used for super-selective analysis through nanostructured silver layers in the environment, food quality, biomedicine, and materials science. To fabricate a high-sensitivity but more accessible device of SERS, dc magnetron sputtering technology was used to realize high sensitivity, low cost, stable deposition rate, and rapid mass production. This study investigated various thicknesses of a silver film ranging from 3.0 to 12.1 nm by field-emission-scanning-electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. In the rhodamine 6G (R6G) testing irradiated by a He-Ne laser beam, the analytical enhancement factor (AEF) of 9.35x108, the limit of detection (LOD) of 10-8 M, and the relative standard deviation (RSD) of 1.61% were better than other SERS substrates fabricated by the same dc sputtering process because the results show that the 6 nm thickness silver layer has the highest sensitivity, stability, and lifetime. The paraquat and acetylcholine analytes were further investigated and high sensitivity was also achievable. The proposed SERS samples were evaluated and stored in a low humidity environment for up to forty weeks, and no spectrum attenuation could be detected. Soon, the proposed technology to fabricate high sensitivity, repeatability, and robust SERS substrate will be an optimized process technology in multiple applications.
ARTICLE | doi:10.20944/preprints202012.0192.v1
Subject: Physical Sciences, Optics And Photonics Keywords: nonlinear Schrödinger equation system; few-mode propagation; Kerr effect; Raman scattering; dispersion; implicit/explicit Crank–Nicolson scheme; pulse chirping, second-order dispersion, third-order dispersion, chirp pulse, optical pulse compression, pulse collapse
Online: 8 December 2020 (09:57:12 CET)
This paper discusses approaches to the numerical integration of the coupled nonlinear Schrödinger equations system in case of few-mode wave propagation. The wave propagation assumes the propagation of up to nine modes of light in an optical fiber. In this case, the light propagation is described by the non-linear coupled Schrödinger equation system, where propagation of each mode is described by own Schrödinger equation with other modes interactions. In this case, the non-linear coupled Schrödinger equation system solving becomes increasingly complex, because each mode affects the propagation of other modes. The suggested solution is based on the direct numerical integration approach, which is based on a finite-difference integration scheme. The well-known explicit finite-difference integration scheme approach fails, due to the non-stability of the computing scheme. Due to this fact, the combined explicit/implicit finite-difference integration scheme, based on the implicit Crank–Nicolson finite-difference scheme, is used. It allows ensuring the stability of the computing scheme. Moreover, this approach allows separating the whole equation system on the independent equation system for each wave mode at each integration step. Additionally, the algorithm of numerical solution refining at each step and the integration method with automatic integration step selection are used. The suggested approach has performance gains (or resolutions) up to three or more orders of magnitude in comparison with the split-step Fourier method due to the fact that there is no need to produce direct and inverse Fourier transforms at each integration step. The main advantage of the proposed method is the ability to calculate the propagation of an arbitrary number of modes in the fiber.