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Raman crystallinity

I Georgieva, N Trendafilova, N Dodoff, D Kovacheva
DFT and periodic-DFT (PAW-PBE method, code VASP) calculations have been performed to study the structural and vibrational characteristics of cis-diamminedichloroplatinum(II) (cisplatin) at molecular and outside molecular level. To estimate the effect of the intermolecular interactions in crystal on the structural and vibrational properties of cisplatin, three theoretical models are considered in the present study: monomer (isolated molecule), hydrogen bonded dimer and periodic solid state structures. The work focused on the role of the theoretical models for correct modeling and prediction of geometrical and vibrational parameters of cisplatin...
January 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Ying Jin, Anthony P Kotula, Angela R Hight Walker, Kalman B Migler, Young Jong Lee
We use moving-window two-dimensional correlation spectroscopy (MW-2DCOS) for phase-specific Raman analysis of the n-alkane (C21H44) during melting from the crystalline solid phase to the intermediate rotator phase and to the amorphous molten phase. In MW-2DCOS, individual peak-to-peak correlation analysis within a small subset of spectra provides both temperature-resolved and spectrally disentangled Raman assignments conducive to understanding phase-specific molecular interactions and chain configurations. We demonstrate that autocorrelation MW-2DCOS can determine the phase transition temperatures with a higher resolving power than commonly-used analysis methods including individual peak intensity analysis or principal component analysis...
November 2016: Journal of Raman Spectroscopy: JRS
Amine Mezni, Tariq Altalhi, Nesrine Ben Saber, Ali Aldalbahi, Seifeddine Boulehmi, Abel Santos, Dusan Losic
This work aims at introducing the synthesis process of carbon nanotubes (CNTs) inside nanoporous anodic alumina (NAA) templates adopting a catalyst-free chemical vapor deposition (CVD) approach under different conditions. The nanotubular structure of NAA is prepared according to tow-step anodization process. This provides a unique platform to grow CNTs with precisely controlled geometric features. The structural features, crystalline structures and chemical composition of the resulting CNTs-NAA composites were systematically characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) as well as Raman spectroscopy...
December 19, 2016: Journal of Colloid and Interface Science
Barbara Bellich, Silvia Di Fonzo, Letizia Tavagnacco, Marco Paolantoni, Claudio Masciovecchio, Federica Bertolotti, Giovanna Giannini, Rita De Zorzi, Silvano Geremia, Alessandro Maiocchi, Fulvio Uggeri, Norberto Masciocchi, Attilio Cesàro
The phenomenon of polymorphism is of great relevance in pharmaceutics, since different polymorphs have different physicochemical properties, e.g., solubility, hence, bioavailability. Coupling diffractometric and spectroscopic experiments with thermodynamic analysis and computational work opens to a methodological approach which provides information on both structure and dynamics in the solid as well as in solution. The present work reports on the conformational changes in crystalline iopamidol, which is characterized by atropisomerism, a phenomenon that influences both the solution properties and the distinct crystal phases...
January 18, 2017: Molecular Pharmaceutics
Bilal Ahmed, Sumeet Kumar, Animesh K Ojha, P Donfack, A Materny
In this work, we have performed a facile and controlled synthesis of WO3 nanorods and sheets in different crystal phases (triclinic, orthorhombic and monoclinic) of WO3 using the sol-gel method. The detailed structures of the synthesized materials were examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy measurements. The shapes and crystal phases of the WO3 nanostructures were found to be highly dependent on the calcination temperature. The variation in crystalline phases and shapes is modified the electronic structure of the samples, which causes a variation in the value of optical band gap...
November 28, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Eunjin Kwon, Jineun Kim, Kang Yeol Lee, Tae Ho Kim
A copper(I) coordination polymer, [Cu2I2L2]n (CP 1), shows luminescence mechanochromism with a color change from greenish-blue to yellow upon the application of pressure. Powder X-ray diffraction and Raman studies reveal that the changes in the bond lengths in crystalline CP 1 are the main cause of luminescence mechanochromism. The luminescence mechanochromic process of CP 1 preserves its crystallinity with a small lattice distortion, despite very high pressure, and it is a non-phase-transition process. After the addition of several drops of acetonitrile to the ground and compressed samples, the original greenish-blue emissive and crystalline states are restored...
December 29, 2016: Inorganic Chemistry
M B Sreedhara, Jay Ghatak, B Bharath, Chintamani Nagesa Ramachandra Rao
Ultrathin epitaxial films (10 to 90 nm thick) of V2O5 have been grown on c-Al2O3 by atomic layer deposition using vanadyl acetylacetonate as the vanadium precursor along with oxygen plasma. Various process parameters have been optimised for the purpose, and excellent crystalline films could be obtained below 200 °C, with out the need for post-heat treatment. With a moderate temperature window, the process yields a growth rate of 0.45 Å /cycle. The films have been characterized by electron microscopy, atomic force microscopy, Raman spectroscopy and other means...
December 29, 2016: ACS Applied Materials & Interfaces
Ki-Jae Jeong, Younseong Song, Hye-Ri Shin, Ji Eun Kim, Jeonghyo Kim, Fangfang Sun, Dae-Youn Hwang, Jaebeom Lee
Chitosan, produced from chitin, is one of the polymers with promising applications in various fields. However, despite diverse research studies conducted on its biocompatibility, its uses are still limited. The main reason is the degree of deacetylation (DOD), which represents the proportion of deacetylated units in the polymer and is directly correlated with its biocompatibility property. In this article, the in vivo biocompatibility of three chitosan-hydroxyapatite composite films composed of chitosan with different DOD values was investigated by traditional biological protocols and novel optical spectroscopic analyses...
December 29, 2016: Journal of Biomedical Materials Research. Part A
Shanti Swaroop Srivastava, Aditya Anand Jamkhindikar, Rajeev Raman, Maroor K Jobby, Swathi Chadalawada, Rajan Sankaranarayanan, Yogendra Sharma
βγ-Crystallins are important constituents of the vertebrate eye lens, whereas in microbes, they are prevalent as Ca(2+)-binding proteins. In archaea, βγ-crystallins are conspicuously confined to two methanogens, viz., Methanosaeta and Methanosarcina. One of these, i.e., M-crystallin from Methanosarcina acetivorans, has been shown to be a typical Ca(2+)-binding βγ-crystallin. Here, with the aid of a high-resolution crystal structure and isothermal titration calorimetry, we report that "Methallin", a βγ-crystallin from Methanosaeta thermophila, is a trimeric, transition metal-binding protein...
January 18, 2017: Biochemistry
Yangxi Chu, Chak K Chan
Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy...
December 27, 2016: Journal of Physical Chemistry. A
I S Yahia, Mohd Shkir, S AlFaify, V Ganesh, H Y Zahran, Mona Kilany
In this work, the authors have fabricated the nanorods and nanosheets of pure and Te-doped HAp with different Te concentrations (0.04, 0.08, 0.16, 0.24wt%) by microwave-assisted technique at low temperature. The crystallite size, degree of crystallinity and lattice parameters are calculated. FE-SEM study confirms that the fabricated nanostructures are nanorods of diameter about 10nm in undoped and at low concentration of Te doping. However, at and higher concentration, it becomes nanosheets of about 5nm thickness...
March 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Torbjörn Björkman, Viera Skakalova, Simon Kurasch, Ute Kaiser, Jannik C Meyer, Jurgen H Smet, Arkady V Krasheninnikov
Kagome lattices are structures possessing fascinating magnetic and vibrational properties, but in spite of a large body of theoretical work, experimental realizations and investigations of their dynamics are scarce. Using a combination of Raman spectroscopy and density functional theory calculations, we study the vibrational properties of two-dimensional silica (2D-SiO2), which has a kagome lattice structure. We identify the signatures of crystalline and amorphous 2D-SiO2 structures in Raman spectra and show that, at finite temperatures, the stability of 2D-SiO2 lattice is strongly influenced by phonon-phonon interaction...
December 27, 2016: ACS Nano
Gwangwoo Kim, Minsu Kim, Chohee Hyun, Seokmo Hong, Kyung Yeol Ma, Hyeon Suk Shin, Hyunseob Lim
We report on an insulating two-dimensional material, hexagonal boron nitride (h-BN), which can be used as an effective wrapping layer for surface-enhanced Raman spectroscopy (SERS) substrates. This material exhibits outstanding characteristics such as its crystallinity, impermeability, and thermal conductance. Improved SERS sensitivity is confirmed for Au substrates wrapped with h-BN, the mechanism of which is investigated via h-BN thickness-dependent experiments combined with theoretical simulations. The investigations reveal that a stronger electromagnetic field can be generated at the narrowed gap of the h-BN surface, which results in higher Raman sensitivity...
December 27, 2016: ACS Nano
I G Batyrev
The formation of nitrogen-hydrogen networked compounds is a promising approach for obtaining high energy density materials. Multiple experimental reports indicate that the synthesis pressure and temperature of high-energy nitrogen networked compounds significantly decrease when adding hydrogen to nitrogen. One- and two-dimensional structures of nitrogen-hydrogen mixtures are reported to form during synthesis and have also been observed with simulations; however, the structures are not thoroughly established or well understood...
January 13, 2017: Journal of Physical Chemistry. A
Mahshid Ahmadi, Stevin S Pramana, Chris Boothroyd, Yeng Ming Lam
The performance of solar cells fabricated using Cu(In,Ga)(S,Se)2 nanocrystal (NC) inks synthesized using the hot injection method has yielded efficiencies up to 12% recently. The efficiency of these devices is highly dependent on the chemical composition and crystallographic quality of the NCs. The former has been extensively discussed as it can be easily correlated to the optical properties of the film, but detailed crystallographic structure of these NCs has scarcely been discussed and it can influence both the optical and electrical properties...
January 27, 2017: Nanotechnology
He Zhang, Adam S Hock
Crystalline tungsten disulfide (WS2) has been prepared from the reaction of bis(cyclopentadienyl)tungsten dihydride with sulfur at room temperature and ambient pressure in organic solvents. WS2 was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, resonance Raman spectroscopy, transmission electron microscopy, and X-ray absorption spectroscopy, and the resulting WS2 is highly crystalline by X-ray diffraction. The low-temperature synthesis is hypothesized to be a result of highly mobile surface W-Cp groups that are able to facilitate crystallization...
January 3, 2017: Inorganic Chemistry
Xiaolong Zhang, Kun Li, Wenyu Shi, Caihua Wei, Xiaoping Song, Sen Yang, Zhanbo Sun
Baize-like monolithic CeO2 and NiO/CeO2 nanorod catalysts were prepared by combined dealloying and calcination and the catalytic activities were evaluated using CO catalytic oxidation. The CeO2 catalysts were composed of nanorods and exhibited a three-dimensional supporting structure with pores. After introduction of NiO, dispersed NiO nanosheets and nanoparticles were supported on the surface of CeO2 nanorods and they were not well-crystallined due to CeO2 inhibiting the NiO crystallization. The Raman and x-ray photoelectron spectroscopy analyses revealed that the introduction of NiO species into CeO2 generated more coordinate unsaturated Ni atoms, oxygen vacancies, defects and active sites for CO catalytic reactions...
January 27, 2017: Nanotechnology
Supriya Das, Uttam Pal, Moumita Chatterjee, Sumit Kumar Pramanik, Biswadip Banerji, Nakul C Maiti
The proline residue in a protein sequence generates constraints to its secondary structure as the associated torsion angles become a part of the heterocyclic ring. It becomes more significant when two consecutive proline residues link via amide linkage and produce additional configurational constraint to a protein's folding and stability. In the current manuscript we have illustrated conformation preference of a novel dipeptide, (R)-tert-butyl 2-((S)-2-(methoxycarbonyl)pyrrolidine-1-carbonyl)pyrrolidine-1-carboxylate...
December 15, 2016: Journal of Physical Chemistry. A
Busolo Wa Wabuyele, Sutthilug Sotthivirat, George X Zhou, Jason Ash, Sundeep S Dhareshwar
Process-induced inadvertent phase change of an active pharmaceutical ingredient in a drug product could impact chemical stability, physical stability, shelf life, and bioperformance. In this study, dispersive Raman spectroscopy is presented as an alternative method for the nondestructive, high-throughput, at-line quantification of amorphous conversion. A quantitative Raman method was developed using a multivariate partial least squares (PLS) regression calibration technique with solid-state nuclear magnetic resonance (ssNMR) spectroscopy as the reference method...
February 2017: Journal of Pharmaceutical Sciences
Zhongfeng Tang, Junjie Bao, Qingxia Du, Yu Shao, Minghao Gao, Bangkun Zou, Chunhua Chen
A complete and ordered layered structure on the surface of LiNi0.815Co0.15Al0.035O2 (NCA) has been achieved via a facile surface-oxidation method with Na2S2O8. The field-emission transmission electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH)2 into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni(2+) and Co(2+) ions are reduced with preoxidization on the surface of the hydroxide precursor...
December 21, 2016: ACS Applied Materials & Interfaces
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