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排序方式: 共有385条查询结果,搜索用时 15 毫秒
61.
Forrest Nichols Dr. Jia En Lu Rene Mercado Ryan Dudschus Prof. Frank Bridges Prof. Shaowei Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(18):4136-4142
Electrochemical hydrogen generation is a rising prospect for future renewable energy storage and conversion. Platinum remains a leading choice of catalyst, but because of its high cost and low natural abundance, it is critical to optimize its use. In the present study, platinum oxide nanoparticles of approximately 2 nm in diameter are deposited on carbon nitride (C3N4) nanosheets by thermal refluxing of C3N4 and PtCl2 or PtCl4 in water. These nanoparticles exhibit apparent electrocatalytic activity toward the hydrogen evolution reaction (HER) in acid. Interestingly, the HER activity increases with increasing Pt4+ concentration in the nanoparticles, and the optimized catalyst even outperforms commercial Pt/C, exhibiting an overpotential of only −7.7 mV to reach the current density of 10 mA cm−2 and a Tafel slope of −26.3 mV dec−1. The results from this study suggest that the future design of platinum oxide catalysts should strive to maximize the Pt4+ sites and minimize the formation of the less active Pt2+ species. 相似文献
62.
Nabil N. AL‐Hashimi Rand O. Shahin Aqeel N. AL‐Hashimi Ajeal M. Al Ajeal Lubna H. Tahtamouni Chanbasha Basheer 《Biomedical chromatography : BMC》2019,33(2)
A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs. 相似文献
63.
Michael A. Nichols Rachel M. Sobinsky Allen D. Hunter Matthias Zeller 《Journal of chemical crystallography》2007,37(6):433-438
The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator
for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane
as a centrosymmetric dimer in the monoclinic space group P21/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally
twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6
has a planar central Li2C2 core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified
three structural motifs that affect Li2C2 dimer ring planarity. 相似文献
64.
Nanochannels in SU-8 with floor and ceiling metal electrodes and integrated microchannels 总被引:2,自引:0,他引:2
Sacrificially etched 2-D nanofluidic channels and nanospaces with integrated floor and ceiling electrodes and arbitrary channel geometries have been demonstrated with channel heights from 20 nm to 400 nm, widths from 800 nm to 40 microm, and lengths up to 3 mm, using SU-8 as the channel structural material. 相似文献
65.
Wemhoff AP Howard WM Burnham AK Nichols AL 《The journal of physical chemistry. A》2008,112(38):9005-9011
A new chemical kinetic model for the beta-delta transition and decomposition of LX-10 (95% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, 5% Viton A binder) is presented here. This model implements aspects of previous kinetic models but calibrates the model parameters to data sets of three experiments: differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and one-dimensional time to explosion (ODTX). The calibration procedure contains three stages: one stage uses open-pan DSC and TGA to develop a base reaction for formation of heavy gases, a second stage features closed-pan DSC to ascertain the autocatalytic behavior of reactant gases attacking the solid explosive, and a final stage adjusts the rate for the breakdown of heavy reactant gases using ODTX experimental data. The resultant model presents a large improvement in the agreement between simulated DSC and TGA results and their respective experiments while maintaining the same level of agreement with ODTX, scaled thermal explosion, and laser heating explosion times when compared to previous models. 相似文献
66.
Microwave activation of enzymatic catalysis 总被引:2,自引:0,他引:2
Young DD Nichols J Kelly RM Deiters A 《Journal of the American Chemical Society》2008,130(31):10048-10049
Microwave irradiation can be used to regulate biocatalysis. Herein, the utilization of hyperthermophilic enzymes in a microwave reactor is reported. While these enzymes are inactive at low temperatures, they can be activated with microwave irradiation. To the best of our knowledge, this is the first illustration of a specific microwave effect in enzymatic catalysis. 相似文献
67.
The authors time resolve molecular motion in bound state, ionic potentials that leads to bond cleavage during the interaction with intense, ultrafast laser fields. Resonances in molecular ions play an important role in dissociative ionization with ultrafast laser fields, and the authors demonstrate how these resonances evolve in time to produce dissociation after initial strong-field ionization. Exploiting such dynamic resonances offers the possibility of controlled bond breaking and characterizing time-dependent molecular structure. 相似文献
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