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181.
Gurinder Singh Aman Kaura Monika Mukul Janpreet Singh S. K. Tripathi 《Applied Physics A: Materials Science & Processing》2014,117(3):1307-1314
We have carried out comprehensive computational and experimental study on the face-centered cubic Ge2Sb2Te5 (GST) and indium (In)-doped GST phase change materials. Structural calculations, total density of states and crystal orbital Hamilton population have been calculated using first-principle calculation. 5 at.% doping of In weakens the Ge–Te, Sb–Te and Te–Te bond lengths. In element substitutes Sb to form In–Te-like structure in the GST system. In–Te has a weaker bond strength compared with the Sb–Te bond. However, both GST and doped alloy remain in rock salt structure. It is more favorable to replace Sb with In than with any other atomic position. X-ray diffraction (XRD) analysis has been carried out on thin film of In-doped GST phase change materials. XRD graph reveals that In-doped phase change materials have rock salt structure with the formation of In2Te3 crystallites in the material. Temperature dependence of impedance spectra has been calculated for thin films of GST and doped material. Thickness of the as-deposited films is calculated from Swanepoel method. Absorption coefficient (α) has been calculated for amorphous and crystalline thin films of the alloys. The optical gap (indirect band gap) energy of the amorphous and crystalline thin films has also been calculated by the equation \( \alpha h\nu = \beta (h\nu - E_{\text{g }} )^{2} \) . Optical contrast (C) of pure and doped phase change materials have also been calculated. Sufficient optical contrast has been found for pure and doped phase change materials. 相似文献
182.
Some mononuclear mixed-carboxylato ??-diketonato oxovanadium(IV) complexes of the general formula [VO(??-dike)(RCOO)] (where H??-dike?=?acetylacetone; benzoylacetone or dibenzoylmethane, R?=?C15H31 or C17H35) have been synthesized from VO(acac)2 by stepwise substitutions of acetylacetonate ion with straight chain fatty acids (RCOOH) and ??-diketones in p-xylene under reflux. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. These were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, 1H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance values indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of ??-diketonate and carboxylate ligands in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with 51V nucleus (I?=?7/2). Cyclic voltammograms of all the complexes displayed one-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Powder XRD and transmission electron microscopy (TEM) studies indicated the particles of these were lying in the nano-size range. The synthesized complexes are a new type of mixed-ligand complexes in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes. 相似文献
183.
WR Heinson CM Sorensen A Chakrabarti 《Langmuir : the ACS journal of surfaces and colloids》2012,28(31):11337-11342
Stimulated by experiments, we have carried out detailed simulations of aggregation in the presence of shear in a model colloidal system with a short-range attractive potential. For weak shear rates, we find that the shear enhanced the aggregation and that the long-time state of the system is independent of the shear history. For strong shear rates, precipitous fragmentation occurred after the shear was turned on and, after an induction period, the aggregation quickly rebounded in a stochastic manner similar to classical nucleation phenomena. However, the long-time state of the system is, once again, independent of the shear history. Thus, for both weak and strong shear cases, the shear rate acts as a state variable of the aggregating system. Shear rates employed in the simulations can be attained in laboratory experiments, as confirmed by computing the dimensionless Péclet numbers. 相似文献
184.
CS Tripathi P Losada-Pérez J Leys G Cordoyiannis C Glorieux J Thoen 《The European physical journal. E, Soft matter》2012,35(7):54-7
The high-resolution adiabatic scanning calorimetric technique has been used to investigate the nematic-smectic A transition (N-SmA in binary mixtures of the non-smectogenic liquid crystal heptyloxycyanobiphenyl (7OCB) and heptane, exhibiting a so-called injected smectic A phase. With the exception of a mixture with the lowest heptane mole fraction for which only an upper limit of 0.2 ± 0.2 J kg(-1) for a possible latent heat could be obtained, for all other mixtures finite latent heats were obtained. The mole fraction dependence of the latent heat could be well fitted with a crossover function consistent with a mean-field free energy expression with a non-zero cubic term arising from the Halperin-Lubensky-Ma (HLM) coupling between the SmA order parameter and the orientational director fluctuations. The mole fraction dependence of the heat capacity effective critical exponents is similar to that observed in mixtures of the two liquid crystals octyloxycyanobiphenyl (8OCB) and nonylcyanobiphenyl (9OCB). The thermal behavior observed along the N-SmA phase transition line yields further strong evidence for the HLM coupling effect. 相似文献
185.
Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria 总被引:1,自引:0,他引:1
Pratibha Pandey S. Merwyn G. S. Agarwal B. K. Tripathi S. C. Pant 《Journal of nanoparticle research》2012,14(1):709-13
Copper (II) oxide multi-armed nanoparticles composed of 500–1000 nm long radiating nanospicules with 100–200 nm width near
the base and 50–100 nm width at the tapered ends and ~25 nm thickness were synthesized by electrochemical deposition in the
presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphology
and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The
CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing
bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano
CuO killed 3 × 108 CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 106 CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano
CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also
been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification
and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings. 相似文献
186.
J. Tripathi J.M. Keller K. Das S. Tripathi T. Shripathi 《Journal of Physics and Chemistry of Solids》2012,73(8):1026-1033
Contribution of Rhodamine B doping on the structural and optical properties of PVA is investigated here. With increasing doping wt%, Raman spectra show the disappearance of main PVA peaks revealing a decrease in crystallinity and breaking of bonds, which also results in modified surface morphology as seen from corresponding SEM measurements. Optical absorption measurements show the possibility of both direct and indirect transitions, also indicating strong modifications in optical properties as a result of doping fluorescent dye in the polymer host. 相似文献
187.
The depletion of non-renewable resources and rise in global warming has caused great concern to humankind. With a view to
use renewable source of energy and to eliminate hazardous chemical compounds from air, soil, and water, photocatalysis utilizing
solar energy is becoming a rapidly expanding technology. Semiconductor nanoparticles have the ability to undergo photoinduced
electron transfer to an adsorbed particle governed by the band energy positions of the semiconductor and the redox potential
of the adsorbate. A brief overview of metal oxides and sulphides that can act as sensitizers for light-induced redox processes
due to their electronic structure is presented here. 相似文献
188.
MK Talari AB Abdul Majeed DK Tripathi M Tripathy 《Chemical & pharmaceutical bulletin》2012,60(7):818-824
The application of nanomaterials has gained considerable momentum in various fields in recent years due to their high reactivity, excellent surface properties and quantum effects in the nanometer range. The properties of zinc oxide (ZnO) vary with its crystallite size or particle size and often nanocrystalline ZnO is seen to exhibit superior physical and chemical properties due to their higher surface area and modified electronic structure. ZnO nanoparticles are reported to exhibit strong bacterial inhibiting activity and silver (Ag) has been extensively used for its antimicrobial properties since ages. In this study, Ag doped ZnO nanoparticles were synthesized by mechanochemical processing in a high energy ball mill and investigated for antimicrobial activity. The nanocrystalline nature of zinc oxide was established by X-ray diffraction (XRD) studies. It is seen from the XRD data obtained from the samples, that crystallite size of the zinc oxide nanoparticles is seen to decrease with increasing Ag addition. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) data also supported the nanoparticle formation during the synthesis. The doped nanoparticles were subjected to antimicrobial investigation and found that both increase in Ag content and decrease in particle size contributed significantly towards antimicrobial efficiency. It was also observed that Ag doped ZnO nanoparticles possess enhanced antimicrobial potential than that of virgin ZnO against the studied microorganisms of Escherichia coli and Staphylococcus aureus. 相似文献
189.
Seerat Fatima Anindra Sharma Rahul Sharma Rama P. Tripathi 《Journal of heterocyclic chemistry》2012,49(3):600-606
One‐pot economical and efficient synthesis of multifunctional 5H‐thiazolo[3,2‐a]pyrimidines by the reaction of 4‐aryl dihydrothiopyrimidines with propargyl bromide in the presence of inorganic base has been reported in very short time. 相似文献
190.
S. J. Sartandel S. V. Bara S. Chinnaesakki R. M. Tripathi V. D. Puranik 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(3):447-451
This paper discusses the measurement of naturally occurring radioactivity materials (NORM) in beach sand minerals using high resolution gamma spectrometry. In India, the beach sand minerals of economic interest from coastal Kerala, Tamil Nadu and Orissa are enriched with NORM due to the occurrence of monazite deposits and heavy minerals such as zircon, ilmenite, magnetite, garnet, rutile etc. Since many of these ores are rich in 232Th and other radio elements, certification of radioactivity levels has become mandatory in recent years. The average activity concentrations of 226Ra in zircon, rutile and garnet were 3,531, 1,134 and 17 Bq kg?1, respectively. The average activity concentration of 232Th observed in zircon, rutile and garnet were 618, 454 and 64 Bq kg?1, respectively. Concentration of 226Ra, 232Th, and 40K in ilmenite ore ranged from 17.6–444 Bq kg?1, 80.4–1971 Bq kg?1 and ≤5.5–25.0 Bq kg?1, respectively. 相似文献