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Raman spectra

Yuan Huang, Xiao Wang, Xu Zhang, Xianjue Chen, Baowen Li, Bin Wang, Ming Huang, Chongyang Zhu, Xuewei Zhang, Wolfgang S Bacsa, Feng Ding, Rodney S Ruoff
Raman spectra of large graphene bubbles showed size-dependent oscillations in spectral intensity and frequency, which originate from optical standing waves formed in the vicinity of the graphene surface. At a high laser power, local heating can lead to oscillations in the Raman frequency and also create a temperature gradient in the bubble. Based on Raman data, the temperature distribution within the graphene bubble was calculated, and it is shown that the heating effect of the laser is reduced when moving from the center of a bubble to its edge...
May 4, 2018: Physical Review Letters
S Trautmann, M Richard-Lacroix, A Dathe, H Schneidewind, J Dellith, W Fritzsche, V Deckert
The optical response of realistic 3D plasmonic substrates composed of randomly shaped particles of different size and interparticle distance distributions in addition to nanometer scale surface roughness is intrinsically challenging to simulate due to computational limitations. Here, we present a Finite Element Method (FEM)-based methodology that bridges in-depth theoretical investigations and experimental optical response of plasmonic substrates composed of such silver nanoparticles. Parametrized scanning electron microscopy (SEM) images of surface enhanced Raman spectroscopy (SERS) active substrate and tip-enhanced Raman spectroscopy (TERS) probes are used to simulate the far-and near-field optical response...
May 18, 2018: Nanoscale
Jessica D Flynn, Jennifer C Lee
Structural differences in pathological and functional amyloid fibrils have been investigated by Raman microspectroscopy. Second-derivative analyses of amide-I and amide-III bands distinguish parallel in-register β-sheets from a β-solenoid. Further, spatially resolved Raman spectra reveal molecular heterogeneity in amyloid structures.
May 18, 2018: Chemical Communications: Chem Comm
Sariga C Lal, Vidhya Lalan, Subodh Ganesanpotti
Ba2 Ln2/3 TeO6 (Ln = La, Pr, Nd, Sm, and Eu) double perovskites were synthesized via solid-state ceramic route. Preliminary X-ray diffraction studies indicated a pseudocubic structure with lattice parameters ranging from 8.55 to 8.44 Å for the substitution of rare earths from La to Eu. Raman spectra show the frequency dependence of various Raman bands with respect to rare-earth substitution and exhibit a significant shift in peaks to higher wavenumber region, which was observed only for symmetric stretching modes of LnO6 and TeO6 octahedra...
May 17, 2018: Inorganic Chemistry
Chan Gao, Xueyong Zhang, Chuanchao Zhang, Zhilei Sui, Meng Hou, Rucheng Dai, Zhongping Wang, Xianxu Zheng, Zengming Zhang
Herein, pressure-induced phase transitions of RDX up to 50 GPa were systematically studied under different compression conditions. Precise phase transition points were obtained based on high-quality Raman spectra with small pressure intervals. This favors the correctness of the theoretical formula for detonation and the design of a precision weapon. The experimental results indicated that α-RDX immediately transformed to γ-RDX at 3.5 GPa due to hydrostatic conditions and possible interaction between the penetrating helium and RDX, with helium gas as the pressure-transmitting medium (PTM)...
May 17, 2018: Physical Chemistry Chemical Physics: PCCP
Sarvottam K Jha, Reetu Kumari, Shubham Choudhary, Puspendu Guha, P V Satyam, Brajesh S Yadav, Zainab Naqvi, S S Kushvaha, R K Ratnesh, M S Mehata, Aditya Jain, Amrish K Panwar, Fouran Singh, Pawan K Tyagi
In this paper, we have reported a simple and efficient method for the synthesis of uniform, highly conducting single or few layer molybdenum disulfide (MoS2) on large scale. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) have been used for the confirmation of mono or few layered nature of the as-synthesized MoS2 sheets. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Raman Spectroscopy have also been used to study the elemental, phase, and molecular composition of the sample...
January 1, 2018: Journal of Nanoscience and Nanotechnology
Yunjie Xu, Angelo Shehan Perera, Joseph Cheramy, Christian Merten, Javix Thomas
Solvent effects, in particular those involving water as the solvent, are of significant interest to chemistry and physics communities. IR, vibrational circular dichroism (VCD), Raman, and Raman optical activity (ROA) spectra of methyl glycidate in two very different solvents, namely CCl4 and water, have been measured experimentally and simulated theoretically. While the observed spectra in CCl4 could be well modelled using the polarizable continuum model for the solvent, the situation is much different in water...
May 16, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Diane M Haiber, Peter A Crozier
In graphitic carbon nitrides, (photo)catalytic functionality is underpinned by the effect that residual hydrogen content, manifesting in amine (N-Hx ) defects, has on its optoelectronic properties. Therefore, a detailed understanding of the variation in the local structure of graphitic carbon nitrides is key for understanding structure-activity relationships. Here we apply aloof-beam vibrational electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM) to locally detect variations in hydrogen content in two different layered carbon nitrides with nanometer resolution...
May 16, 2018: ACS Nano
Suzuko Yamazaki, Dai Shimizu, Seiji Tani, Kensuke Honda, Michinori Sumimoto, Kenji Komaguchi
Tungsten oxide-based photochromic films which change reversibly in air between colorless-transparent in the dark and dark blue under UV irradiation were prepared by using methylcellulose as a film matrix and various dispersants. Alpha-hydroxyl acid like glycolic acid (GA) or glyceric acid (GlyA) is the best dispersant because it can make the film transparent by adding a small quantity much less than that of 3-hydroxypropionic acid or ethylene glycol. Fourier-transform infrared spectra and Raman spectra indicate that a strong interaction exists between WO3 and GA or GlyA...
May 16, 2018: ACS Applied Materials & Interfaces
Stewart F Parker, Lisha Zhong
In this work, we have used a combination of vibrational spectroscopy (infrared, Raman and inelastic neutron scattering) and periodic density functional theory to investigate six metal methanesulfonate compounds that exhibit four different modes of complexation of the methanesulfonate ion: ionic, monodentate, bidentate and pentadentate. We found that the transition energies of the modes associated with the methyl group (C-H stretches and deformations, methyl rock and torsion) are essentially independent of the mode of coordination...
April 2018: Royal Society Open Science
Abdulmujeeb T Onawole, Saheed A Popoola, Tawfik A Saleh, Abdulaziz A Al-Saadi
Vibrational infrared, Raman and surface-enhanced Raman scattering (SERS) spectra of clotrimazole (CTZ) were documented and evaluated. Density-functional theory, B3LYP/6-311++G(d,p), approach was implemented to identify the possible conformations, develop the electrostatic potential map, evaluate frontier molecular orbitals and calculate the vibrational spectra of the target compound. The silver-loaded graphene was shown to be an effective SERS substrate for CTZ trace detection. The SERS spectrum showed two enhanced bands at 670 cm-1 and 700 cm-1 which confirmed the absorption of the silver substrate through chlorine and nitrogen atoms...
May 7, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Wioleta Edyta Śmiszek-Lindert, Elżbieta Chełmecka, Olaf Lindert, Anna Dudzińska, Ilona Kaczmarczyk-Sedlak
This paper presents the investigation results of the polarized IR spectra of the hydrogen bond in crystals of N-acetylbenzylamine and its sulphur analogue N-benzyl-ethanethioamide. The spectra were measured at 298 and 77 K by a transmission method, with the use of polarized light. The Raman spectroscopy, Hirshfeld surfaces analysis and DFT studies have been also reported. Theoretical calculations of the isolated molecule were performed by using density functional theory (DFT) method at B3LYP/6-311(d,p), B3LYP/6-311++G(d,p) and B3LYP/6-311++G(3df,2pd) basis set levels...
May 8, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Vitaly I Korepanov, Daria M Sedlovets
Asymmetric lineshapes are experimentally observed in the Raman spectra of different classes of condensed matter. Determination of the peak parameters, typically done with symmetric pseudo-Voigt functions, in such situations yields unreliable results. While a wide choice of asymmetric fitting functions is possible, for the function to be practically useful, it should satisfy several criteria: simple analytic form, minimum parameters, description of the symmetric shape as "zero case", estimation of the desired peak parameters in a straightforward way and, above all, adequate description of the experimental data...
May 15, 2018: Analyst
Tao Wang, Juhong Zhou, Yan Wang
Ag⁻Pt nanoparticles, grafted on Ge wafer, were synthesized by the galvanic replacement reaction based on their different potentials. Detailed characterization through scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray photo-elelctron spectroscopy (XPS) proved that Ag⁻Pt nanoparticles are composed of large Ag nanoparticles and many small Pt nanoparticles instead of an Ag⁻Pt alloy. When applied as surface-enhanced Raman scattering (SERS) substrates to detect Rhodamine 6G (1 × 10-8 M) or Crystal violet (1 × 10-7 M) aqueous solution in the line mapping mode, all of the obtained relative standard deviation (RSD) values of the major characteristic peak intensities, calculated from the SERS spectra of 100 serial spots, were less than 10%...
May 15, 2018: Nanomaterials
Ortrud Uckermann, Wenmin Yao, Tareq A Juratli, Roberta Galli, Elke Leipnitz, Matthias Meinhardt, Edmund Koch, Gabriele Schackert, Gerald Steiner, Matthias Kirsch
INTRODUCTION: Mutations in the isocytrate dehydrogenase 1 (IDH1) gene are early genetic events in glioma pathogenesis and cause profound metabolic changes. Because this genotype is found in virtually every tumor cell, therapies targeting mutant IDH1 protein are being developed. The intraoperative administration of those therapies would require fast technologies for the determination of IDH1 genotype. As of today, there is no such diagnostic test available. Recently, infrared spectroscopy was shown to bridge this gap...
May 14, 2018: Journal of Neuro-oncology
Anabia Sohail, Saranjam Khan, Rahat Ullah, Shahzad Ahmad Qureshi, Muhammad Bilal, Asifullah Khan
This work presents a diagnostic system for the hepatitis C infection using Raman spectroscopy and proximity based classification. The proposed method exploits transformed Raman spectra using the proximity based machine learning technique and is denoted as RS-PCA-Prox. First, Raman spectral data is baseline corrected by subtracting noise and low intensity background. After this, a feature transformation of Raman spectra is adopted, not only to reduce the feature's dimensionality but also to learn different deviations in Raman shifts...
May 1, 2018: Biomedical Optics Express
Xiwen Gong, Oleksandr Voznyy, Ankit Jain, Wenjia Liu, Randy Sabatini, Zachary Piontkowski, Grant Walters, Golam Bappi, Sergiy Nokhrin, Oleksandr Bushuyev, Mingjian Yuan, Riccardo Comin, David McCamant, Shana O Kelley, Edward H Sargent
Low-dimensional perovskites have-in view of their high radiative recombination rates-shown great promise in achieving high luminescence brightness and colour saturation. Here we investigate the effect of electron-phonon interactions on the luminescence of single crystals of two-dimensional perovskites, showing that reducing these interactions can lead to bright blue emission in two-dimensional perovskites. Resonance Raman spectra and deformation potential analysis show that strong electron-phonon interactions result in fast non-radiative decay, and that this lowers the photoluminescence quantum yield (PLQY)...
May 14, 2018: Nature Materials
Jie Sun, Shuyan Han, Ying Wang, Guanyu Zhao, Weiping Qian, Jian Dong
To detect the redox state evolution during wound healing process, a redox-sensitive surface-enhanced Raman scattering (SERS) probe was constructed by attaching anthraquinone as a redox-sensitive molecule onto gold nanoshells, and the redox-sensitive SERS probes were loaded on one surface of a chitosan membrane as a redox-sensitive wound dressing. The redox-sensitive wound dressing covered an acute wound as both a wound dressing and a redox state sensor. The spatiotemporal evolution of the redox states of the healing wound was obtained by collecting the SERS spectra of the SERS probes in situ and noninvasively...
May 14, 2018: Analytical Chemistry
Aleksandr S Oreshonkov, Evgenii Roginskii, Alexander S Krylov, Alexandr A Ershov, Vladimir Nikolaevich Voronov
Crystal structure of LaF3 single crystal is refined in tysonite-type trigonal unit cell P-3c1 using density functional theory calculations and Raman spectroscopy. It is shown that trigonal structure with P-3c1 space group is more energy-efficient than hexagonal structure with space group P63cm. Simulated Raman spectra obtained using LDA approximation is in much better agreement with experimental data than obtained with PBE and PBEsol functionals of GGA. The calculated frequency value of silent mode B2 in case of hexagonal structure P63cm was found to be imaginary (unstable mode), thus the energy surface obtains negative curvature with respect to the corresponding normal coordinates of the mode which leads to instability of the hexagonal structure in harmonic approximation...
May 14, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xiaoyun Chen, Donald Eldred, Jing Liu, Hsu Chiang, Xianghuai Wang, Mark A Rickard, Siyu Tu, Li Cui, Paul LaBeaume, Kwan Skinner
Sol-gels are found in many different scientific fields and have very broad applications. They are often prepared by the hydrolysis and condensation of alkoxysilanes such as trimethoxysilanes, which are commonly used as precursors in the preparation of silsequioxanes via the sol-gel process. The reaction rates of such reactions are influenced by a wide range of experimental factors such as temperature, pH, catalyst, etc. In this study, we combined multiple in situ spectroscopic techniques to monitor the hydrolysis and partial condensation reactions of methyltrimethoxysilane and phenyltrimethoxysilane...
January 1, 2018: Applied Spectroscopy
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