The ceramic sherds from approximately 20 samples of lead-glazed tableware, recovered from diverse archaeological sites, including three repurposed storage pits transformed into dumpsters within the medieval city of Santarém (13th-14th century), underwent a meticulous examination. This investigation utilized techniques such as micro-Raman, ground state diffuse reflectance absorption, and X-ray fluorescence spectroscopies, in addition to X-ray diffraction and stereomicroscopy. A parallel study was conducted on contemporaneous European ceramics (glazed sherds) sourced from archaeological sites dating back to the 13th-15th centuries in Saintonge (France), Ardenne, Zomergem, and Bruges (Belgium), as well as Surrey-Hampshire, Kingston, and Cheam (England). The colour of the ceramic bodies is predominantly white or whitish, with a few exhibiting a vivid red hue. Ceramic sherds with a light paste composition were likely crafted using kaolin clays as raw materials. Analyses of fabric, mineralogical, and elemental composition of the sherds suggest that the majority of Santarém's glazed ceramics were locally or regionally produced, potentially derived from a Pliocene kaolin-rich sand formation. However, this conclusion is not supported by the absence of discovered lead glaze kilns or workshops in Santarém for the late Middle Ages. A distinctive feature from the European workshop ceramics lies in the quartz temper content and fabric.

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.

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.

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.

The ceramic pastes of ca. 31 samples recovered from the Almaraz archaeological site, located in the south bench of Tagus River, were studied in detail using XRF, micro-Raman and GSDR spectroscopies, as well as the XRD technique. The ceramic sherds could be grouped into six categories, Red Slip tableware, Decorated tableware, Yellow Slip tableware, Grey tableware, Common tableware and Handmade pottery. Our studies of the mineralogic composition of the sherds` body indicate that all ceramics were produced locally, using silicious clays in most cases and calcareous clays in a few ones. Micro-Raman and ground state diffuse reflectance absorption spectroscopy provided useful information regarding the materials used to produce the coloured ceramics: hematite and brookite for the red slip and decorated ceramics, jacobsite or carbon black for the black decoration or grey ceramics. For the yellow slip tableware a simple engobe rich in yellow clay was used. XRF spectroscopic studies provided the elemental composition of all samples, and biplots of the Potassium (K) versus Calcium (Ca) contents, normalized to the silicon content of each ceramic paste, clearly show that Pliocene and Miocene local clays sources were used to produce most ceramics. Only one sherd can be considered a Lisbon production.

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.

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.

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.

Background. Escalating global plastic production, expected to reach 34,000 million tons by 2050, poses a significant threat to human and environmental well-being, particularly in aquatic ecosystems. Microplastics (MP) and nanoplastics (NP), which originate from the degradation of plastics, are of concern due to their potential bioaccumulation and uptake of pollutants. This study addresses identification methods and focuses on insect meal, a raw material for aquaculture feed. Methods. By using different techniques, the study was able to detect MP and NP in insect meal samples. Chemical digestion with KOH at 60°C efficiently removed organic matter without affecting the synthetic polymer polyethylene (PE). Filtration, confocal Raman microscopy, SEM and TEM were used for comprehensive analysis and integrity tests on PE films were performed using Raman and FTIR spectroscopy. The results showed the presence of PE microplastic particles in the insect meal, which was confirmed by correlative Raman and SEM mapping on a positively charged surface. In addition, the increased resolution of the Raman microscope identified submicrometric PE NP (800 nm). Transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX) confirmed plastic-like structures in the insect meal, highlighting the presence of PE plastics characterized by irregular shapes and some agglomeration. The higher carbon concentration in the EDX analysis supported the plastic nature, which was also confirmed by Raman spectroscopy. Conclusions. The study provides a robust method for the detection of MP and NP in insect meal and provides valuable insight into the possible presence of plastics in insect-based aquafeeds. The combination of different analytical methods increases the reliability of the results and sets the stage for future investigations that could focus on the quantification of NP and the assessment of their potential environmental impact.

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.

In the study, a lipid mixture was developed and optimized using a broad range of excipients of different po-larities. Initially, the excipients were classified according to their behavior in water. Then binary mixtures were prepared using cetyl palmitate (Crodamol™ CP pharma) as the solid lipid. The miscibility between the excipients was evaluated using Raman chemical images obtained by classical least squares (CLS). Based on the results, the excipients Crodamol™ CP pharma (cetyl palmitate, hydrophobic), Super Refined™ DMI (di-methyl isosorbide; hydrophilic) and Super Refined™ Lauryl Lactate (medium polarity) were chosen to com-pose the lipid core. The ideal proportion of these excipients was determined using a Mixture Design and the standard deviation of image histograms as responses. The main goal was to develop a versatile lipid core for ‘brick-dust type of drugs’. After statistical evaluation of the DOE results, the final composition was deter-mined and drugs with different logP (0 to 10) and physiochemical characteristics were evaluated in the opti-mized mixture. The drugs butamben, tacrolimus, atorvastatin calcium and resveratrol presented a homoge-neous distribution in the optimized lipid core, indicating that the core has indeed the capability to be used in NLC formulations of such type of drugs.

The thermal decomposition of siderite and its decomposition products in a vacuum atmosphere was investigated for the first time using in situ high-temperature transmission Mössbauer spectroscopy. These measurements were supported by X-ray diffraction, Raman spectroscopy, X-ray fluorescence, and magnetic measurements. In situ Mössbauer spectra were collected from room temperature (RT) to 750 oC with a temperature step of 50 oC. After that, the sample was cooled down to RT with step 100 oC. Raw siderite samples contain siderite as the only iron-bearing mineral, and after heating the samples at high temperatures, hematite and magnetite are only Fe-bearing phases. In the temperature range of 300 oC - 500 oC, siderite decomposition occurs. The analysis shows that siderite transforms directly into magnetite, and then hematite generation occurs as long as siderite is present in the sample. Changing hyperfine parameters like isomer shift, quadrupole splitting, or hyperfine magnetic field versus temperature were obtained for siderite and iron oxides (hematite, magnetite). The measurements also show that magnetite formed during the decomposition of siderite is a composition of particles of various sizes and a low degree of crystallization.

This research aims to deepen the understanding of the relationship between conductivity and morphology in polypyrrole (PPy) via a comparison of the bipolaron to polaron ratios with a focus on the C-H deformation area. PPy samples were synthesized with different surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and tween 80 (TW). The study revealed that SDS significantly altered the bipolaron and polaron in C-H deformation region and showed higher conductivity than other surfactants. Notably, the morphological shifts to a sheet-like structure when using ammonium sulfate (APS) contrasted with the particle-like form observed with ferric chloride (FeCl3). These results showed that if the oxidant changed, the bi-polaron and polaron ratios in C-H deformation were unrelated to PPy morphology. However, this work showed a consistent relationship between SDS use, the bipolaron and polaron ratios in the C-H deformation, and the conductivity properties. Moreover, the natural positive charge of PPy and negatively charged SDS molecules may lead to an electrostatic interaction between PPy and SDS. This work assumes that this interaction might cause the transformation of polaron to bipolaron in the C-H deformation region, resulting in improved conductivity of PPy. This work offers more support for the future investigation of PPy characteristics.

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.

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.

Nonlinear compression of narrow-band (Δ ≈ 0.2 cm-1) 20 ns KrF laser pulses in SF6 at 10 atm and CH4 at 50 atm pressure was studied. Both SBS and SRS optically phase conjugated backward reflected radiation was registered with energy reflectivity 10−14% in SF6 and CH4. In SF6 SBS pulses gradually shortened from 10 ns to 2−3 ns with pumping decrease to the SBS threshold ~ 10 mJ, while the SRS pulse had the shortest length of 30−60 ps for the maximal pumping of 120 mJ and broadened near the SRS threshold of ~30 mJ. For the SRS pulse energy ~ 2 mJ peak power 5×107 W was tenfold higher than the pump power. The theoretical model predicted a soliton-like SRS pulse compression to a temporal length of the order of vibrational relaxation time. There was no pulse compression of backward SBS and SRS radiation in CH4, while in the forward direction SRS pulses shortened to 3−4 ns at reduced pumping.

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.

The fixation and activation of the dinitrogen molecule, N2 by hexametallic clusters of the general formula {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 (L = CH2-, NH2-, PH2-, OH-, SH-, BH2- and NH2-, M = Ru(II) or Os(II)) were scrutinized by means of density functional theory calculations. In these systems, the dinitrogen molecule, acts as a ligand that bridges the two opposite facing triangular metallic rings, cyclo-M3 of the {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 clusters The hexametallic clusters, that mimick the six Fe cluster of nitrogenase, were found to strongly activate N2, converting it into a hydrazido-like group, N24-. This is substantiated by the calculated N-N bond lengths, Re(N-N) and the stretching frequencies of the N-N bond of dinitrogen, vs(N-N) found in the ranges 1.299 – 1.487 Å and 780 – 1270 cm-1 respectively. Based on the Re(N-N) and vs(N-N) values, the dinitrogen activation depends upon the nature of the hexametallic cluster. Accordingly, the Os(II) clusters were found to activate more strongly the dinitrogen molecule as compared to their Ru(II) counterparts. The nature of the ligand L also affects the extent of the N2 activation by the hexametallic clusters, which follows the order BH2- < NH2- < OH- < CH2- < NH2- < PH2-, SH- for M = Ru(II) and the order BH2- < NH2- < OH- < NH2- < CH2- < PH2- < SH- for M = Os(II). Thus, the strongest N2 activation is observed for the {[(μ2-SH)Os)]6(μ-η1:η3-Ν2)}+6 cluster and the weakest for the {[(μ2-BH)Ru)]6(μ-η1:η3-Ν2)}0 cluster. The calculated Nitrogen-15 NMR isotropic chemical shielding tensors, σiso(15N) exhibit shielding (upfield) upon N2 fixation to the metal centers of the hexametallic clusters, as a results of electron density transfer towards its constituent N nuclei. A multitude of electronic charge distribution partitioning schemes were applied to assist in delineating the bonding properties of the {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 clusters. Accordingly, it is found that there is a donation/backdonation interaction between the bridging N2 ligand and the two opposing cyclo-M3 rings located on either side. The dinitrogen ligand forms six bonds of mixed covalent/electrostatic nature with the six metal centers of the {[(μ2-L)M)]6)}0/+6 clusters.

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.

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 [001] as well as in the plane [100], [110] 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.

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.

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.

Fused deposition modeling (FDM) is a rather new technology in the production of personalized dosage forms. Melting and printing of polymer–active pharmaceutical ingredient (API) – mixtures can be used to produce oral dosage forms with different dosage as well as release behavior. This process is utilized to increase the bioavailability of pharmaceutically relevant active ingredients that are poorly soluble in physiological medium by transforming them into solid amorphous dispersions (ASD). Release from such ASDs is expected to be faster and higher compared to the raw materials and thus enhance bioavailability. Printing directly from powder while forming ASDs was realized. Different techniques to change release patterns as well as a non-destructive way for determination of API distribution were shown. By measuring the melt viscosities of mixtures printed a rheological model for the printer used is proposed.

This study introduces a compact Raman spectrometer with a 1064 nm excitation laser coupled with a fiber probe and an inexpensive motorized stage, offering a promising alternative to widely used Raman imaging instruments with 785 nm excitation lasers. The benefits of 1064 nm excitation for biomedical applications include further suppression of fluorescence background and deeper tissue penetration. The performance of the 1064 nm instrument in detecting cancer in human bladder resectates is demonstrated. Raman images with 1064 nm excitation were collected ex vivo from 10 human tumor and non-tumor bladder specimens and the results are compared to previously published Raman images with 785 nm excitation. K-Means cluster (KMC) analysis is used after pre-processing to identify Raman signatures of control, tumor, necrosis, and lipid-rich tissues. Hierarchical cluster analysis (HCA) groups the KMC centroids of all specimens as input. The tools for data processing and hyperspectral analysis were compiled in an open source Python library called SpectraMap (SpMap). In conclusion, the 1064 nm Raman system can differentiate between tumor and non-tumor bladder tissues in a similar way to 785 nm Raman spectroscopy. These findings hold promise for future clinical hyperspectral imaging.

Raman spectra of [TeX6](Y2) (X, Y - Cl, Br, I) were recorded in the temperature range 5-300 K. The vibration frequency of molecular halogens as function on temperature and the type of halogen X- in the [TeX6]2- complex was obtained. The vibration frequency of the molecular halogen Y2 depends on the type of halogen X- complex [TeX6]2- The temperature dependence of the Y2 frequency is anomalous compared to what was expected for a conventional anharmonic oscillator. It is shown that the interpretation of the experimental results based on the concept of traditional chemical bonding is quite satisfactory in all cases. The study was motivated by the need to consider the mechanism of interaction in the X-Y2 contacts.

The conformations of trifluoroacetyl triflate, CF3C(O)OSO2CF3, were investigated through vibrational experimental methods (gas-phase FTIR, liquid-phase Raman, and Ar-matrix FTIR spectroscopy) and Density Functional Theory (DFT) calculations. A potential energy surface was computed using the B3P86 /6-31+g(d) approximation as a function of the dihedral angles τ1 = CCOS and τ2 = COSC. The surface reveals three minima, which were further optimized using the B3LYP method with various basis sets (6-31++G(d), 6-311++G(d), tzvp and cc-pvtz). The global minimum corresponds to a syn-anti conformer (the CO double bound syn with respect the O−S single bond and the C−O single bond anti with respect to de S−C single bond). The other two minima represent enantiomeric syn-gauche forms. The Ar-matrix FTIR spectrum exhibited clear evidence of the presence of two conformers. Furthermore, the randomization process observed following broad-band UV-visible irradiation facilitated the identification of the IR absorption of each conformer. Based on the Ar-matrix FTIR experiments, the vapour phase of trifluoroacetyl triflate at room temperatures was composed of approximately 60-70% of the syn-anti conformer and 30-40% of the syn-gauche form.

Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium Nitride-based devices, specifically AlGaN/GaN High Electron Mobility Transistors (HEMTs) in a novel packaging design provided by STMicroelectronics S.r.l. The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of a packaging.