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Raman crystallinity

Tariq Fahmi, La Donna Branch, Zeid A Nima, Dae Song Jang, Alena V Savenka, Alexandru S Biris, Alexei G Basnakian
Graphene, a crystalline allotrope or carbon, presents numerous useful properties; however, its toxicity is yet to be determined. One of the most dramatic and irreversible toxic abilities of carbon nanomaterials is the induction of DNA fragmentation produced by endogenous cellular endonucleases. This study demonstrated that pristine graphene exposed to cultured kidney tubular epithelial cells is capable of inducing DNA fragmentation measured by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, which is usually associated with cell death...
May 24, 2017: Journal of Applied Toxicology: JAT
Xu Wang, Lin-Ying Du, Meng Du, Chao Ma, Jie Zeng, Chun-Jiang Jia, Rui Si
A low-concentration cobalt (∼6 at%) and manganese (∼3 at%) bimetallic oxide catalyst supported on ceria nanorods (CoMnOx/CeO2), as well as its related single metal oxide counterparts (CoOx/CeO2 and MnOx/CeO2) was synthesized via a deposition-precipitation approach. The fresh samples after air-calcination at 400 °C were tested under the reaction conditions of CO oxidation, and showed the following order of reactivity: CoMnOx/CeO2 > CoOx/CeO2 > MnOx/CeO2. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data identified that the structure of the CeO2 support was maintained during deposition of metal (Co, Mn) ions while the corresponding vis-Raman spectra verified that more oxygen vacancies were created after deposition-precipitation than those in pure ceria nanorods...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Ferenc Liebig, Radwan M Sarhan, Mathias Sander, Wouter A Koopman, Roman Schuetz, Matias Bargheer, Joachim Koetz
Anisotropic plasmonic particles such as gold nanotriangles have extraordinary structural, optical and physico-chemical properties. For many applications in different fields it is essential to prepare them in a chemically and physically stable, structurally well-defined manner, e.g., as large and uniform coverage on a substrate. We present a direct method for the large scale close-packed monolayer formation of edge-to-edge ordered, ultrathin crystalline gold nanotriangles on Si-wafers or quartz glass via the transfer of these asymmetric particles to the air-liquid interface after adding ethanol-toluene mixtures without any subsequent surface functionalization...
May 23, 2017: ACS Applied Materials & Interfaces
Sundar Kunwar, Puran Pandey, Mao Sui, Quanzhen Zhang, Ming-Yu Li, Jihoon Lee
Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model...
December 2017: Nanoscale Research Letters
G D Saraiva, J R Maia, J A Lima, C E S Nogueira, P T C Freire, F F de Sousa, A M R Teixeira, J Mendes Filho
This research reports a pressure dependent Raman study of the sorbic acid between 0.0 and 10.0GPa. The unpolarized Raman spectra were measured in the spectral range of 20-3000cm(-1). The high-pressure Raman scattering study of the sorbic acid showed that it underwent a gradual, disordering process. At the room temperature and at the ambient pressure conditions, the crystal structure of the sorbic acid belongs to the monoclinic system with a C2/c (C2h(6)) space group. The pressure increase induced a higher disorder in the monoclinic unit cell, since a single bending mode, and only very broad stretching Raman modes are present at pressure of ~10GPa...
May 10, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jian Liu, Hong Bi, Paulo Cesar Morais, Xiang Zhang, Fapei Zhang, Lin Hu
Room temperature magnetic ordering is reported for very small carbon dots (CDs), mat-like polyaniline nanofibers (Mat-PANI) and a composite of CDs@Mat-PANI containing 0.315 wt% CDs. We have found saturation magnetization (M S ) of CDs, Mat-PANI and CDs@Mat-PANI at 5 (20/300) K equals to 0.0079 (0.0048/0.0019), 0.0116 (0.0065/0.0055) and 0.0349 (0.0085/0.0077) emu/g, respectively. The M S enhancement in CDs@Mat-PANI (200% and 40% at 5 K and 300 K, respectively) is attributed to electron transfer from Mat-PANI imine N-atoms to the encapsulated CDs...
May 19, 2017: Scientific Reports
M L Mei, F Nudelman, B Marzec, J M Walker, E C M Lo, A W Walls, C H Chu
Silver diamine fluoride (SDF) is found to promote remineralization and harden the carious lesion. Hydroxyapatite crystallization is a crucial process in remineralization; however, the role of SDF in crystal formation is unknown. We designed an in vitro experiment with calcium phosphate with different SDF concentrations (0.38, 1.52, 2.66, 3.80 mg/mL) to investigate the effect of this additive on the nucleation and growth of apatite crystals. Two control groups were also prepared-calcium phosphate (CaCl2·2H2O + K2HPO4 in buffer solution) and SDF (Ag[NH3]2F in buffer solution)...
May 1, 2017: Journal of Dental Research
Stella Corsetti, Thomas Rabl, David McGloin, Johannes Kiefer
The solid to liquid phase transition of n-alkanes with more than ten carbon atoms is an interesting phenomenon relevant to many fields, from cosmetics to automotive. Here we report Raman spectroscopy of tetradecane, pentadecane and hexadecane as a function of temperature. In order to gain information on the structural changes that the hydrocarbons undergo during melting, and to determine the temperature and the speed at which the phase change occurs, their temperature-dependent Raman spectra are acquired. The spectra are analysed not only with respect to frequency shifts, band widths, and intensity ratio of certain bands, but also using a principal component analysis...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Liqing Wei, Umesh P Agarwal, Kolby C Hirth, Laurent M Matuana, Ronald C Sabo, Nicole M Stark
Cellulose nanocrystals (CNCs), produced from dissolving wood pulp, were chemically functionalized by transesterification with canola oil fatty acid methyl ester (CME). CME performs as both the reaction reagent and solvent. Transesterified CNC (CNCFE) was characterized for their chemical structure, morphology, crystalline structure, thermal stability, and hydrophobicity. Analysis by Fourier transform infrared (FTIR) and FT-Raman spectroscopies showed that the long chain hydrocarbon structure was successfully grafted onto CNC surfaces...
August 1, 2017: Carbohydrate Polymers
Sundrarajan M, Bama K, Bhavani M, Jegatheeswaran S, Ambika S, Sangili A, Nithya P, Sumathi R
In this work, we synthesized titanium dioxide (TiO2) nanoparticles using leaf extract of Morinda citrifolia (M. citrifolia) by the advanced hydrothermal method. The synthesized TiO2 nanoparticles were characterized by X-ray diffraction (XRD), Fourier transmission infrared (FT-IR), Ultraviolet-visible diffuse reflectance (UV-Vis DRS), Ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM with EDX) techniques. The XRD major peak at 27...
May 3, 2017: Journal of Photochemistry and Photobiology. B, Biology
Shradhanjali Sahoo, T R Ravindran, Sharat Chandra, R M Sarguna, B K Das, T N Sairam, V Sivasubramanian, C Thirmal, P Murugavel
Diisopropylammonium bromide (DIPAB) can be crystallized either in an orthorhombic (P212121) or in a monoclinic (P21) structure at room temperature depending on synthesis conditions. The non-polar orthorhombic structure exhibits a subtle, irreversible transformation into the ferroelectric monoclinic-II (m-II) phase above ~421K. At a slightly higher temperature of 426K this m-II (P21) phase reversibly transforms into a disordered, paraelectric monoclinic-I (P21/m) structure. We synthesized DIPAB in the orthorhombic structure, heated it to obtain the m-II phase and carried out a systematic study of their Raman and IR spectra...
May 5, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Mario Santoro, Federico A Gorelli, Roberto Bini, Julien Haines
Molecular nitrogen is a benchmark system for condensed matter and, in particular, for looking at universal properties of strongly confined dense systems. We conducted Raman and X-ray diffraction measurements on a dense and disordered form of molecular nitrogen subnanoconfined in a noncatalytic pure SiO2 zeolite under pressure, up to 50 GPa. In this form, N2-N2 interactions and, consequently, distances are found to be very close to those of bulk N2 and intramolecular interactions progressively weaken upon increasing pressure...
May 15, 2017: Journal of Physical Chemistry Letters
Inho Nam, Jongseok Park, Soomin Park, Seongjun Bae, Young Geun Yoo, Jeong Woo Han, Jongheop Yi
Real-time analysis of changes in the atomic environment of materials is a cutting edge technology that is being used to explain reaction dynamics in many fields of science. Previously, this kind of analysis was only possible using heavy nucleonic equipment such as XANES and EXAFS, or Raman spectroscopy on a moderate scale. Here, a new methodology is described that can be used to track changes in crystalline developments during complex Li insertion reactions via the observation of structural color. To be specific, the changes in atomic crystalline and nanostructure are shown during Li insertion in a complex TiO2 polymorph...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Arjun Kalra, Patrick Tishmack, Joseph W Lubach, Eric J Munson, Lynne S Taylor, Stephen R Byrn, Tonglei Li
Despite numerous challenges in their theoretical description and practical implementation, amorphous drugs are of growing importance to the pharmaceutical industry. One such challenge is to gain molecular level understanding of the propensity of a molecule to form and remain as a glassy solid. In this study, a series of structurally similar diarylamine compounds was examined to elucidate the role of supramolecular aggregation on crystallization kinetics from supercooled liquid state. The structural similarity of the compounds makes it easier to isolate the molecular features that affect crystallization kinetics and glass forming ability of these compounds...
May 17, 2017: Molecular Pharmaceutics
Isao Noda, Anjan Roy, James Carriere, Brian J Sobieski, D Bruce Chase, John F Rabolt
Two-dimensional correlation analysis was applied to the time-dependent evolution of Raman spectra during the isothermal crystallization of bioplastic, poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] or PHBHx copolymer. Simultaneous Raman measurement of both carbonyl stretching and low-frequency crystalline lattice mode regions made it possible to carry out the highly informative hetero-mode correlation analysis. The crystallization process of PHBHx involves: (1) the early nucleation stage; (2) the primary growth of well-ordered crystals of PHBHx; and (3) the secondary crystal growth phase...
January 1, 2017: Applied Spectroscopy
S Türk, I Altınsoy, G ÇelebiEfe, M Ipek, M Özacar, C Bindal
In this study, some properties of biomimetic synthesized hydroxyapatite by using different sources of calcium were investigated. Biomimetic synthesis of hydroxyapatite was carried out in microwave oven using 1.5 simulated body fluid (SBF) solution having different calcium sources with 800W power for 15min. As phosphorus source di-ammonium hydrogen phosphate ((NH4)2HPO4) while for each sample as a calcium sources calcium chloride (CaCl2), calcium nitrate tetra hydrate (Ca(NO3)2·4H2O) and calcium hydroxide (Ca(OH)2) were utilized, respectively...
July 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Yannick Guinet, Laurent Paccou, Florence Danède, Patrick Derollez, Alain Hédoux
Valsartan is an antihypertensive drug, recognized to be marketed in an amorphous state, different from that obtained by quenching the liquid state below Tg. This is an unusual and very original situation, given that the amorphous state is unstable. Low-wavenumber Raman spectroscopy and X-ray diffraction investigations were carried out on the various solid-state forms of valsartan. It was found that the marketed form is not amorphous and can be described in terms of mesophase in which the long-range order of the stable crystal is limited on the lengthscale of tens nanometers, inducing a melting temperature lower than that of the stable crystalline state, inherent to the crystallite size...
May 1, 2017: International Journal of Pharmaceutics
Alessio Petrone, David B Williams-Young, David B Lingerfelt, Xiaosong Li
Time-resolved Raman spectroscopy has proven useful for studying the formation of polarons in conjugated polymers, verifying the presence of reactive intermediates in photochemical reactions, investigating nonradiative transitions in the short lifetime of the photoexcited species, and resolving electron-phonon coupling strengths and exciton dissociation in crystalline materials. In this paper, we present an excited state transient Raman analysis protocol combining ab initio direct molecular dynamics, transient excited state Hessian, and excited state nonresonant Raman activities evaluations...
May 12, 2017: Journal of Physical Chemistry. A
Barbara Hachuła, Anna Polasz, Maria Książek, Joachim Kusz, Oliwia Starczewska, Wojciech Pisarski
The polarized IR spectra of isotopically neat and isotopically substituted monocrystalline samples of 2-phenyl-1H-imidazole (2PI) and 4-phenyl-1H-imidazole (4PI) were recorded at two temperatures of 293 K and 77 K. The room-temperature ATR-FTIR and Raman spectra of 2PI and two polymorphic forms of 4PI were also recorded. Theoretical analysis of the vibrational spectra of selected imidazole derivatives reflected similar characteristics of their hydrogen-bond networks and allowed us to obtain the information about the mechanism of the H/D isotopic "self-organization" phenomenon...
April 24, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
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...
May 11, 2017: Nanoscale
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