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71.
Hai Yan Nan Zhen Hua Ni Jun Wang Zainab Zafar Zhi Xiang Shi Ying Ying Wang 《Journal of Raman spectroscopy : JRS》2013,44(7):1018-1021
The thermal stability in air of graphene synthesized by either chemical vapor deposition or mechanical cleavage is studied. It is found that single layer graphene prepared by both methods starts to show defects at ~500 °C, indicated by the appearance of a disorder‐induced Raman D peak. The defects are initially sp3 type and become vacancy like at higher temperature. On the other hand, bilayer graphene shows better thermal stability, and the D peak appears at ~600 °C. These results are quite different from those annealing in vacuum and controlled atmosphere. Raman images show that the defects in chemical vapor deposition graphene are not homogeneous, whereas those in mechanical cleavage graphene are uniformly distributed across the whole sample. The factors that affect the thermal stability of graphene are discussed. Our results could be important for guiding the future electronics process and chemical decoration of graphene. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
72.
Saidbakhrom Saidjalolov Dr. Emmanuelle Braud Dr. Zainab Edoo Dr. Laura Iannazzo Dr. Filippo Rusconi Dr. Margaux Riomet Dr. Antoine Sallustrau Dr. Frédéric Taran Dr. Michel Arthur Dr. Matthieu Fonvielle Prof. Dr. Mélanie Etheve-Quelquejeu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(28):7687-7695
β-Lactams, the cornerstone of antibiotherapy, inhibit multiple and partially redundant targets referred to as transpeptidases or penicillin-binding proteins. These enzymes catalyze the essential cross-linking step of the polymerization of cell wall peptidoglycan. The understanding of the mechanisms of action of β-lactams and of resistance to these drugs requires the development of reliable methods to characterize their targets. Here, we describe an activity-based purification method of β-lactam targets based on click and release chemistry. We synthesized alkyne-carbapenems with suitable properties with respect to the kinetics of acylation of a model target, the Ldtfm L,D-transpeptidase, the stability of the resulting acylenzyme, and the reactivity of the alkyne for the cycloaddition of an azido probe containing a biotin moiety for affinity purification and a bioorthogonal cleavable linker. The probe provided access to the fluorescent target in a single click and release step. 相似文献
73.
A series of Cu (II) complexes bearing asymmetric derivatives of (R,R)‐1,2‐diaminocyclohexane were synthesised and characterised. The X‐ray structures of the complexes showed distorted square planar geometry. The catalytic activities of in situ‐generated copper acetate complexes in the presence of 10 mol% of N,N‐diisopropylethylamine were evaluated in the asymmetric Henry reaction. The current catalysts showed high enantioselectivity (up to 99%) for (S)‐1‐nitro‐4‐phenylbutan‐2‐ol from the reaction of 3‐phenylpropanal and nitromethane. 相似文献
74.
Lawal Monsurat M. Sanusi Zainab K. Govender Thavendran Tolufashe Gideon F. Maguire Glenn E. M. Honarparvar Bahareh Kruger Hendrik G. 《Structural chemistry》2019,30(1):409-417
Structural Chemistry - We give an account of a one-step concerted catalytic mechanism of HIV-1 protease (PR) hydrolysis of its natural substrate using a hybrid QM/MM method. The mechanism is a... 相似文献
75.
Basit Muhammad Abdul Tariq Zeeshan Zahid Saira Khan Sheheryar Siddiqui Farrukh Arsalan Khan Muhammad Farooq Ali Gohar Park Tae Joo 《Journal of Cluster Science》2022,33(6):2443-2454
Journal of Cluster Science - Successive ionic layer adsorption and reaction (SILAR) process has been diversely used for deposition of various metal chalcogenides. SnS is one of them. Owing to the... 相似文献
76.
Wedad A. Al-Onazi Amal M. Al-Mohaimeed Zainab M. Almarhoon Eida S. Al-Farraj Asma A. Alothman 《中国化学会会志》2020,67(1):125-134
A potentiometric method was used to determine the stability constants for the various complexes of copper(II) with carbamoylcholine chloride (C) drug as a ligand in the presence of some biorelevant amino acid constituents like glycine (Gly), alanine (Ala), valine (Val), proline (Pro), β-phenylalanine (Phe), S-methylcysteine (Met), threonine (Thr), ornithine (Orn), lysine (Lys), histidine (Hisd), histamine (Hist), and imidazole (Imz) as ligands (L). Stability constants of complexes were determined at 25°C and I = 0.10 mol/L NaNO3. The relative stability of each ternary complex was compared with that of the corresponding binary complexes in terms of Δlog K and % R.S. values. Cu(II) complexes of drug C were synthesized in 1:1 and 1:1:1 M ratios of copper to drug [Cu(C)(NO3)2] (1) and copper to drug to glycine[Cu(C)(Gly)(NO3)].NO3 (2), respectively. Glycine ternary complex with drug and copper [Cu(C)(Gly)(NO3)].NO3 was considered as representative amino acid. The complexes 1 and 2 were isolated and characterized using various physicochemical and spectral techniques. Both complexes 1 and 2 were found to have magnetic moments corresponding to one unpaired electron. The possible square planar and square-pyramidal geometries of the copper (II) complexes were assigned on the basis of electron paramagnetic resonance (EPR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), ultraviolet–visible (UV–Vis) and infrared (IR) spectral studies, and the discrete Fourier transform method from DMOL3 calculations. Antioxidant activities of all the synthesized compounds were also investigated. 相似文献
77.
Dr. Yang Yang Dr. Saira Ajmal Yiqing Feng Dr. Kejian Li Dr. Xiuzhen Zheng Prof. Liwu Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(18):4080-4089
It is still poorly understood how the first intermediates of CO2 reduction are formed and converted to multi-carbon products over Cu-based electrodes. Herein, Ag is used to decorate dendritic Cu and a high Faradaic efficiency (FE) for C2H4 (25 %) is obtained on a CuAg electrode, which is about five times higher than dendritic Cu. The intermediates including *CO2−, OH groups, Cu-CO, C-O rotation, and CHx species are investigated by in situ Raman spectroscopy. This work provides spectroscopic evidence that the first intermediate of CO2 reduction on Ag-decorated Cu is carboxylate anion *CO2− bonded with the catalyst surface through the C and O atom. The formation and evolution process of the *CO2− intermediate over the applied potential are investigated in depth as well. This research contributes to a better understanding of the mechanism of CO2 reduction and multi-carbon product formation pathways over Ag-decorated Cu. 相似文献
78.
Siliang Ming Dr. Saira Qurban Prof. Dr. Yu Du Prof. Dr. Weiping Su 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(50):12742-12746
Unlike the comprehensive development of tandem multi-metallic catalysis, bimetallic synergistic catalysis has been challenging to achieve high stereoselectivity with the generation of multi-stereogenic centers. Herein, an efficient synergistic catalysis for the diastereo- and enantioselective synthesis of multi-substituted tetrahydrofuran derivatives has been developed. Under mild reaction conditions, a series of target molecules with three consecutive stereocenters were synthesized by a palladium(0)/rhodium(III) bimetal-catalyzed asymmetric decarboxylative [3+2]-cycloaddition of vinylethylene carbonates with α,β-unsaturated carbonyl compounds. The corresponding adducts were obtained with moderate to high yields (67 %∼98 %) and excellent stereoselectivities (>20 : 1 d.r., up to 99 % ee). 相似文献
79.
Abdulrhman Alsayari Abdullatif Bin Muhsinah Yahya I. Asiri Faiz A. Al-aizari Nabila A. Kheder Zainab M. Almarhoon Hazem A. Ghabbour Yahia N. Mabkhot 《Molecules (Basel, Switzerland)》2021,26(17)
The pharmacological activities of thiazole and pyrazole moieties as antimicrobial and anticancer agents have been thoroughly described in many literature reviews. In this study, a convenient synthesis of novel pyrazolo[5,1-b]thiazole-based heterocycles was carried out. The synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy and mass spectrometry. Some selected examples were screened and evaluated for their antimicrobial and anticancer activities and showed promising results. These products could serve as leading compounds in the future design of new drug molecules. 相似文献
80.
The novel characteristics of magnetic field and entropy generation in mixed convective flow of Carreau fluid towards a stretched surface are investigated.Buongiornio nanoliquid model consists of thermophoresis and Brownian movement aspects is opted for analysis.Energy expression is modeled subject to thermal radiation and viscous dissipation phenomenon.Concentration by zero mass flux condition is implemented.Consideration of chemical reaction and activation energy characterizes the mass transfer mechanism.Total entropy generation rate and Bejan number is formulated.The utilization of transformation variables reduces the PDEs into non-linear ODEs.The obtained nonlinear complex problems are computed numerically through Shooting scheme.The impact of involved variables like local Weissenberg number,magnetic parameter,thermal radiation parameter,Brownian motion parameter,thermophoresis parameter,buoyancy ratio parameter,mixed convection parameter,Prandtl parameter,Eckert number,Schmidt number,non-dimensional activation energy parameter,chemical reaction parameter,Brinkman number,dimensionless concentration ratio variable,diffusive variable and dimensionless temperature ratio variable on velocity,temperature,nanoparticles concentration,entropy generation,Bejan number,surface drag force and heat transfer rate are examined through graphs and tables. 相似文献