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排序方式: 共有261条查询结果,搜索用时 18 毫秒
111.
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113.
G. Mazumdar M. De A. Mukhopadhyay S. K. Mazumdar N. Mazumder A. K. Das Edward E. Knaus 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):494-495
In the title compound, C14H19IN2O8, an almost planar heterocyclic base is oriented anti with respect to the puckered sugar moiety. The sugar pucker is C2′‐endo/C3′‐exo, the N‐glycosidic torsion angle is 166.4 (4)° and the conformation of O5′ is +sc. The molecules are linked by hydrogen bonds of the types N—H?O and O—H?O. 相似文献
114.
Dr. Sandeep K. Sharma Jitendra Bahadur Dr. Pushkar N. Patil Priya Maheshwari Dr. Saurabh Mukherjee Dr. Kathi Sudarshan Dr. Subhasish Mazumder Dr. Pradeep K. Pujari 《Chemphyschem》2013,14(5):1055-1062
Chitosan–NiO nanocomposite (CNC) is shown to be a potential dielectric material with promising properties. CNCs containing NiO nanoparticles (0.2, 0.6, 1, 2, 5 wt %) are prepared through chemical methods. The inclusion of NiO nanoparticles in the chitosan matrix is confirmed by scanning electron microscopy (SEM) and X‐ray diffraction. The morphology of the NiO nanoparticles and the nanocomposites is investigated by transmission electron microscopy and SEM, respectively. Positron annihilation lifetime spectroscopy (PALS) and the coincidence Doppler broadening (CDB) technique are used to quantify the free volume and molecular packing in the nanocomposites. The triplet‐state positronium lifetime and the corresponding intensity show the changes in nanohole size, density, and size distribution as a function of NiO loading. Small‐angle X‐ray scattering indicates that the NiO aggregates are identical in all the CNCs. The momentum density distribution obtained from CDB measurements excludes the possibility of a contribution of vacant spaces (pores) available in NiO aggregates to the free volume of nanocomposites upon determination by using PALS. The results show systematic variation in free‐volume properties and nano‐level molecular packing as a function of NiO loading, which is presumed to play a vital role in determining the various properties of the nanocomposites. 相似文献
115.
Metallogels Derived from Silver Coordination Polymers of C3‐Symmetric Tris(pyridylamide) Tripodal Ligands: Synthesis of Ag Nanoparticles and Catalysis 下载免费PDF全文
Mithun Paul Koushik Sarkar Prof. Parthasarathi Dastidar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):255-268
By applying a recently developed crystal engineering rationale, four C3 symmetric tris(pyridylamide) ligands namely 1,3,5‐tris(nicotinamidomethyl)‐2,4,6‐triethylbenzene, 1,3,5‐tris(isonicotinamidomethyl)‐2,4,6‐triethylbenzene, 1,3,5‐tris(nicotinamidomethyl)‐2,4,6‐trimethylbenzene, and 1,3,5‐tris(isonicotinamidomethyl)‐2,4,6‐trimethylbenzene, which contain potential hydrogen‐bonding sites, were designed and synthesized for generating AgI coordination polymers and coordination‐polymer‐based gels. The coordination polymers thus obtained were characterized by single‐crystal X‐ray diffraction. The silver metallogels were characterized by transmission electron microscopy (TEM) and dynamic rheology. Upon exposure to visible light, these silver metallogels produced silver nanoparticles (AgNPs), which were characterized by TEM, powder X‐ray diffraction, energy dispersive X‐ray and X‐ray photoelectron spectroscopy. These NPs were found to be effectively catalyzed the reduction of 4‐nitrophenolate to 4‐aminophenolate without the use of any exogenous reducing agent. 相似文献
116.
Pardasani D Mazumder A Gupta AK Kanaujia PK Tak V Dubey DK 《Rapid communications in mass spectrometry : RCM》2007,21(18):3109-3114
Retrospective detection and identification of markers of chemical warfare agents are important aspects of verification of the Chemical Weapons Convention. Alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs) are important markers of nerve agents. We describe the development and optimization of a new gas chromatography/mass spectrometry (GC/MS) injection port fluorination method for the derivatization of AAPAs and APAs. The process involved the injection of acids with trifluoroacetic anhydride in GC/MS, where acids are converted into their corresponding volatile fluorides. Various reaction conditions such as fluorinating agent, injection port temperature and splitless time were optimized. The maximum reaction efficiency of the acids with trifluoroacetic anhydride was observed at 230 degrees C injection port temperature with a splitless time of 2 min. APAs showed best analytical efficiencies at 400 degrees C injection port temperature, while the other conditions were similar to those of AAPAs. The linearities of response for APAs and AAPAs were in the range of 1-25 and 5-100 microg mL(-1), respectively, with limits of detection ranging from 500 pg to 800 ng mL(-1). 相似文献
117.
Mazumder S Sen D Patra AK Khadilkar SA Cursetji RM Loidl R Baron M Rauch H 《Physical review letters》2004,93(25):255704
Predictions of nonlinear theories on dynamics of new phase formation have been examined for the hydration of calcium silicates with light water and heavy water. In the case of hydration with light water, reasonable agreement has been observed with dynamical scaling hypothesis with a new measure of the characteristic length. The characteristic length does not follow a power law relation with time. Hydrating mass is found to be mass fractal throughout hydration, with mass fractal dimension increasing with time. But, in the case of hydration with heavy water, no agreement has been observed with the scaling hypothesis. Hydrating mass undergoes transition from mass fractal to surface fractal and finally again to mass fractal. The qualitative features of the kinetics of hydration, as measured in small-angle scattering experiments, are strikingly different for hydration with light water and heavy water. 相似文献
118.
First-principles calculations are performed to study energetics and kinetics of hydrogen in ZnO, in particular, the H(-) anion and the H(2) molecule on the interstitial site and in the oxygen vacancy. We show that the H(2) molecule kinetically trapped in the oxygen vacancy, rather than interstitial H(2), can explain a variety of experimental observations on "hidden" hydrogen in ZnO. The accumulation of shallow donors, especially the substitutional H, near the ZnO surface is important to the formation of hidden hydrogen in the ZnO bulk and can also lead to persistent photoconductivity. 相似文献
119.
J. Bahadur D. Sen S. Mazumder V. K. Aswal V. Bedekar R. Shukla A. K. Tyagi 《Pramana》2008,71(5):959-963
Effects of sintering on pore morphology and dielectric response have been investigated. Pore structure has been probed by
small angle neutron scattering (SANS). It has been observed that the size distribution becomes less polydisperse with a slight
modification in the distribution as sintering temperature is increased. Dielectric response in the frequency range 0.02–1000
kHz is significantly altered by modification of pore structure because of sintering. A transition from non-Debye type to near-Debye
type response has been observed as the sintering temperature is increased.
相似文献
120.
Nanocrystalline nickel oxide powders were calcined at 300, 600 and 900°C and pore structure evolution was followed by small
angle neutron scattering (SANS). Pore size distributions at two widely separated size ranges have been revealed. Shrinkage
of larger-sized pore with reduction in polydispersity has been observed with increasing heat treatment temperature. The pore
structures at various heat treatment temperatures do not scale. This has been attributed to the grain boundary diffusion leading
to an asymmetric shrinkage of the pores.
相似文献