排序方式: 共有87条查询结果,搜索用时 31 毫秒
61.
62.
Deposition and characterization of low temperature silicon nitride films deposited by inductively coupled plasma CVD 总被引:1,自引:0,他引:1
Abhijeet Kshirsagar Pradeep NyaupaneDhananjay Bodas S.P. DuttaguptaS.A. Gangal 《Applied Surface Science》2011,257(11):5052-5058
Silicon nitride films have been deposited at a low temperature (70 °C) by inductively coupled plasma chemical vapor deposition (ICP-CVD) technique and their physical and chemical properties were studied. For a deposited SiN sample, β-phase was observed and refractive index of 2.1 at 13.18 nm/min deposition rate was obtained. The attained stress of 0.08 GPa is lower as compared to the reported value of 1.1 GPa for SiN thin films. To study the deposited film, characterization was performed using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), micro Raman spectroscopy, Fourier transfer infrared spectroscopy (FTIR), cross-section scanning electron microscopy (SEM) and atomic force microscopy (AFM). 相似文献
63.
A robust and water-stable porous coordination polymer [Cd(NDC)(0.5)(PCA)]·G(x) (1) (H(2)NDC = 2,6-napthalenedicarboxylic acid, HPCA = 4-pyridinecarboxylic acid, G = guest molecules) with new network topology has been synthesized solvothermally. The framework is 3D porous material and forms a 1D channel along the c-axis, with the channel dimensions ~9.48 × 7.83 ?(2). The compound has high selectivity in uptake of CO(2) over other gases (H(2), O(2), Ar, N(2), and CH(4)). The framework is highly stable in presence of water vapor even at 60 °C. The high CO(2) selectivity over other gases and water stability makes the compound promising candidate for industrial postcombustion gas separation application. 相似文献
64.
Viraj De Silva Boris B. Averkiev Abhijeet S. Sinha Christer B. Aakery 《Molecules (Basel, Switzerland)》2021,26(14)
In order to explore how specific atom-to-atom replacements change the electrostatic potentials on 1,3,4-chalcogenadiazole derivatives, and to deliberately alter the balance between intermolecular interactions, four target molecules were synthesized and characterized. DFT calculations indicated that the atom-to-atom substitution of Br with I, and S with Se enhanced the σ-hole potentials, thus increasing the structure directing ability of halogen bonds and chalcogen bonds as compared to intermolecular hydrogen bonding. The delicate balance between these intermolecular forces was further underlined by the formation of two polymorphs of 5-(4-iodophenyl)-1,3,4-thiadiazol-2-amine; Form I displayed all three interactions while Form II only showed hydrogen and chalcogen bonding. The results emphasize that the deliberate alterations of the electrostatic potential on polarizable atoms can cause specific and deliberate changes to the main synthons and subsequent assemblies in the structures of this family of compounds. 相似文献
65.
Dhananjay Yadav Gaurav Shukla Monish A. Ansari Abhijeet Srivastava Maya Shankar Singh 《Tetrahedron》2018,74(40):5920-5931
An operationally simple and efficient one-pot method for the synthesis of 1-aroyl (or alkanoyl)-2-thioalkyl-3-aryl (or alkyl)-3H-benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones has been devised by copper-catalyzed cross-coupling of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols in open air for the first time. The key to the success of this transformation is the room temperature oxidation of α-/β-naphthol to 1,2-naphthoquinone as a reactive species, which undergoes formal [3 + 2] annulation with α-oxoketene N,S-acetals/β-ketothioamides via cascade sequence of Michael addition/tautomerization/oxidation/cyclization/aromatization reactions, enabling addition of a pyrrole/thiophene ring onto naphthoquinone moiety. Further, benzo[e]indole-4,5-diones were transformed to pentacyclic fused phenazine derivatives under solvent-free conditions. Based on our experimental outcomes, a tentative mechanistic rationale for this chemoselective protocol is proposed, which is well validated and supported by the control experiments. 相似文献
66.
An efficient, environmentally benign and molecular iodine promoted protocol was described for cascade synthesis of two kinds of novel dihydro-1H-pyrrole derivatives, 5 and 7. Compounds 5 were prepared via four-component reaction between diethyl acetylenedicarboxylate (DEAD), aromatic amines and phenylglyoxal monohydrate catalyzed by 10 mol% of iodine in ethanol at room temperature. In addition, using same reaction conditions, a three-component reaction between (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM), aromatic amines and arylglyoxal monohydrate was performed to access product 7. These transformations apparently proceed through an imine intermediate followed by iodine induced Mannich reaction and subsequent intra-molecular cyclization sequences. The protocol involves the formation of CN, CC and OH bonds leading to the preparation of a hexa substituted five membered ring with two stereo centres. The syntheses avoid the use of traditional column chromatography and recrystallization purification methods and, hence, follow the group-assisted purification (GAP) chemistry process. 相似文献
67.
Lyophilization with salts has been identified as an important method of activating enzymes in organic media. Using salt-activated enzymes to transform molecules tethered to solid surfaces in organic phase requires solubilization of enzymes in the solvents. Methods of improving performance of salt-lyophilized enzymes, further, via chemical modification, and use of surfactants and surfactants to create fine emulsions prior to lyophilization are investigated. The reaction system used is transesterification of N-acetyl phenylalanine ethyl ester with methanol or propanol. Initial rate of formation of amino acid esters by subtilisin Carlsberg (SC) was studied and found to increase two to sevenfold by either chemical modification or addition of surfactants in certain solvents, relative to the salt (only)-lyophilized enzyme. The method to prepare highly dispersed enzymes in a salt-surfactant milieu also improved activity by two to threefold. To test the effect of chemical modification on derivatization of drug molecules, acylation of bergenin was investigated using chemically modified SC. 相似文献
68.
We obtain a relation between the longitudinal structure function F
L(x, Q
2), F
2(x, Q
2) and G(x, Q
2) at small x, using the formalism recently reported by one of the authors [2]. We also obtain a relation between F
L(x, Q
2), F
2(x, Q
2) and its slope (dF
2(x, Q
2))/(dlnQ
2). This provides us with the determination of the longitudinal structure function F
L(x, Q
2) from F
2(x, Q
2) data and hence extract the gluon distribution G(x, Q
2). 相似文献
69.
Anugula Nagaraju B. Janaki Ramulu Gaurav Shukla Abhijeet Srivastava Girijesh Kumar Verma Keshav Raghuvanshi Maya Shankar Singh 《Tetrahedron letters》2014
An operationally simple, economical, and straightforward synthesis of diverse 4,5-disubstituted 1,2,3-thiadiazoles from α-enolicdithioesters has been achieved via nitrosation/reduction/diazotization/cyclization sequence in one-pot through the formation of cascade 1–2 (N–S) and 3–4 (C–N) bonds. Importantly, this is the first straightforward entry to highly functionalized 1,2,3-thiadiazoles from dithioesters. 相似文献
70.
Dr. Mari Annadhasan Abhijeet R. Agrawal Surojit Bhunia Vuppu Vinay Pradeep Prof. Sanjio S. Zade Prof. C. Malla Reddy Prof. Rajadurai Chandrasekar 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(33):13956-13962
We present the one-dimensional optical-waveguiding crystal dithieno[3,2-a:2′,3′-c]phenazine with a high aspect ratio, high mechanical flexibility, and selective self-absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave more like plastic crystals due to significant surface adherence, making them suitable for constructing photonic circuits via micromechanical operation with an atomic-force-microscopy cantilever tip. The flexible crystalline waveguides display optical-path-dependent FL signals at the output termini in both straight and bent configurations, making them appropriate for wavelength-division multiplexing technologies. A reconfigurable 2×2-directional coupler fabricated via micromanipulation by combining two arc-shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals. 相似文献