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Raman spectra

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
Raushan Nurdillayeva, Atsinafe Oshido, Thomas Bamford, Osama El-Zubir, Andrew Houlton, John Hedley, Andrew Pike, Benjamin Horrocks
Cadmium sulfide can be templated on -DNA molecules to form an aqueous dispersion of CdS/-DNA nanowires. Subsequent addition of ethylene glycol to 50% v/v is sufficient to formulate an ink suitable for printing using piezoelectric drop-on-demand technology. Printed droplet arrays show a coffee-ring morphology of individual deposits by fluorescence and Raman microscopy, but upon increasing the number of layers of printed material by repeated printing over each droplet, the dry deposit approaches closer to a disc shape...
January 19, 2018: Nanotechnology
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
Martina Banchelli, Marella de Angelis, Cristiano D'Andrea, Roberto Pini, Paolo Matteini
An advanced optofluidic system for protein detection based on Raman signal amplification via dewetting and molecular gathering within temporary mesoscale assemblies is presented. The evaporation of a microliter volume of protein solution deposited in a circular microwell precisely follows an outward-receding geometry. Herein the combination of liquid withdrawal with intermolecular interactions induces the formation of self-assembled molecular domains at the solid-liquid interface. Through proper control of the evaporation rate, amplitude of the assemblies and time for spectral collection at the liquid edge are extensively raised, resulting in a local enhancement and refinement of the Raman response, respectively...
January 18, 2018: Scientific Reports
Xin Yu, Wei Li, Jian Huang, Zhonghua Li, Jiawen Liu, PingAn Hu
Superstructured mesocrystalline Ta2O5 nanosheets were successfully prepared from mesocrystalline (NH4)2Ta2O3F6 nanorods by the annealing method for the first time. The as-prepared mesocrystalline Ta2O5 nanosheets in this work showed remarkable visible light absorption, mainly due to the formation of oxygen vacancy defects in the mesocrystalline Ta2O5 nanosheets, which was also confirmed by XPS spectra, Raman spectra and EPR spectra. Besides, the mesocrystalline Ta2O5 nanosheets showed a highly enhanced photocatalytic activity of 11 268...
January 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Ying Zhang, Chengliang Yang, Bin Xue, Zenghui Peng, Zhaoliang Cao, Quanquan Mu, Li Xuan
We demonstrated flower-like 3D Ag-Au hetero-nanostructures on an indium tin oxide glass (ITO glass) for surface enhanced Raman scattering (SERS) applications. The flower-like 3D Ag nanostructures were obtained through electrodeposition with liquid crystalline soft template which is simple, controllable and cost effective. The flower-like 3D Ag-Au hetero-nanostructures were further fabricated by galvanic replacement reaction of gold (III) chloride trihydrate (HAuCl4·3H2O) solution and flower-like Ag. The flower-like Ag-Au hetero-nanostructure exhibited stronger SERS effects and better chemical stability compared with flower-like Ag nanostructure...
January 17, 2018: Scientific Reports
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
Yasutaka Kitahama, Tamitake Itoh, Toshiaki Suzuki
To evaluate the shape of an Ag tip with regard to tip-enhanced Raman scattering (TERS) signal, the enhanced electromagnetic (EM) field and scattering spectrum, arising from surface plasmon resonance at the apex of the tip, were calculated using a finite-difference time domain (FDTD) method. In the calculated forward scattering spectra from the smooth Ag tip, the band appeared within the visible region, similar to the experimental results and calculation for a corrugated Ag cone. In the FDTD calculation of TERS, the Ag tip acting as a monopole antenna was adopted by insertion of a perfect electric conductor between the root of the tip and a top boundary surface of the calculation space...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Alexander M Khenkin, Madhu Vedichi, Linda J W Shimon, Matthew A Cranswick, Johannes E M N Klein, Lawrence Que, Ronny Neumann
The iron(II) triflate complex (1) of 1,2-bis(2,2'-bipyridyl-6-yl)ethane, with two bipyridine moieties connected by an ethane bridge, was prepared. Addition of aqueous 30% H2O2 to an acetonitrile solution of 1 yielded 2, a green compound with λmax=710 nm. Moessbauer measurements on 2 showed a doublet with an isomer shift (δ) of 0.35 mm/s and a quadrupole splitting (ΔEQ) of 0.86 mm/s, indicative of an antiferromagnetically coupled diferric complex. Resonance Raman spectra showed peaks at 883, 556 and 451 cm-1 that downshifted to 832, 540 and 441 cm-1 when 1 was treated with H218O2...
November 2017: Israel Journal of Chemistry
Stephanie M Fowler, Heinar Schmidt, Remy van de Ven, David L Hopkins
A preliminary investigation was conducted to determine the potential for a handheld Raman spectroscopic device to predict sensory traits determined by an untrained consumer panel. Measurement of 45 beef loins (M. longissimus lumborum) was conducted using a 671nm handheld Raman spectroscopic device. Samples were then held frozen until testing by an untrained sensory panel. Sections were also excised to determine shear force values and other indicators of meat quality. Derived models suggest that the Raman spectroscopic device can predict juiciness and tenderness, with correlations between predicted and observed values (ρ) of 0...
January 3, 2018: Meat Science
Krzysztof Zdunek, Rafał Chodun, Bartosz Wicher, Katarzyna Nowakowska-Langier, Sebastian Okrasa
This paper presents the results of investigations of carbon films deposited by a modified version of the magnetron sputtering method - HiPGIMS (High Power Gas Injection Magnetron Sputtering). In this experiment, the magnetron system with inversely polarized electrodes (sputtered cathode at ground potential and positively biased, spatially separated anode) was used. This arrangement allowed us to conduct the experiment using voltages ranging from 1 to 2kV and a power supply system equipped with 25/50μF capacitor battery...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Weiping Ren, Wei Song, Sally Yurgelevic, David C Markel
We previously described the gelation mechanism of calcium polyphosphate (CPP) in the presence of water. In this study, we developed novel and injectable poly-dicalcium phosphate dihydrate (P-DCPD) forming cement by the reaction of acidic CPP gel with alkali tetracalcium phosphate (TTCP). The setting reaction mechanism of P-DCPD is due to the intermolecular interaction between CPP gel and TTCP that was supported by XRD, AFM, Raman spectra analysis and SEM. The setting mechanism of P-DCPD is completely different from the classical calcium phosphate cement (CPC) that achieves crystallization by monophosphates reaction...
January 4, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Surajit Kayal, Khokan Roy, Siva Umapathy
Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy...
January 14, 2018: Journal of Chemical Physics
Mauricelio Bezerra da Silva, Regina C R Santos, Paulo T C Freire, Ewerton W S Caetano, Valder N Freire
Boric acid (H3BO3) is being used effectively nowadays in traps/baits for the management of Aedes aegypti L. and Aedes albopictus Skuse species of mosquitoes, which are the main spreading vectors worldwide for diseases like malaria, dengue and zika. Previously, we have published results on the structural, electronic and optical properties of its molecular triclinic H3BO3-2A and trigonal H3BO3-3T polymorphs within the framework of density functional theory (DFT). Due to the renewed importance of these materials, the focus of this work is on the vibrational properties of the bulk boric acid 2A and 3T polymorphs...
January 12, 2018: Journal of Physical Chemistry. A
Chao-Bo Yang, Ping He, David Escofet-Martin, Jiang-Bo Peng, Rong-Wei Fan, Xin Yu, Derek Dunn-Rankin
In this paper, three ultrashort-pulse coherent anti-Stokes Raman scattering (CARS) thermometry approaches are summarized with a theoretical time-domain model. The difference between the approaches can be attributed to variations in the input field characteristics of the time-domain model. That is, all three approaches of ultrashort-pulse (CARS) thermometry can be simulated with the unified model by only changing the input fields features. As a specific example, the hybrid femtosecond/picosecond CARS is assessed for its use in combustion flow diagnostics; thus, the examination of the input field has an impact on thermometry focuses on vibrational hybrid femtosecond/picosecond CARS...
January 10, 2018: Applied Optics
M Nurul Abedin, Arthur T Bradley, Anupam K Misra, Yingxin Bai, Glenn D Hines, Shiv K Sharma
We report the development of an innovative standoff ultracompact micro-Raman instrument that would solve some of the limitations of traditional micro-Raman systems to provide a superior instrument for future NASA missions. This active remote sensor system, based on a 532 nm laser and a miniature spectrometer, is capable of inspection and identification of minerals, organics, and biogenic materials within several centimeters (2-20 cm) at a high 10 μm resolution. The sensor system is based on inelastic (Raman) light scattering and laser-induced fluorescence...
January 1, 2018: Applied Optics
Wei Hu, Xinrui Cao
Monitoring reaction paths is not only a fundamental scientific issue but also helps us to understand and optimize the catalytic process. Infrared (IR) and Raman spectroscopies are powerful tools for detecting particular molecules or intermediate products as a result of their ability to provide the molecular "finger-print". However, theoretical modeling for the vibrational spectra of molecular adsorbates on metallic surfaces is a long-standing challenge, because accurate descriptions of the electronic structure for both the metallic substrates and adsorbates are required...
January 10, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Christian Matthäus, Sebastian Dochow, Kokila D Egodage, Bernd F Romeike, Bernhard R Brehm, Jürgen Popp
Intravascular imaging techniques provide detailed specification about plaque appearance and morphology, but cannot deliver information about the biochemical composition of atherosclerotic plaques. As the biochemical composition is related to the plaque type, important aspects such as the risk of a plaque rupture and treatment are still difficult to assess. Currently, various spectroscopic techniques are tested for potential applications for the chemical analysis of plaque depositions. Here, we employ Raman spectroscopy in combination with optical coherence tomography (OCT) for the characterization of plaques on rabbits in vivo...
January 2018: Journal of Biomedical Optics
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