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Raman spectroscopy

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https://www.readbyqxmd.com/read/28449325/electrosynthesis-of-bifunctional-ws3-x-rgo-hybrid-for-her-and-orr-electrocatalysis
#1
Martin Pumera
We combined the desirable properties of tungsten sulfide and reduced graphene oxide (rGO) and fabricated the hybrid materials through simultaneous electrochemical reduction and synthesis, as a versatile and environmentally benign alternative to conventional fabrication techniques. We synthesised a mixed WS2/WS3 film-like material (WS3-x) directly onto GO-modified glassy carbon electrodes via cyclic voltammetry (CV) and the resultant hybrid materials (WS3-x/rGO) were thoroughly characterised using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) as well as Raman spectroscopy...
April 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28448887/macro-raman-spectroscopy-for-bulk-composition-and-homogeneity-analysis-of-multi-component-pharmaceutical-powders
#2
Hui Wang, David Barona, Sulayman Oladepo, Lisa Williams, Susan Hoe, David Lechuga-Ballesteros, Reinhard Vehring
A new macro-Raman system equipped with a motorized translational sample stage and low-frequency shift capabilities was developed for bulk composition and homogeneity analysis of multi-component pharmaceutical powders. Different sampling methods including single spot and scanning measurement were compared. It was found that increasing sample volumes significantly improved the precision of quantitative composition analysis, especially for poorly mixed powders. The multi-pass cavity of the macro-Raman system increased effective sample volumes by 20 times from the sample volume defined by the collection optics, i...
April 23, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28447704/influence-of-dopants-on-the-impermeability-of-graphene
#3
S S K Mallineni, D W Boukhvalov, I S Zhidkov, A I Kukharenko, A I Slesarev, A F Zatsepin, S O Cholakh, A M Rao, S M Serkiz, S Bhattacharya, E Z Kurmaev, R Podila
Graphene has attracted much attention as an impermeable membrane and a protective coating against oxidation. While many theoretical studies have shown that defect-free graphene is impermeable, in reality graphene inevitably has defects in the form of grain boundaries and vacancies. Here, we study the effects of N-dopants on the impermeability of few-layered graphene (FLG) grown on copper using chemical vapor deposition. The grain boundaries in FLG have minimal impact on their permeability to oxygen as they do not provide a continuous channel for gas transport due to high tortuosity...
April 27, 2017: Nanoscale
https://www.readbyqxmd.com/read/28447129/comparison-between-non-invasive-methods-used-on-paintings-by-goya-and-his-contemporaries-hyperspectral-imaging-vs-point-by-point-spectroscopic-analysis
#4
Floréal Daniel, Aurélie Mounier, Josefina Pérez-Arantegui, Carlos Pardos, Nagore Prieto-Taboada, Silvia Fdez-Ortiz de Vallejuelo, Kepa Castro
The development of non-invasive techniques for the characterization of pigments is crucial in order to preserve the integrity of the artwork. In this sense, the usefulness of hyperspectral imaging was demonstrated. It allows pigment characterization of the whole painting. However, it also sometimes requires the complementation of other point-by-point techniques. In the present article, the advantages of hyperspectral imaging over point-by-point spectroscopic analysis were evaluated. For that purpose, three paintings were analysed by hyperspectral imaging, handheld X-ray fluorescence and handheld Raman spectroscopy in order to determine the best non-invasive technique for pigment identifications...
April 26, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28446000/structural-modification-of-single-layer-graphene-under-laser-irradiation-featured-by-micro-raman-spectroscopy
#5
Yurii Stubrov, Andrii Nikolenko, Viktor Strelchuk, Sergii Nedilko, Vitalii Chornii
Confocal micro-Raman spectroscopy is used as a sensitive tool to study the nature of laser-induced defects in single-layer graphene. Appearance and drastic intensity increase of D- and D' modes in the Raman spectra at high power of laser irradiation is related to generation of structural defects. Time- and power-dependent evolution of Raman spectra is studied. The dependence of relative intensity of defective D- and D' bands is analyzed to relate the certain types of structural defects. The surface density of structural defects is estimated from the intensity ratio of D- and G bands using the D-band activation model...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28445998/infrared-raman-and-magnetic-resonance-spectroscopic-study-of-sio2-c-nanopowders
#6
Dariya Savchenko, Vladimir Vorliček, Ekaterina Kalabukhova, Aleksandr Sitnikov, Andrii Vasin, Dmytro Kysil, Stanislav Sevostianov, Valentyn Tertykh, Alexei Nazarov
Optical and magnetic properties of SiO2:C nanopowders obtained by chemical and thermal modification of fumed silica were studied by Fourier transform infrared spectroscopy, Raman, continuous wave (CW) electron paramagnetic resonance (EPR), echo-detected EPR and pulsed electron nuclear double resonance (ENDOR) spectroscopy. Two overlapping signals of Lorentzian lineshape were detected in CW EPR spectra of the initial SiO2:C. The EPR signal at g = 2.0055(3) is due to the silicon dangling bonds, which vanishes after thermal annealing, and the second EPR signal at g = 2...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28445634/low-temperature-associated-interface-influence-on-the-black-phosphorus-nanoflakes
#7
Peng Huang, Dan Guo, Guoxin Xie
The temperature dependent structure properties of few-layer black phosphorus (BP) nanoflakes supported on the Si substrate and suspended on the holes are investigated using the Raman spectroscopy in the range of 77-293 K. The temperature coefficients of three main Raman modes for supported BP are larger than those of suspended BP because of the interface effects, mainly the tensile strain and the different thermal expansion coefficients (TEC) between the substrate and BP nanoflakes. The out-of-plane vibration is more apt to be affected by the initial strain while the influence on the in-plane vibrations is negligible...
April 26, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28445606/structural-and-biological-properties-of-thermosensitive-chitosan-graphene-hybrid-hydrogels-for-sustained-drug-delivery-applications
#8
Leyla Saeednia, Li Yao, Marcus Berndt, Kim Cluff, Ramazan Asmatulu
Chitosan has the ability to make injectable thermosensitive hydrogels which has been highly investigated for drug delivery applications. The addition of nanoparticles is one way to increase the mechanical strength of thermosensitive chitosan hydrogel and subsequently and control the burst release of drug. Graphene nanoparticles have shown unique mechanical, optical and electrical properties which can be exploited for biomedical applications, especially in drug delivery. This study, have focused on the mechanical properties of a thermosensitive and injectable hybrid chitosan hydrogel incorporated with graphene nanoparticles...
April 26, 2017: Journal of Biomedical Materials Research. Part A
https://www.readbyqxmd.com/read/28445394/spectroscopic-detection-of-glyphosate-in-water-assisted-by-laser-ablated-silver-nanoparticles
#9
Rafael Eleodoro De Góes, Marcia Muller, José Luís Fabris
Glyphosate is one of the most widely used herbicides in the world. Its safety for both human health and aquatic biomes is a subject of wide debate. There are limits to glyphosate's presence in bodies of water, and it is usually detected through complex analytical procedures. In this work, the presence of glyphosate is detected directly through optical interrogation of aqueous solution. For this purpose, silver nanoparticles were produced by pulsed laser ablation in liquids. Limits of detection of 0.9 mg/L and 3...
April 26, 2017: Sensors
https://www.readbyqxmd.com/read/28443936/effects-of-graphene-defects-on-gas-sensing-properties-towards-no2-detection
#10
Filiberto Ricciardella, Sten Vollebregt, Tiziana Polichetti, Mario Miscuglio, Brigida Alfano, Maria L Miglietta, Ettore Massera, Girolamo Di Francia, Pasqualina M Sarro
The crystal structure of graphene flakes is expected to significantly affect their sensing properties. Here we report an experimental investigation on the crystalline structure of graphene aimed at exploring the effects on the gas sensing properties. The morphology of graphene, prepared via Chemical Vapor Deposition (CVD), Liquid Phase Exfoliation (LPE) and Mechanical Exfoliation (ME), is inspected through Raman spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). CVD and LPE-graphene structures are found to be more defective with respect to ME-graphene...
April 26, 2017: Nanoscale
https://www.readbyqxmd.com/read/28443855/dielectric-functions-and-critical-points-of-crystalline-ws2-ultrathin-films-with-tunable-thickness
#11
Da-Hai Li, Hua Zheng, Zi-Yi Wang, Rong-Jun Zhang, Hao Zhang, Yu-Xiang Zheng, Song-You Wang, David Wei Zhang, Liang-Yao Chen
Centimeter-scale WS2 ultrathin films were synthesized on sapphire substrates, and they showed highly oriented crystallographic growth along the c axis. Afterwards, the as-grown samples were systematically characterized using various detection methods. Reliable values of the roughness layer thickness and the film thickness were extracted using both atomic force microscopy (AFM) and spectroscopic ellipsometry (SE), and identified using Raman spectroscopy as well. The expansion and tensile strain along the [001] direction were discovered using X-ray diffraction (XRD) measurements...
April 26, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28443848/semiempirical-modeling-of-electrochemical-charge-transfer
#12
Rebecca L Gieseking, Mark A Ratner, George C Schatz
Nanoelectrochemical experiments using detection based on tip enhanced Raman spectroscopy (TERS) show a broad distribution of single-molecule formal potentials E°' for large π-conjugated molecules; theoretical studies are needed to understand the origins of this distribution. In this paper, we present a theoretical approach to determine E°' for electrochemical reactions involving a single molecule interacting with an electrode represented as a metal nanocluster and apply this method to the Ag20-pyridine system...
April 26, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28441872/unraveling-the-nature-of-anomalously-fast-energy-storage-in-t-nb2o5
#13
Dongchang Chen, Jeng-Han Wang, Tsung-Fu Chou, Bote Zhao, Mostafa A El-Sayed, Meilin Liu
While T-Nb2O5 has been frequently reported to display an exceptionally fast rate of Li-ion storage (similar to a capacitor), the detailed mechanism of the energy storage process is yet to be unraveled. Here we report our findings in probing the nature of the ultrafast Li-ion storage in T-Nb2O5 using both experimental and computational approaches. Experimentally, we used in operando Raman spectroscopy performed on a well-designed model cell to systematically characterize the dynamic evolution of vibrational band groups of T-Nb2O5 upon insertion and extraction of Li ions during repeated cycling...
April 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28441733/bioactivity-studies-on-titania-coatings-and-the-estimation-of-their-usefulness-in-the-modification-of-implant-surfaces
#14
Aleksandra Radtke, Adrian Topolski, Tomasz Jędrzejewski, Wiesław Kozak, Beata Sadowska, Marzena Więckowska-Szakiel, Piotr Piszczek
Morphologically different titania coatings (nanofibers (TNFs), nanoneedles (TNNs), and nanowires (TNWs)) were studied as potential biomedical materials. The abovementioned systems were produced in situ on Ti6Al4V substrates via direct oxidation processes using H₂O₂ and H₂O₂/CaCl₂ agents, and via thermal oxidation in the presence of Ar and Ar/H₂O₂. X-ray diffraction and Raman spectroscopy have been used to structurally characterize the produced materials. The morphology changes on the titanium alloy surface were investigated using scanning electron microscopy...
April 22, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28441033/surface-enhanced-raman-scattering-sers-active-gold-nanoparticles-decorated-on-a-porous-polymer-filter
#15
Lei Chen, Huiying Yan, Xiangxin Xue, Dayu Jiang, Yuxi Cai, Dongmei Liang, Young Mee Jung, Xiao Xia Han, Bing Zhao
In this work, we designed a process to assemble gold nanoparticles onto a three-dimensional (3D) polymer surface, which can then be monitored using surface-enhanced Raman scattering (SERS). This work is the first demonstration of the assembly of gold nanoparticles on a filter film and in situ measurement with Raman spectroscopy. Herein, a polyhexamethylene adipamide (Nylon66) film embedded in the organic filter film was used as a template to fabricate a tunable SERS-active substrate. A "hotspot"-rich gold-nanoparticle-decorated polymer substrate for SERS was prepared; this substrate exhibited high sensitivity in trace detection of targets...
January 1, 2017: Applied Spectroscopy
https://www.readbyqxmd.com/read/28441025/structures-interconversions-and-spectroscopy-of-iron-carbonyl-clusters-with-an-interstitial-carbide-localized-metal-center-reduction-by-overall-cluster-oxidation
#16
Subramaniam Kuppuswamy, Joshua D Wofford, Chris Joseph, Zhu-Lin Xie, Azim K Ali, Vincent M Lynch, Paul A Lindahl, Michael J Rose
The syntheses, interconversions, and spectroscopic properties of a set of iron carbonyl clusters containing an interstitial carbide are reported. This includes the low temperature X-ray structures of the six-iron clusters (Y)2[Fe6(μ6-C)(μ2-CO)4(CO)12] (1a-c; where Y = NMe4, NEt4, PPh4); the five-iron cluster [Fe5(μ5-C)(CO)15] (3); and the novel formulation of the five-iron cluster (NMe4)2[Fe5(μ5-C)(μ2-CO)(CO)13] (4). Also included in this set is the novel charge-neutral cluster, [Fe6(μ6-C)(CO)18] (2), for which we were unable to obtain a crystallographic structure...
April 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28440915/unravelling-the-impact-of-lignin-on-cell-wall-mechanics-a-comprehensive-study-on-young-poplar-trees-downregulated-for-cinnamyl-alcohol-dehyrogenase-cad
#17
M Özparpucu, M Rüggeberg, N Gierlinger, I Cesarino, R Vanholme, W Boerjan, I Burgert
Lignin engineering is a promising tool to reduce the energy input and the need of chemical pre-treatments for the efficient conversion of plant biomass into fermentable sugars for downstream applications. At the same time, lignin engineering can offer new insight into structure-function relationships of plant cell walls by combined mechanical, structural and chemical analyses. Here, such a comprehensive approach was applied on poplar trees (Populus tremula x Populus alba) downregulated for CINNAMYL ALCOHOL DEHYDROGENASE (CAD) for gaining insight into the impact of lignin reduction on mechanical properties...
April 25, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28440832/nanoemitters-and-innate-immunity-the-role-of-surfactants-and-bio-coronas-in-myeloperoxidase-catalyzed-oxidation-of-pristine-single-walled-carbon-nanotubes
#18
Cheuk Fai Chiu, Haider H Dar, Alexandr A Kapralov, Renã A S Robinson, Valerian E Kagan, Alexander Star
Single-walled carbon nanotubes (SWCNTs) are experimentally utilized in in vivo imaging and photothermal cancer therapy owing to their unique physicochemical and electronic properties. For these applications, pristine carbon nanotubes are often modified by polymer surfactant coatings to improve their biocompatibility, adding more complexity to their recognition and biodegradation by immuno-competent cells. Here, we investigate the oxidative degradation of SWCNTs catalyzed by neutrophil myeloperoxidase (MPO) using bandgap near-infrared (NIR) photoluminescence and Raman spectroscopy...
April 25, 2017: Nanoscale
https://www.readbyqxmd.com/read/28440049/analytical-based-methodologies-for-examining-the-in-vitro-absorption-distribution-metabolism-and-elimination-adme-of-silver-nanoparticles
#19
Sesha L A Paluri, John D Ryan, Nhi H Lam, Dhriti Nepal, Ioana E Sizemore
The clinical applications of silver nanoparticles (AgNPs) remain limited due to the lack of well-established methodologies for studying their nanokinetics. Hereby, the primary goal is to adapt a suite of analytical-based methodologies for examining the in vitro absorption, distribution, metabolism, and elimination of AgNPs. Vero 76 and HEK 293 cells are exposed to ≈10-nm spherical AgNPs(+) and AgNPs(-) at relevant concentrations (0-300 µg mL(-1) ) and times (4-48 h). Absorption: Inductively coupled plasma optical emission spectroscopy (ICP-OES) demonstrates that the two AgNP formulations are not bioequivalent...
April 25, 2017: Small
https://www.readbyqxmd.com/read/28439768/discrimination-of-wine-lactic-acid-bacteria-by-raman-spectroscopy
#20
Susan B Rodriguez, Mark A Thornton, Roy J Thornton
Species of Lactobacillus, Pediococcus, Oenococcus, and Leuconostoc play an important role in winemaking, as either inoculants or contaminants. The metabolic products of these lactic acid bacteria have considerable effects on the flavor, aroma, and texture of a wine. However, analysis of a wine's microflora, especially the bacteria, is rarely done unless spoilage becomes evident, and identification at the species or strain level is uncommon as the methods required are technically difficult and expensive. In this work, we used Raman spectral fingerprints to discriminate 19 strains of Lactobacillus, Pediococcus, and Oenococcus...
April 24, 2017: Journal of Industrial Microbiology & Biotechnology
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