Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Structural and Antimicrobial Studies of Coordination Compounds of Phenylalanine and Glycine  [cached]
Temitayo Olufunmilayo Aiyelabola,Ojo Isaac,Akinkunmi Olugbenga
International Journal of Chemistry , 2012, DOI: 10.5539/ijc.v4n2p49
Abstract: Coordination compounds of glycine and phenylalanine were synthesized, characterized using electronic and infrared spectroscopy, magnetic susceptibility measurement and mass spectrometry. The ligands coordinated to the metal in a bidentate fashion using N and O donor atoms. Square planar geometry is proposed for the Mn(II), Co(II), Ni(II) and Cu(II) complexes based on the results obtained from their characterization. Tetrahedral geometry is however proposed the Cd(II) complexes. The in-vitro biological effect of the synthesized compounds was investigated. The compounds were tested against three gram-negative bacteria, E.coli, P. aeruginosa, P. vulgaris, three gram positive bactria, S. aureus, B. subtilis, MRSA and a fungus C. Albicans. A comparative study of the zones of inhibition observed for the ligand and coordinated synthesized compounds indicated that the synthesized compounds, in some cases, showed higher zones of inhibition than that of the free ligands. It is therefore suggested that increasing the number of chelate rings may increase the lipophilicity of the coordinated complex and therefore its antimicrobial activity.
Studies on Structural, Spectral, and Optical Properties of Organic Nonlinear Optical Single Crystal: 2-Amino-4,6-dimethylpyrimidinium p-Hydroxybenzoate  [PDF]
S. Sudhahar,M. Krishna Kumar,A. Silambarasan,R. Muralidharan,R. Mohan Kumar
Journal of Materials , 2013, DOI: 10.1155/2013/539312
Abstract: 2-Amino-4,6-dimethylpyrimidinium p-hydroxybenzoate (ADPHB), a novel organic material, was synthesized, and crystals were grown by slow evaporation solution growth method. The cell parameters and crystalline perfection of the grown crystal were studied by single crystal and powder X-ray diffraction analyses. The presence of various functional groups of the grown crystal was confirmed using Fourier Transform infrared spectral analysis. UV-Visible spectrum shows that ADPHB crystals have high transmittance in the range 305–900?nm. The refractive index and transient photoluminescence properties of the grown crystal were analyzed. The laser induced surface damage threshold, optical birefringence, and second harmonic generation efficiency of the grown crystal were studied. 1. Introduction The research on new organic nonlinear optical (NLO) materials has attracted more research groups to them for their advantages over the inorganic nonlinear optical materials. The organic nonlinear optical molecules generally have a larger second-order nonlinear optical coefficient, and hence they are widely used in many applications such as optical communication, information storage, and optical switching [1–5]. The continuous research on organic NLO materials prompted to find many new nonlinear optical complexes engineered by organic molecules. For instance, nonlinear optical complexes formed from pyridine and carboxylic acids have been crystallized, and the structural, optical, and thermal properties of these crystals have been investigated due to their significant impact on laser technology, optical communication, and optical data storage technology [6]. Organic nonlinear optical compounds have large macroscopic second-order NLO susceptibilities , low dielectric dispersion, and ultrafast response to external electric fields [7, 8]. Organic nonlinear optical materials are formed based on NLO chromophores, which should be oriented in noncentrosymmetric way in order to exhibit macroscopic second-order nonlinear optical response. There are several different strategies resulting in macroscopic organic materials, including ferroelectric liquid crystals [9], self-assembled films [10], Langmuir-Blodgett films [11], and poled polymer films [12], as well as single crystals [13]. Among them, polar organic crystals are of special interest, since large NLO effect can be achieved due to the high density of chromophores in the crystals, as well as the most stable packing of chromophores in macroscopic materials, resulting in a superior photochemical and thermal stability as compared with
Structural, Electrical and Optical Characterization Studies on Glycine Picrate Single Crystal : A Third Order Nonlinear Optical Material  [PDF]
T. Uma Devi, N. Lawrence, R. Ramesh Babu, K. Ramamurthi, G. Bhagavannarayana
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2009, DOI: 10.4236/jmmce.2009.810065
Abstract: Single crystal of an organic nonlinear optical (NLO) material, Glycine picrate (GP), was grown by slow cooling method. The structural perfection of the grown crystal was analyzed by highresolution X-ray diffraction (rocking curve) measurements. UV-Visible-NIR spectral analysis was used to determine the optical constants and band gap of GP. The nature of variation of dielectric constant with frequency at different temperatures was investigated. Third-order optical nonlinearities of GP crystal were investigated. Etch patterns of the grown crystal quality were studied.
Structural and Optical Characterization Studies on 2, 4- dinitrophenylhydrazine Single Crystal  [PDF]
T. Uma Devi, N. Lawrence, R. Ramesh Babu, K. Ramamurthi, G. Bhagavannarayana
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.94023
Abstract: Single crystal of an organic nonlinear optical (NLO) material, 2,4-Dnitrophenylhydrazine (DNPH), was grown by slow cooling method. Powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) FT-Raman and NMR studies have confirmed respectively the crystal structure and functional groups of the grown crystal. Crystalline perfection of single crystals was evaluated by high resolution X-ray diffractometry (HRXRD) using a multicrystal X–ray diffractometer and found that the grown crystals are nearly perfect. UV-Visible-NIR spectral analysis was used to determine the optical constants and band gap of DNPH. Fluorescence spectrum of DNPH was recorded.
Studies On The Growth And Characteristics Of Structural And Photoconductivity Of Bis Glycine Maleate Single Crystal  [PDF]
V. J. Priyadharshini And G. Meenakshi
Golden Research Thoughts , 2013, DOI: 10.9780/22315063
Abstract: A single crystal of Bis glycine maleate has been grown from aqueous solution by slow evaporationmethod by optimizing the growth parameters within a period of 45 days. From the x-ray diffraction the crystal wasfound to be crystallize in hexagonal structure with a=7.402 , b=7.04 , c= 5.48 and á=a=90°, =120°. Thefunctional group was confirmed in FTIR analysis. The UV-Vis spectral analysis has revealed the absence of highabsorption region between 200 to 800nm. The optical band gap was calculated and found to be 4.06 eV. Thephotoconductivity study confirmed that it is a positive photoconductivity
The Structural Dilemma of Bulk Polyethylene: An Intermediary Structure  [PDF]
Morteza Laridjani, Pierre Leboucher
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006228
Abstract: Background The Fourier space (reciprocal space) image of bulk polyethylene consists of lines superimposed on the coherent diffuse background. The mixed character of the image indicates the complex nature of these compounds. The inability in detecting full images of reciprocal space of polymeric substances without Compton radiation and the other undesirable diffuse scatterings has misled the structural analysis (structural characterisation) of these materials. Principal Findings We propose the use of anomalous diffractometry where, it is possible to obtain a real image of reciprocal space without Compton radiation and other undesirable scatterings. By using classical diffractometry techniques this procedure is not possible. This methodology permitted us to obtain the “Direct Delta function”, in the case of polycrystalline substances that was not previously detected. A new procedure was proposed to interpret the image of reciprocal space of bulk polyethylene. The results show the predominance of the geometry of local order determination compared to the crystal unit cell. The analysis of x-ray diffraction images illustrates that the elementary structural unit is a tetrahedron. This structural unit illustrates the atoms in the network scatter in a coherent diffuse manner. Moreover, the interference function derived from the coherent diffuse scattering dampens out quickly and the degree of randomness is superior to a liquid state. The radial distribution function derived from this interference function shows bond shortening in the tetrahedron configuration. It is this particular effect, which stabilises polyethylene. Conclusion Here we show by anomalous diffractometry that the traditional concept of the two-phase or the crystal-defect model is an oversimplification of the complex reality. The exploitation of anomalous diffractometry has illustrated that polyethylene has an intermediate ordered structure.
Crystal, Solution and In silico Structural Studies of Dihydrodipicolinate Synthase from the Common Grapevine  [PDF]
Sarah C. Atkinson, Con Dogovski, Matthew T. Downton, F. Grant Pearce, Cyril F. Reboul, Ashley M. Buckle, Juliet A. Gerrard, Renwick C. J. Dobson, John Wagner, Matthew A. Perugini
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038318
Abstract: Dihydrodipicolinate synthase (DHDPS) catalyzes the rate limiting step in lysine biosynthesis in bacteria and plants. The structure of DHDPS has been determined from several bacterial species and shown in most cases to form a homotetramer or dimer of dimers. However, only one plant DHDPS structure has been determined to date from the wild tobacco species, Nicotiana sylvestris (Blickling et al. (1997) J. Mol. Biol. 274, 608–621). Whilst N. sylvestris DHDPS also forms a homotetramer, the plant enzyme adopts a ‘back-to-back’ dimer of dimers compared to the ‘head-to-head’ architecture observed for bacterial DHDPS tetramers. This raises the question of whether the alternative quaternary architecture observed for N. sylvestris DHDPS is common to all plant DHDPS enzymes. Here, we describe the structure of DHDPS from the grapevine plant, Vitis vinifera, and show using analytical ultracentrifugation, small-angle X-ray scattering and X-ray crystallography that V. vinifera DHDPS forms a ‘back-to-back’ homotetramer, consistent with N. sylvestris DHDPS. This study is the first to demonstrate using both crystal and solution state measurements that DHDPS from the grapevine plant adopts an alternative tetrameric architecture to the bacterial form, which is important for optimizing protein dynamics as suggested by molecular dynamics simulations reported in this study.
Structural, electronic and optical characterization of bulk platinum nitrides: a first-principles study  [PDF]
Mohammed S. H. Suleiman,Daniel P. Joubert
Physics , 2013,
Abstract: We present a detailed quantum mechanical non empirical DFT investigation of the energy-optimized geometries, phase stabilities and electronic properties of bulk Pt3N, PtN and PtN2 in a set of twenty different crystal structures. Structural preferences for these three stoichiometries were analyzed and equilibrium structural parameters were determined. We carefully investigated the band-structure and density of states of the relatively most stable phases. Further, GW_0 calculations within the random-phase approximation (RPA) to the dielectric tensor were carried out to derive their frequency-dependent optical constants of the most likely candidates for the true crystal structure. Obtained results were comprehensively compared to previous calculations and to experimental data.
Gauging Structural Aspects of ZnO nano-Crystal Growth ThroughX-ray Diffraction Studies and PAC  [PDF]
Bichitra Nandi Ganguly,Sreetama Dutta,Soma Roy,Jens R?der,Karl Johnston,ISOLDE-Collaboration
Physics , 2013,
Abstract: The structural characterization of sol-gel based nano crystalline ZnO material is being reported as we observe several previously unreported structural aspects following a sequence of annealing stages. As-grown samples were characterised by Fourier Transform Infrared Spectroscopy (FTIR). Chemical purity of the nano-grains and their crystallinity has been monitored by energy dispersive X-ray (EDAX) analysis and transmission electron microscopy (TEM), while the unusual changes in nano-crystal growth structure have been studied by X-ray diffraction method. In addition, such samples have been studied by using perturbed angular correlation (PAC) technique with the short-lived radioactive probe 111mCd. Changes in the local electronic environment following sintering of the nano-crystalline grains have been observed by this method.
Iron pnictides: Single crystal growth and effect of doping on structural, transport and magnetic properties  [PDF]
G. L. Sun,D. L. Sun,M. Konuma,P. Popovich,A. Boris,J. B. Peng,K. -Y. Choi,P. Lemmens,C. T. Lin
Physics , 2009, DOI: 10.1007/s10948-010-1123-z
Abstract: We demonstrate the preparation of large, free standing iron pnictide single crystals with a size up to 20 x 10 x 1 mm3 using solvents in zirconia crucibles under argon atmosphere. Transport and magnetic properties are investigated to study the effect of potassium doping on the structural and superconducting property of the compounds. The spin density wave (SDW) anomaly at Ts ~138 K in BaFe2As2 single crystals from self-flux shifts to Ts ~85 K due to Sn solvent growth. We show direct evidence for an incorporation of Sn on the Fe site. The electrical resistivity data show a sharp superconducting transition temperature Tc~38.5 K for the single crystal of Ba0.68K0.32Fe2As2. A nearly 100% shielding fraction and bulk nature of the superconductivity for the single crystal were confirmed by magnetic susceptibility data. A sharp transition Tc~25 K occurred for the single crystal of Sr0.85K0.15Fe2As2. There is direct evidence for a coexistence of the SDW and superconductivity in the low doping regime of Sr1-xKxFe2As2 single crystals. Structural implications of the doping effects as well as the coexistence of the two order parameters are discussed.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.