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Raman spectroscopy

Artem Grebenko, Vyacheslav Dremov, Petr Barzilovich, Anton Bubis, Konstantin Sidoruk, Tatiyana Voeikova, Zarina Gagkaeva, Timur Chernov, Evgeny Korostylev, Boris Gorshunov, Konstantin Motovilov
For decades respiratory chain and photosystems were the main firing field of the studies devoted to mechanisms of electron transfer in proteins. The concept of conjugated lateral electron and transverse proton transport during cellular respiration and photosynthesis, which was formulated in the beginning of 1960-s, has been confirmed by thousands of experiments. However, charge transfer in recently discovered bacterial nanofilaments produced by various electrogenic bacteria is regarded currently outside of electron and proton conjugation concept...
2018: PloS One
Sankar Raman Vaikuntam, Klaus Werner Stöckelhuber, Eshwaran Subramani Bhagavatheswaran, Sven Wiessner, Ulrich Scheler, Kay Saalwaechter, Petr Formanek, Gert Heinrich, Amit Das
A sol-gel transformation of liquid silica precursor to solid silica particles was carried out in a one pot synthesis way where a solution of styrene butadiene elastomer (S-SBR) was present. The composites, thus produced, offered remarkable improvements of mechanical and dynamic mechanical performances as compared with precipitated silica. The morphological analysis reveals that the alkoxy-based silica particles resemble a raspberry structure when the synthesis of the silica was carried out in presence of polymer molecules and represent a much more open silica-network structure...
January 19, 2018: Journal of Physical Chemistry. B
Shekhar Tyagi, Gaurav Sharma, Vasant G Sathe
The competition and cooperation between ferroelectric and antiferrodistortive (AFD) instabilities are studied using pressure dependent Raman spectroscopy on polycrystalline powder samples of Sr1-xCaxTiO3(x=0.0, 0.06, 0.25, 0.35). For x=0.0 composition, broad polar mode is detected in the Raman spectra above 6 GPa, while for x=0.06 composition the polar modes appear well above 9 GPa where the AFD modes showed strong suppression. In x=0.25 and 0.35 composition the application of small pressure results in appearance of strong AFD modes suppressing the polar modes...
January 19, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xi Rong, Fang Wei, Rui-Qiong Luo, Xue Yuan, Qi-Qi Kuang, Dong-Ping Yin, Shu-Shi Huang, Yue-Ming Jiang, Hong Liu
No abstract text is available yet for this article.
January 1, 2018: Applied Spectroscopy
M B Vrazo, A F Diefendorf, B E Crowley, A D Czaja
The Upper Cretaceous Coon Creek Lagerstätte of Tennessee, USA, is known for its extremely well-preserved mollusks and decapod crustaceans. However, the depositional environment of this unit, particularly its distance to the shoreline, has long been equivocal. To better constrain the coastal proximity of the Coon Creek Formation, we carried out a multiproxy geochemical analysis of fossil decapod (crab, mud shrimp) cuticle and associated sediment from the type section. Elemental analysis and Raman spectroscopy confirmed the presence of kerogenized carbon in the crabs and mud shrimp; carbon isotope (δ13 C) analysis of bulk decapod cuticle yielded similar mean δ13 C values for both taxa (-25...
January 19, 2018: Geobiology
Saheed Bukola, Ying Liang, Carol Korzeniewski, Joel Harris, Stephen Creager
Ion current densities near 1 A cm-2 at modest bias voltages (< 200 mV) are reported for proton and deuteron transmission across single-layer graphene in polyelectrolyte-membrane (PEM)-style hydrogen pump cells. The graphene is sandwiched between two Nafion membranes and covers the entire area between two platinum-carbon electrodes, such that proton transfer is forced to occur through the graphene layer. Raman spectroscopy confirms that buried graphene layers are single-layer and relatively free of defects following the hot-press procedure used to make the sandwich structures...
January 19, 2018: Journal of the American Chemical Society
Hyunjoong Chung, Dmytro Dudenko, Fengjiao Zhang, Gabriele D'Avino, Christian Ruzié, Audrey Richard, Guillaume Schweicher, Jérôme Cornil, David Beljonne, Yves Geerts, Ying Diao
Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition...
January 18, 2018: Nature Communications
D Smith, M A Hakeem, P Parisiades, H E Maynard-Casely, D Foster, D Eden, D J Bull, A R L Marshall, A M Adawi, R Howie, A Sapelkin, V V Brazhkin, J E Proctor
We report experimental evidence for a crossover between a liquidlike state and a gaslike state in fluid methane (CH_{4}). This crossover is observed in all of our experiments, up to a temperature of 397 K, 2.1 times the critical temperature of methane. The crossover has been characterized with both Raman spectroscopy and x-ray diffraction in a number of separate experiments, and confirmed to be reversible. We associate this crossover with the Frenkel line-a recently hypothesized crossover in dynamic properties of fluids extending to arbitrarily high pressure and temperature, dividing the phase diagram into separate regions where the fluid possesses liquidlike and gaslike properties...
November 2017: Physical Review. E
Jong Guk Kim, Youngmin Kim, Yuseong Noh, Seonhwa Lee, Yoongon Kim, Won Bae Kim
In this paper, bifunctional catalysts consisting of perovskite LaCo0.8Fe0.2O3 nanowires (LCFO NWs) with reduced graphene oxide (rGO) sheets were prepared for use in lithium-oxygen (Li-O2) battery cathodes. The structure and morphology of bifunctional LCFO@rGO catalysts were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The prepared LCFO@rGO composite was explored as a cathode catalyst for Li-O2 batteries, resulted in an outstanding discharge capacity (ca...
January 18, 2018: ACS Applied Materials & Interfaces
Shihua Yu, Zhigang Liu, Hongwei Li, Jianpo Zhang, Xin-Xin Yuan, Xiangyu Jia, Yuqing Wu
Surface enhanced Raman scattering (SERS) is an ultra-sensitive spectroscopy technique, which can provide rich structural information for a great number of molecules, while solid phase micro-extraction (SPME) is an efficient method for sample pretreatment in analytical chemistry, particularly in a micro-system. In the present report, a silver-loaded and graphene-based magnetic composite (Fe3O4@GO@Ag) was fabricated for use as both a SERS-active substrate and SPME material. The π-π stacking and fluorescence quenching abilities of GO make the composite a perfect candidate for SERS in analyzing real-world samples...
January 18, 2018: Analyst
Fernanda Rossi Paolillo, Renan Arnon Romano, Luciana de Matos, Airton Abrahão Martin, Francisco Eduardo Gontijo Guimarães, Jarbas Caiado de Castro Neto, Vanderlei Salvador Bagnato
There are few published data on the relationship between loss of bone mass due to osteoporosis and poor tooth quality. This study analyzed the effects of osteoporosis on incisor teeth and femoral bones using optical techniques in rats. Twenty female Wistar rats aged 6 months (n = 20) were randomized into two groups: control group, non-ovariectomized rats (n = 10); ovariectomy group, ovariectomized rats to induce osteoporosis (n = 10). Each group was subdivided randomly into two groups containing five rats each as follows...
January 17, 2018: Journal of Bone and Mineral Metabolism
Yulia Rosa Saharman, Anis Karuniawati, Rudyanto Sedono, Dita Aditianingsih, Pratiwi Sudarmono, Wil H F Goessens, Corné H W Klaassen, Henri A Verbrugh, Juliëtte A Severin
Background: Carbapenem-nonsusceptible A. baumannii-calcoaceticus complex have emerged worldwide, but the epidemiology in Indonesian hospitals has not been studied. Methods: A prospective observational study was performed on the intensive care units (ICUs) of the national referral hospital in Jakarta-Indonesia, in 2013 and 2014. All consecutive adult patients admitted and hospitalized for >48 h in ICUs were included. Basic and clinical data at admission were recorded...
2018: Antimicrobial Resistance and Infection Control
Daniel Sola, Lorena Grima
Bioactivity and ingrowth of ceramic implants is commonly enhanced by a suitable interconnected porous network. In this work, the laser machining of CaSiO₃‒Ca₃(PO₄)₂ biocompatible eutectic glass-ceramics and glasses was studied. For this purpose, 300 µm diameter craters were machined by using pulsed laser radiation at 532 nm with a pulsewidth in the nanosecond range. Machined samples were soaked in simulated body fluid for 2 months to assess the formation of a hydroxyapatite layer on the surface of the laser machined areas...
January 13, 2018: Materials
Xiaoxiao Hu, Peiquan Xu, Hongying Gong, Guotao Yin
Tungsten trioxide (WO₃) nanorods are synthesized on the surface of graphene (GR) sheets by using a one-step in-situ hydrothermal method employing sodium tungstate (Na₂WO₄·2H₂O) and graphene oxide (GO) as precursors. The resulting WO₃/GR nanocomposites are characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The results confirm that the interface between WO₃ nanorod and graphene contains chemical bonds...
January 17, 2018: Materials
Sathish Dharani, Ziyaur Rahman, Sogra F Barakh Ali, Hamideh Afrooz, Mansoor A Khan
Phenytoin sodium (PS) has tendency to convert to its base form; phenytoin base (PHT) during manufacturing, packaging, shelf life and in-use conditions that can influence its clinical performance. The objective of the present work was to develop a non-destructive, quick and easy analytical method for quantification of PHT in the drug product. A formulation was prepared containing the excipients present in the commercial capsule formulation of PS. Formulation containing either 100% PHT or PS was prepared and these formulations were mixed in different proportion to achieve 0-100% PHT matrices...
January 13, 2018: International Journal of Pharmaceutics
H-H Kung, S Maiti, X Wang, S-W Cheong, D L Maslov, G Blumberg
Using polarization-resolved resonant Raman spectroscopy, we explore collective spin excitations of the chiral surface states in a three dimensional topological insulator, Bi_{2}Se_{3}. We observe a sharp peak at 150 meV in the pseudovector A_{2} symmetry channel of the Raman spectra. By comparing the data with calculations, we identify this peak as the transverse collective spin mode of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface plasmon in the charge sector of excitations, is analogous to a spin wave in a partially polarized Fermi liquid, with spin-orbit coupling playing the role of an effective magnetic field...
September 29, 2017: Physical Review Letters
Sebastian Maehrlein, Alexander Paarmann, Martin Wolf, Tobias Kampfrath
In stimulated Raman scattering, two incident optical waves induce a force oscillating at the difference of the two light frequencies. This process has enabled important applications such as the excitation and coherent control of phonons and magnons by femtosecond laser pulses. Here, we experimentally and theoretically demonstrate the so far neglected up-conversion counterpart of this process: THz sum-frequency excitation of a Raman-active phonon mode, which is tantamount to two-photon absorption by an optical transition between two adjacent vibrational levels...
September 22, 2017: Physical Review Letters
C Cappuccino, P P Mazzeo, T Salzillo, E Venuti, A Giunchi, R G Della Valle, A Brillante, C Bettini, M Melucci, L Maini
This work presents a Raman based approach for the rapid identification of the molecular conformation in a series of new 2,3-thienoimide capped quaterthiophenes, whose crystal structures were determined by synchrotron radiation X-ray powder diffraction. These systems display two conformational polymorphs, known as forms A and B, as a result of the anti-anti-anti and syn-anti-syn arrangements of the quaterthiophene cores. In a micro-Raman and computational study, the spectroscopic differences between the conformers were detected and proved to be suitable markers for polymorph identification...
January 17, 2018: Physical Chemistry Chemical Physics: PCCP
D Errandonea, O Gomis, P Rodríguez-Hernández, A Muñoz, J Ruiz-Fuertes, M Gupta, S N Achary, A Hirsch, F J Manjon, L Peters, G Roth, A K Tyagi, M Bettinelli
Monazite-type BiPO4, LaPO4, CePO4, and PrPO4 have been studied under high pressure by ab initio simulations and Raman spectroscopy measurements in the pressure range of stability of the monazite structure. A good agreement between experimental and theoretical Raman-active mode frequencies and pressure coefficients has been found which has allowed us to discuss the nature of the Raman-active modes. Besides, calculations have provided us with information on how the crystal structure is modified by pressure. This information has allowed us to determine the equation of state and the isothermal compressibility tensor of the four studied compounds...
January 16, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Gang Qiu, Qiong Nian, Maithilee Motlag, Shengyu Jin, Biwei Deng, Yexin Deng, Adam R Charnas, Peide D Ye, Gary J Cheng
Few-layer black phosphorus (BP) has emerged as one of the most promising candidates for post-silicon electronic materials due to its outstanding electrical and optical properties. However, lack of large-scale BP thin films is still a major roadblock to further applications. The most widely used methods for obtaining BP thin films are mechanical exfoliation and liquid exfoliation. Herein, a method of directly synthesizing continuous BP thin films with the capability of patterning arbitrary shapes by employing ultrafast laser writing with confinement is reported...
January 16, 2018: Advanced Materials
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