ARTICLE | doi:10.20944/preprints201703.0056.v1
Subject: Chemistry, Other Keywords: Ag/MgAl2O4; characterization; activity; Photocatalytic degradation; Methylene blue
Online: 10 March 2017 (10:37:46 CET)
In the present work report, the MgAl2O4and the Ag/MgAl2O4 samples were successfully synthesized by the modified hydrothermal and the isovolumetric impregnation methods, respectively. The structural properties of the prepared samples were systematically characterized by XRD, SEM, TEM, DRS, XPS and et al techniques. The photocatalytic degradation of methylene blue by the Ag/MgAl2O4 and MgAl2O4 samples was comparatively studied under UV lamp irradiation. The results revealed that the prepared Ag/MgAl2O4 (pH=6) samples were the most active among the samples in photocatalytic of methylene blue. Under UV lamp irradiation, the Ag/MgAl2O4 (pH=6) photodegradation of methylene blue reached to 89.6% within 120 min. And the Ag/MgAl2O4 (pH=6) complex photocatalysts displayed a high photochemical stability under repeated irradiation. Repeated irradiate the Ag/MgAl2O4 (pH=6) compound, which indicated it had a high photochemical stability.
ARTICLE | doi:10.20944/preprints201905.0375.v1
Subject: Materials Science, Nanotechnology Keywords: Liquid phase transformation; Ag flakes; Ag meshes, elastic electrodes
Online: 31 May 2019 (08:20:04 CEST)
Flexible and stretchable conductive materials have received significant attention in several applications such as flexible displays and sensors. In this paper, we report a highly dispersed porous Ag nanoflakes with clean surfaces were fabricated through an explosive growth process. The evolution process from silver nanoflakes to nanomeshes occurred by the novel “dissolution–recrystallization” solvothermal process. The as-obtained Ag meshes have the dual nature of nanoflakes and nanoparticles, which could create an intercross and interpenetration conductive network structures between silver and polymer in the printed elastic conductor, therefore, the silver meshes as conductive fillers used in elastic conductor simultaneously exhibit high conductivity and mechanical durability.
ARTICLE | doi:10.20944/preprints202105.0562.v1
Subject: Materials Science, Biomaterials Keywords: MgAl2O4, Single atomic Nin+, RWGS, Stability, Reaction mechanism
Online: 24 May 2021 (10:50:17 CEST)
Reverse water gas shift reaction (RWGS) is an important process which plays a vital role in many CO2 utilization related reactions. Noble metals are the most active catalysts in RWGS, but the high price and low reserve strangled their applications. In the present work, we reported a non-transition-metal MgAl2O4 catalyst which showed outstanding activity and stability at high temperatures in the RWGS reaction and improved performance after doping of single atomic Nin+. The catalyst can obtain 46% of CO2 conversion in durability test of 75 h at 800 °C under high weight hourly space velocities (225 000 ml g-1 h-1). The adsorption sites, possible reaction route, and effects of Nin+ single atoms on the (111) surface of MgAl2O4 for RWGS were investigated by in situ DRIFTS and DFT calculations. The results indicated that the rate determining reaction step of RWGS on MgAl2O4 and Ni (SA)/MgAl2O4 were both the reaction of OH* + H* → H2O* + *, but the energy barrier was significantly reduced after introducing single atomic Nin+. Nin+ atoms can increase the hydroxyl coverage on the surface of catalyst and Al3+ sites near the Nin+ ion are considered as the predominant active sites for RWGS reactions.
ARTICLE | doi:10.20944/preprints202011.0316.v1
Subject: Materials Science, Biomaterials Keywords: Hydrogen production; Methane cracking; DBD plasma reactor; MgAl2O4; CNTs
Online: 10 November 2020 (13:51:09 CET)
The study experimentally investigated a novel approach for producing hydrogen from methane cracking in dielectric barrier discharge catalytic plasma reactor using a nanocatalyst. Plasma-catalytic methane (CH4) cracking was undertaken in a dielectric barrier discharge (DBD) catalytic plasma reactor using Ni/MgAl2O4. The Ni/MgAl2O4 was synthesised through co-precipitation followed customised hydrothermal method. The physicochemical properties of the catalyst were examined using X-ray diffraction (XRD), scanning electron microscopy - energy dispersive X-ray spectrometry (SEM-EDX) and thermogravimetric analysis (TGA). The Ni/MgAl2O4 shows a porous structure spinel MgAl2O4 and thermal stability. In the catalytic-plasma methane cracking, the Ni/MgAl2O4 shows 80% of the maximum conversion of CH4 with H2 selectivity 75%. Furthermore, the stability of the catalyst was encouraging 16 hours with CH4 conversion above 75%, and the selectivity of H2 was above 70%. This is attributed to the synergistic effect of the catalyst and plasma. The plasma-catalytic CH4 cracking is a promising technology for the simultaneous H2 and carbon nanotubes (CNTs) production for energy storage applications.
ARTICLE | doi:10.20944/preprints202002.0287.v1
Subject: Materials Science, Biomaterials Keywords: Ag; Colletotrichum gloeosporioides; laser; dewetting
Online: 20 February 2020 (06:53:09 CET)
Silver particles are prepared by dewetting Ag ﬁlms coated on glass using a fiber laser. The size of the particles is controlled in the range of 92 nm ~ 1.2 μm by adjusting the thickness of the Ag film. The structural properties and surface roughness of the particles are evaluated by means of scanning electron microscopy. In addition, the antifungal activity of the Ag particles is examined using spore suspensions of Colletotrichum gloeosporioides. It is shown that the particles with a size of 1.2 μm achieve 100% inhibition of the conidia growth of the Colletotrichum gloeosporioides after a contact time of just 5 min. Furthermore, the smaller particles also achieve a good antibacterial activity given a longer contact time. Similar results are observed in spore germination and pathogenicity tests performed on mango fruit and leaves. Overall, the results confirm that the Ag particles have an excellent antifungal effect on Colletotrichum gloeosporioides.
ARTICLE | doi:10.20944/preprints202001.0348.v1
Online: 29 January 2020 (04:35:25 CET)
PEBAX-2533/metal salt/Al salt membranes were prepared for mixed olefin/paraffin separation. PEBAX-2533 with 80% ether group and 20% amide group was suggested as the polymer matrix for comparison of separation performance according to the functional group ratio in copolymer PEBAX. In addition, Al salts were used to stabilize metal ions for a long time as additives. High permeance was expected with the proportion of high ether groups since these functional groups provided relatively permeable regions. As a result, the PEBAX-2533 composite membrane showed a selectivity of 5 (propylene/propane) with 10 GPU. However, the permeance of membrane was not unexpectedly improved and the selectivity was reduced. The result was analyzed by SEM, FT-RAMAN and TGA, including FT-IR. The reduction in separation performance was determined by FT-IR. From these results, in order to stabilize the metal ions interacting with the polymer through Al(NO3)3, it was concluded that specific ratio of amide group was needed in PEBAX as polymer matrix.
ARTICLE | doi:10.20944/preprints201904.0136.v1
Online: 11 April 2019 (08:52:43 CEST)
Abstract: Microstructural and mechanical properties of the eutectic Sn58Bi and micro-alloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag micro-alloy, the tensile strength was improved and this is attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility is slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag micro-alloyed Sn58Bi solder joints produced utilising a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results reveal that micro-alloyed Sn57.6Bi0.4Ag has a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn-Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.
ARTICLE | doi:10.20944/preprints202105.0715.v1
Subject: Materials Science, Nanotechnology Keywords: colloidal nanocrystals; Ag2ZnSnS4; phonons; Ag-Zn-S; Ag-Sn-S; non-stoichiometry; secondary phase; XPS; FTIR
Online: 31 May 2021 (08:33:21 CEST)
The variation of the cationic composition in I2-II-IV-VI4 semiconductor compounds is an effective tool for altering their properties in a controlled manner. In particular, a partial substitution of Cu for Ag in kesterite Cu2ZnSnS4 was proposed to suppress Cu-Zn antisite defects and the improve photovoltaic performance. However, the efficiency of this approach may substantially depend on the fabrication route. Here, we report on the synthesis of (Cu,Ag)-Zn-Sn-S (CAZTS) and Ag-Zn-Sn-S (AZTS) nanocrystals (NCs) by means of "green" chemistry in aqueous solution and their detailed characterization by Raman spectroscopy and by several complementary techniques. Through a systematic variation of the nominal composition and quantification of the constituent elements in CAZTS and AZTS NCs by XPS, we identified the vibrational Raman and IR fingerprints of both the main AZTS phase and secondary phases of Ag-Zn-S and Ag-Sn-S compounds (for the first time). The formation of the secondary phases of Ag-S and Ag-Zn-S cannot be avoided entirely for this type of synthesis. The Ag-Zn-S phase, having its bandgap in near infrared range, is the reason of the non-monotonous dependence of the absorption edge of CAZTS NCs on the Ag content, with a trend to redshift even below the bandgaps of bulk AZTS and CZTS.
ARTICLE | doi:10.20944/preprints201804.0277.v1
Subject: Earth Sciences, Geochemistry & 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/preprints202010.0104.v1
Online: 5 October 2020 (17:51:13 CEST)
In this research, first a binary nanocomposite of magnetic recyclable photocatalyst Fe3O4/TiO2, was synthesized by sol gel technique. Then, in order to enhance the photocatalytic activity of the synthesized nanocomposite, it was deposited by silver nanoparticles for using in degradation of organic pollutants 2, 4-dichlorophenol (2, 4-DCP) under visible light. A range of analytical techniques including XRD, FESEM/EDX, DRS, VSM and N2 physisorption were employed to reveal the crystal structure, morphology and property of the nanocomposites. We obtained 32% and 55% degradation of 2, 4-DCP under visible light after 180 min irradiation in the presence of Fe3O4/TiO2 and Fe3O4/TiO2/Ag respectively. Thus, the excellent visible light photocatalytic activity of Fe3O4/TiO2/Ag sample can be attributed to the surface plasmon resonance effect of Ag nanoparticles deposited on Fe3O4/TiO2 nanocomposite.
ARTICLE | doi:10.20944/preprints201711.0004.v1
Subject: Materials Science, General Materials Science Keywords: rotating photocatalytic reactor; TiO2 /Ag catalysts; water treatment
Online: 1 November 2017 (04:44:39 CET)
A four stage semi-pilot scale RFR reactor with ceramic disks as support for TiO2 modified with silver particles was developed for the removal of organic pollutants. The design presented in this article is an adaptation of the rotating biological reactors (RBR) and its coupling with the modified catalyst provides additional advantages to designs where a catalyst in suspension is used. The optimal parameter of rotation was 54 rpm and the submerged surface of the disks offer a total contact area of 387 M2. The modified solid showed a decrease in the value of its bandgap compared to commercial titanium. The system has a semi-automatic operation with a maximum reaction time of 50 h. Photo-activity tests show high conversion rates at low concentrations. The results conform to the Langmuir heterogeneous catalysis model.
REVIEW | doi:10.20944/preprints201703.0072.v1
Subject: Materials Science, Biomaterials Keywords: micro-arc oxidation; antibacterial ability; Ag; Cu; Zn
Online: 14 March 2017 (07:49:40 CET)
Ti and its alloys are the most commonly used materials for biomedical applications. However, bacterial infection after implant placement is still one of the significant rising complications. Therefore, the application of the antimicrobial agents into implant surfaces to prevent implant-associated infection has attracted lots of attention. Scientific papers have shown that inorganic antibacterial metal element (e.g. Ag, Cu, Zn) can be introduced to implant surfaces with the addition of metal nanoparticles or metallic compounds into electrolyte via micro-arc oxidation (MAO) technology. In this review, the effects of the composition and concentration of electrolyte and process parameters (e.g. voltage, current density, oxidation time) on morphological characteristics (e.g. surface morphology, bonding strength), antibacterial ability and biocompatibility of MAO antimicrobial coating were discussed in detail. Anti-infection and osseo-integration can be simultaneously accomplished with the selection of the proper antibacterial elements and operating parameters. Besides, MAO assisted by magnetron sputtering (MS) to endow Ti-based implant materials with superior antibacterial ability and biocompatibility was also discussed. Finally, the development trend of MAO technology in the future was forecasted.
ARTICLE | doi:10.20944/preprints202104.0319.v1
Subject: Earth Sciences, Atmospheric Science Keywords: olivine aggregates; CO2; crystallographic preferred orientation; AG-type fabric
Online: 12 April 2021 (14:28:27 CEST)
Shear deformation of a solid-fluid, two-phase material induces a fluid segregation process that produces fluid-enriched bands and fluid-depleted regions, and crystallographic preferred orientation (CPO) characterized by girdles of  and  axes sub-parallel to the shear plane and a cluster of  axes sub-normal to the shear plane, namely the AG-type fabric. Based on experiments of two-phase aggregates of olivine + basalt, a two-phase flow theory and a CPO-formation model were established to explain these microstructures. Here, we investigate the microstructure in a two-phase aggregate with supercritical CO2 as the fluid phase and examine the theory and model, as CO2 is different from basaltic melt in rheological properties. We conducted high‐temperature and high-pressure shear deformed experiments at 1 GPa and 1100ºC in a Griggs-type apparatus on samples made of olivine + dolomite, which decomposed into carbonate melt and CO2 at experimental conditions. After deformation, CO2 segregation and an AG-type fabric occurred in these CO2-bearing samples, inconsistency with basaltic melt-bearing samples. The SPO-induce CPO model was used to explain the formation of the fabric. Our results suggest that the influences of CO2 as a fluid phase on the microstructure of a two-phase olivine aggregate is similar to that of basaltic melt and can be explained by the CPO-formation model for the solid-fluid system.
REVIEW | doi:10.20944/preprints202102.0030.v1
Subject: Biology, Anatomy & Morphology Keywords: AEA; 2-AG; CB1; CB2; endocannabinoid; regeneration; neurodevelopment; invertebrate
Online: 1 February 2021 (13:16:51 CET)
Cannabis has long been used for its medicinal and psychoactive properties. With the relatively new adoption of formal medicinal cannabis regulations worldwide, the study of cannabinoids, both endogenous and exogenous, has similarly flourished in more recent decades. In particular, research investigating the role of cannabinoids in regeneration and neurodevelopment has yielded promising results in vertebrate models. However, regeneration-competent vertebrates are few, whereas a myriad of invertebrate species have been established as superb models for regeneration. As such, this review aims to provide a comprehensive summary of the endocannabinoid system, with a focus on current advances in the area of endocannabinoid system contributions to invertebrate neurodevelopment and regeneration.
ARTICLE | doi:10.20944/preprints202010.0103.v1
Online: 5 October 2020 (17:49:27 CEST)
In this work, pure TiO2 and binary nanocomposites of Fe3O4/TiO2 and Ag/TiO2 were synthesized in order to improve photocatalytic performance of these samples for degradation of 2, 4-dichlorophenol (2, 4-DCP) as an organic pollutant. A range of analytical techniques including XRD, DRS, SEM/EDX, and elemental mapping were employed to reveal the crystal structure, morphology and property of the nanocomposites. XRD data demonstrated that the prepared samples are purely in TiO2 anatase phase and cubic spinel Fe3O4 exist in the synthesized nanocomposite. We calculated the TiO2 crystal size from XRD patterns, in the range of 8.35-11.09 nm. The presence of Ag, Fe, O, and Ti atoms in the synthesized nanocomposites was confirmed by SEM/EDX. We obtained 30.43, 32.02 and 42.40 % degradation of 2, 4-DCP (100 ml 2, 4-DCP 40 ppm and 0.01 g catalyst) for pure TiO2, Fe3O4/TiO2 and Ag/TiO2, respectively, after 180 min of irradiation under visible light. Similar conditions were employed for 2, 4-DCP degradation under UV irradiation, we obtained 53.05, 51.00 and 71.50 % degradation of 2, 4-DCP pure TiO2, Fe3O4/TiO2 and Ag/TiO2, respectively. Thus, the synthesized binary nanocomposites exhibited higher photocatalytic activity compared to pure TiO2 under visible light.
Subject: Materials Science, Biomaterials Keywords: Photocatalytic materials; Ag nanowire; Surface plasmon resonance; Nanocomposite; Rhodamine B
Online: 4 January 2021 (12:44:05 CET)
This paper investigates the photocatalytic characteristics of Ag Nanowire (AgNW)/TiO2 and AgNW/TiO2/Graphene oxide (GO) nanocomposites. Samples were synthesized by the direct coating of TiO2 particles on the surface of silver nanowires. As-prepared AgNW/TiO2 and AgNW/TiO2/GO nanocomposites were characterized by electron microscopy, X-ray diffraction, UV/visible absorption spectroscopy, and infrared spectroscopy. Transmission electron microscope (TEM) images confirmed the successful deposition of TiO2 nanoparticles on the surface of AgNWs. The photocatalytic activity of synthesized nanocomposites was evaluated using Rhodamine B (RhB) in an aqueous solution as the model organic dye. Results showed that synthesized AgNW/TiO2/GO nanocomposite has superior photocatalytic activities when it comes to the decomposition of RhB.
Subject: Chemistry, Chemical Engineering Keywords: polyethylene; nanocomposites; silver nanoparticles; Fe3O4-Ag hybrid nanoparticles; antibacterial activity
Online: 19 March 2019 (07:54:54 CET)
We report here the synthesis of uniform nanospheres-like silver nanoparticles (AgNPs, 5-10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAgNPs, 8-16 nm) by the use of seeding growth method in the presence of oleic acid (OA)/oleylamine (OLA) as surfactants. The antibacterial activity of pure nanoparticles and nanocomposites by monitoring the bacterial lag–log growth has been investigated. The electron transfer from AgNPs to Fe3O4NPs which enhances the biological of silver nanoparticles has been proven by nanoscale Raman spectroscopy. The lamellae structure in the spherulite of FeAgNPs/PE nanocomposites seems play the key role to the antibacterial activity of nanocomposites, which has been proven by nanoscale AFM-IR. An atomic force microscopy coupled with nanoscale infrared microscopy (AFM-IR) is use to highlight the distribution of nanoparticles on the surface of nanocomposite at the nanoscale. The presence of FeAgNPs in PE nanocomposites has a better antibacterial activity than that reinforced by AgNPs due to the faster Ag+ release rate from the Fe3O4-Ag hybrid nanoparticles and the ionization of AgNPs in hybrid nanostructure.
BRIEF REPORT | doi:10.20944/preprints202103.0246.v1
Subject: Engineering, Automotive Engineering Keywords: Digital microfluidics; PMMA; Kapton; Ag ink; Silver nanoparticles; Inkjet printed electrodes
Online: 9 March 2021 (09:30:33 CET)
Digital microfluidics (DMF) devices enable precise manipulation of small liquid volumes in point-of-care testing. Printed circuit board (PCB) substrate is commonly utilized to build DMF devices. However, inkjet printing can be used to fabricate DMF circuits, providing a less expensive alternative to PCB-based DMF designs while enabling more rapid design iteration cycles. We demonstrate the fabrication process of the inkjet-printed DMF circuit. We compare Kapton and polymethyl methacrylate (PMMA) as dielectric coatings by measuring the minimal droplet actuation voltage for a range of actuation frequencies. The minimum actuation voltage of 5.6 V was required for droplet movement with the PMMA layer thickness of 0.2 μm and a hydrophobic layer of 0.17 μm. Significant issues with PMMA dielectric breakdown were observed at actuation voltages above 10 V. In comparison, devices that utilized Kapton were found to be more robust even at the actuation voltage up to 100 V.
ARTICLE | doi:10.20944/preprints202102.0428.v1
Subject: Materials Science, Biomaterials Keywords: Ag nanoparticle; localized surface plasmon resonance; color; red-shift; blue-shift
Online: 19 February 2021 (09:52:47 CET)
Fresh Ag nanoparticles (NPs) dispersed on a transparent SiO2 exhibit an intense optical extinction band originating in localized surface plasmon resonance (LSPR) in visible range. The intensity of LSPR band weakened when the Ag NPs was stored in ambient air for two weeks. The rate of the weakening and the LSPR wavelength shift, corresponding to visual chromatic changes, strongly depended on the environment in which Ag NPs were set. The origin of a chromatic change was discussed along with both compositional and morphological changes. In one case, bluish coloring followed by a prompt discoloring was observed for Ag NPs placed near the ventilation fan in our laboratory, resulted from adsorption of large amounts of S and Cl on Ag NP surfaces as well as particle coarsening. Such color changes deduce the presence of significant amounts of S and Cl in the environment. In other case, a remarkably blue-shift of LSPR band was observed for the Ag NPs stored in the desiccator made of stainless steel, originated in the formation of CN and/or HCN compounds and surface roughening. Their color changed from maroon to reddish, suggesting that such molecules were present inside the desiccator.
ARTICLE | doi:10.20944/preprints202012.0686.v1
Subject: Medicine & Pharmacology, Allergology Keywords: malignant neoplasia; transoral reconstruction; polydimethyl siloxane; Ag nanoparticles; fatigue strenght; prosthesis
Online: 28 December 2020 (11:24:53 CET)
This study aims to establish whether the use of biomaterials, particularly polydimethylsiloxane (PDMS), for surgical reconstruction of the esophagus with templates, Montgomery salivary tube, after radical oncology surgery for malignant neoplasia is an optimal choice for patients’ safety and for optimal function preservation and organ rehabilitation. Methods: Structural analysis by Raman spectrometry and biomechanical properties with dynamic mechanical analysis are performed for fatigue strength and toughness, essential factors in durability of a prosthesis in the reconstruction practice of the esophagus. Nanocomposites with silicone elastomers and nanoparticles used in implantable devices and in the reconstruction surgery are facing risks of infection and fatigue strength when required to perform a mechanical effort for long periods of time. Results: This report takes into account the effect of silver (Ag) nanoparticles on the fatigue strength using polydimethylsiloxane (PDMS) matrix, representative for silicon elastomers used in implantable devices. PDMS with 5% (wt) Ag nanoparticles of 100-150 nm during mechanical fatigue testing at shear strength loses elasticity properties after 400 loading-unloading cycles and up to 15% shear strain. The fatigue strength, toughness, maximum shear strength are the key issues in designing Montgomery salivary tube with appropriate biomechanical behavior for each patient. Conclusions: Prosthesis design needs to indulge both clinical outcome as well as design methods and research in the field of biomaterials.
ARTICLE | doi:10.20944/preprints201702.0013.v1
Subject: Materials Science, Nanotechnology Keywords: nano-cube; heterostructures; bottom-up growth; electron microscopy; bandgap; Ag-WO3
Online: 4 February 2017 (09:23:00 CET)
A new class of nano-cube core-shell heterostructures containing Ag coating on the top of WO3 was fabricated. Physical vapor deposition was used to produce WO3 based nano-heterostructures. All kind of wet toxic chemical process was avoided to make the process simple and contaminant free. Sputtering of WO3 and a subsequent thermal annealing process was done to create nano-cubes of WO3. After that, sputtering of Ag was performed to form the Ag-WO3 core-shell nano-heterostructures (CSNH). The CSNHs were characterized using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and UV-vis spectroscopy. The morphologies, elemental analysis, interfaces, crystallinity, phases, and chemical compositions were analyzed. The bottom-up growth of WO3 nanocubes was studied using different time periods at 900°C. Ag coating was also studied before and after annealing. Finally, an optical property (band gap) was also analyzed using Tauc plot derive from absorption spectra. The tailoring the band gap of WO3 from ~2.9eV to ~ 2.45 eV was observed while Ag-WO3 CSNH formed.
ARTICLE | doi:10.20944/preprints202101.0256.v1
Subject: Materials Science, Biomaterials Keywords: Ti-Cu-Ag thin films; Mechanical properties; Magnetron sputtering; Nanoindentation; FIB-DIC
Online: 13 January 2021 (15:11:02 CET)
In this work, the ternary titanium, copper and silver (Ti-Cu-Ag) system is investigated as a potential candidate for the production of mechanically robust biomedical thin films. The coatings are produced by physical vapor deposition-magnetron sputtering (MS-PVD). The composite thin films are deposited on a silicon (100) substrate. The ratio between Ti and Cu was approximately kept one, with the variation of the Ag content between 10 and 35 at.%, while the power on the targets is changed during each deposition to get the desired Ag content. Thin film characterization is performed by x-ray diffraction (XRD), nanoindentation (modulus and hardness) and Atomic force microscopy to determine the surface topography. The residual stresses are measured by focused ion beam and digital image correlation method (FIB-DIC). The produced Ti-Cu-Ag thin films appear to be smooth, uniformly thick and exhibit amorphous structure for the Ag contents lower than 25 at.%, with a transition to partially crystalline structure for higher Ag concentrations. The Ti-Cu control film shows higher values of 124.5 GPa and 7.85 GPa for modulus and hardness respectively. There is a clear trend of continuous decrease in the modulus and hardness with the increase of Ag content, as lowest value of 105.5 GPa and 6 GPa for 35 at.% Ag containing thin films. In particular, a transition from the compressive (-36.5 MPa) to tensile residual stresses between 229 MPa and 288 MPa are observed with an increasing Ag content. The obtained results suggest that the Ag concentration should not exceed 25 at.%, in order to avoid an excessive reduction of the modulus and hardness with maintaining (at the same time) the potential for an increase of the antibacterial properties. In summary, Ti-Cu-Ag thin films shows characteristic mechanical properties that can be used to improve the properties of biomedical implants such as Ti-alloys and stainless steel.
ARTICLE | doi:10.20944/preprints201703.0201.v1
Subject: Materials Science, General Materials Science Keywords: mesoporous TiO2; reduced graphene oxide; Ag nanoparticles; photocatalytic activity; visible light irradiation
Online: 27 March 2017 (12:01:25 CEST)
Mesoporous TiO2/reduced graphene oxide/Ag (TiO2/RGO/Ag) ternary nanocomposite with effective electrons transfer pathway is obtained by an electrostatic self-assembly method and photo-assisted treatment. Compared with bare mesoporous TiO2 (MT) and mesoporous TiO2/RGO (MTG), the ternary mesoporous TiO2/RGO/Ag (MTGA) nanocomposite exhibited superior photocatalytic performance for the degradation of MB under visible light, and the degradation rate reached 0.017 min-1, which was 3.4 times higher than that of MTG. It is proposed that Ag nanoparticles can form the local surface plasmon resonance (LSPR) to absorb the visible light and distract the electrons into MT, and RGO can accept the electrons from MT to accelerate the separation efficiency of carriers. The establishment of MTGA ternary nanocomposite make the three components act synergistic effect to enhance the photocatalytic performance.
ARTICLE | doi:10.20944/preprints201807.0197.v1
Subject: Biology, Physiology Keywords: Cannabis, obesity, body mass index, CB1R, AEA, 2-AG, meta-analysis, theory, causation
Online: 11 July 2018 (11:49:02 CEST)
Obesity is treatment-resistant, and is linked with a number of serious, chronic diseases. Adult obesity rates in the United States have tripled since the early 1960s. Recent reviews show that an increased ratio of omega-6 to omega-3 fatty acids contributes to obesity rates by increasing levels of the endocannabinoid signals AEA and 2-AG, overstimulating CB1R and leading to increased caloric intake, reduced metabolic rates, and weight gain. Cannabis, or THC, also stimulates CB1R and increases caloric intake during acute exposures. The present meta-analysis reveals significantly reduced body mass index and rates of obesity in Cannabis users, in conjunction with increased caloric intake. We provide for the first time a causative explanation for this paradox, in which rapid and long-lasting downregulation of CB1R following acute Cannabis consumption reduces energy intake and storage and increases metabolic rates, thus reversing the impact on body mass index of elevated dietary omega-6/omega-3 ratios.
Subject: Chemistry, Analytical Chemistry Keywords: screen printed electrodes; Ag nanoparticles; drop-casting; spin-coating; nanoprisms; heavy metals; Differential pulse anodic stripping voltammetric; electrocatalysis
Online: 5 August 2019 (04:55:05 CEST)
The screen-printed carbon nanofibers electrodes (SPCNFE) represent an alternative with great acceptance due to their results, as well as their low impact for the environment. In order to improve their performance, in the present work they were modified with silver nanoparticles (Ag-NPs) and electrochemically characterized by using anodic stripping voltammetry. From the Ag-NPs synthesis, silver seeds (Ag-NS) and silver nanoprisms (Ag-NPr) were obtained. The Ag-NPs formation was confirmed by micrographs where Ag-NPs with diameters of 12.20±0.04 nm for Ag-NS, and 20.40±0.09 nm for Ag-NPr were observed. The electrodes were modified by using three different deposition methods: drop-casting, spin-coating and in-situ approaches. It was observed that the last methodology showed a low amount of Ag-NS deposited on the electrode surface and a deep alteration of this surface. Those facts suggested that the in situ synthesis methodology were not appropriate for the determination of heavy metals and it was discarded. The incorporation of the nanoparticles by spin-coating and drop-casting strategies showed different spatial distribution on the electrode surface as proved by scanning electron microscopy. The electrodes modified by these strategies, were evaluated for the cadmium(II) and lead(II) detection using differential pulse anodic stripping voltammetry, obtaining detection limit values of 2.1 and 2.8 µg L-1, respectively. The overall results showed that the incorporation route does not change directly the electrocatalytic effect of the nanoparticles, but the shape of these nanoparticles (spherical for seeds and triangular for prisms) has a preferential electrocatalytical enhancement over Cd(II) or Pb(II).
ARTICLE | doi:10.20944/preprints201804.0145.v1
Subject: Mathematics & Computer Science, Analysis Keywords: convex functions; AG, AH-convex functions; GA, GG, GH -convex functions and HA, HG, HH-convex function; integral inequalities
Online: 11 April 2018 (08:46:29 CEST)
In this paper we obtain some inequalities of Hermite-Hadamard type for composite convex functions. Applications for AG, AH-convex functions, GA, GG, GH-convex functions and HA, HG, HH-convex function are given. Applications for p, r-convex and LogExp functions are presented as well.
ARTICLE | doi:10.20944/preprints201810.0470.v1
Subject: Earth Sciences, Geology Keywords: Au-Ag low-sulphidation epithermal mineralization; Kremnica; gold; selenium; clausthalite; naumannite; miargyrite; pyrargyrite-proustite; polybasite-pearceite; diaphorite; Pb-Sb sulphosalts
Online: 22 October 2018 (05:35:42 CEST)
Selenium-rich Au-Ag mineralization has been discovered in the Kremnica ore district, central Slovakia. The mineralization is hosted by a single quartz-dolomite vein hosted by Neogene propyllitized andesites of the Kremnica stratovolcano. Ore mineralogy and crystal chemistry of individual ore minerals have been studied here. The early base-metal ore mineralization composed of pyrite, sphalerite and chalcopyrite lacks selenium, whereas the superimposed Au-Ag paragenesis is Se-enriched. The Au-Ag alloys, uytenbogaardtite, minerals of the galena-clausthalite series, acanthite-naumannite series, diaphorite, miargyrite, pyrargyrite-proustite, polybasite group, minerals of the tetrahedrite group and andorite branch (andorite IV, andorite VI, Ag-excess fizélyite), freislebenite, and rare Pb-Sb sulphosalts (scaiinite, robinsonite, plagionite) have been identified here. Besides selenides, the most Se-enriched phases are miargyrite, proustite-pyrargyrite, and polybasite-pearceite, whose Se contents are among the highest reported worldwide. In addition, one new phase has been found, corresponding to a Se-analogue of pearceite containing 2.08 - 3.54 apfu Se. The style of mineralization, paragenetic situation, and chemical trends observed in individual minerals are comparable to those of Au-Ag low-sulphidation epithermal Au-Ag mineralizations of the Kremnica and neighboring Štiavnica and Hodruša-Hámre Ore Districts, however, the pronounced enrichment in selenium is a specific feature of the studied vein only.
ARTICLE | doi:10.20944/preprints201806.0442.v1
Subject: Mathematics & Computer Science, Analysis Keywords: convex functions; AG, AH-h-convex functions; GA, GG, GH-h-convex functions and HA, HG, HH-h-convex function; integral inequalities
Online: 27 June 2018 (10:45:17 CEST)
In this paper we obtain some inequalities of Hermite-Hadamard type for composite convex functions. Applications for AG, AH-h-convex functions, GA, GG, GH-h-convex functions and HA, HG, HH-h-convex function are given.
REVIEW | doi:10.20944/preprints201906.0262.v1
Subject: Medicine & Pharmacology, Veterinary Medicine Keywords: endocannabinoid system; anandamide; 2-AG; cannabis; cannabinoid receptor 1; cannabinoid receptor 2; PPARSa, b; Ht1a; TRPV1; GPR55; cannabidiol; CBD; THC; CBG; CBC; tetrahydrocannabinol
Online: 26 June 2019 (07:28:52 CEST)
The endocannabinoid system has been found to be pervasive in mammalian species. It has also been described in invertebrate species primitive as the Hydra. Insects apparently are devoid of this otherwise ubiquitous system that provides homeostatic balance to the nervous and immune systems, as well as many other organ systems. The endocannabinoid system (ECS) has been defined to consist of three parts: 1. Endogenous ligands, 2. G-protein coupled receptors (GPCRs), and 3. Enzymes to degrade and recycle the ligands. Two endogenous molecules have been identified as ligands in the ECS to date. These are the endocannabinoids: Anandamide (arachidonoyl ethanolamide) and 2-AG (2-arachidonoyl glycerol). Two G-coupled protein receptors have been described as part of this system, with other putative GPC being considered. Coincidentally, the phytochemicals produced in large quantities by the Cannabis sativa L plant, and in lesser amounts by other plants, can interact with this system as ligands. These plant-based cannabinoids are termed, phytocannabinoids. The precise determination of the distribution of cannabinoid receptors in animal species is an ongoing project, with the canine cannabinoid receptor distribution currently receiving the most interest in non-human animals.