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141.
Dohnal P Hejduk M Varju J Rubovič P Roučka Š Kotrík T Plašil R Glosík J Johnsen R 《The Journal of chemical physics》2012,136(24):244304
Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that H(3)(+) recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution. 相似文献
142.
Metallic impurities within carbon nanotubes (CNTs) are considered as the main cause of their toxicity. Ultrasonication is a common procedure used to purify and obtain homogeneous dispersions of CNTs as well as to mix them with other components for further processing into composites. Herein, the influence of ultrasonication upon the bioavailability of metallic impurities in CNTs was investigated. We showed that even ultrasonication times as short as 5?min significantly enhanced the bioavailability of metallic impurities, which can therefore interact more actively with biologically important molecules. These findings will have profound impact on the processing of CNTs as well as on nanotoxicity studies. 相似文献
143.
An overview of the chemistry and microbiology of calcareous sponges (Calcispongiae) is provided, highlighting the potential of these sessile filter-feeding marine invertebrates and their associated bacteria for the discovery of new bioactive natural products. 103 compounds are presented and 116 references cited. 相似文献
144.
The synthesis and electrochemical performance of three‐dimensionally ordered macroporous (3DOM) nitroxide polymer brush electrodes for organic radical batteries are reported. The 3DOM electrodes are synthesized via polystyrene colloidal crystal templating with electropolymerization of polypyrrole, modification of surface initiator, and surface‐initiated atom transfer radical polymerization. The discharge capacity of the 3DOM electrodes is proportional to the thickness of the inverse opal. The discharge capacity of the 3DOM electrode at a discharge rate of 5 C is 40 times higher than that of the planar electrode; its cycle‐life performance exhibits 96.1% retention after 250 cycles. 相似文献
145.
This paper introduces an interesting analyte derivatization approach for improved electrochemical detection of amoxicillin (one of the most frequently used β‐lactam antibiotics). It is based on the well‐known chemical conversion of catechols to o‐quinones by MnO2 that can be subsequently easily determined by electrochemical reduction at inexpensive screen‐printed carbon electrodes. The MnO2 reactor is essential to the proposed amperometric sensor not only to increase the electroactivity but also to achieve the detection selectivity. Under the optimized conditions of applied potential=0.0 V vs. Ag/AgCl and flow rate=500 μL/min, the measurement range was over 3 orders of magnitude with a detection limit (S/N=3) of 17 nM. 相似文献
146.
George J. Jiang Jyh Ming Hwu 《Journal of polymer science. Part A, Polymer chemistry》2000,38(7):1184-1194
Methyl methacrylate was polymerized with Cp2YCl(THF) or IVB group metallocene compounds (i.e., Cp2ZrCl2 and Cp2HfCl2, etc.), in the presence of a Lewis acid like Zn(C2H5)2. The Lewis acid was complexed with methyl methacrylate, which avoided the metallocene compounds being poisoned with a functional group. A living polymerization was promoted through the use of metallocene/MAO/Zn(C2H5)2, which gave tactic poly(methyl methacrylate) with a high molecular weight. The polymer yield increases with polymerization time, which indicates that the propagation rate is zero in order in the concentration of the monomer. The polymer yield increases also with the concentration of Cp2YCl(THF), which indicates the yttrocene to be the real catalyst. When the polymerization temperature exceeds room temperature, the poly(methyl methacrylate) cannot be synthesized by the Cp2YCl(THF) catalyst. When the reaction temperature reachs −60 °C, the poly(methyl methacrylate) is high syndiotatic and molecular weight by the Cp2YCl(THF)/MAO catalyst system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1184–1194, 2000 相似文献