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排序方式: 共有293条查询结果,搜索用时 78 毫秒
131.
Leonida MD Starczynowski DT Waldman R Aurian-Blajeni B 《Analytical and bioanalytical chemistry》2003,376(6):832-837
We present the fabrication and properties of lactate biosensors. The novel feature is the use of polymerized flavin adenine dinucleotide (FAD) as mediator for electron transfer. The biosensors were prepared using lactate dehydrogenase (LDH), lactate oxidase (LOX), or baker's yeast (BY) immobilized at the surface of the electrode. The sensors using purified enzymes showed good sensitivity, linearity, and stability. The sensitivity of the BY electrodes was slightly lower. The advantages of this type of sensors are discussed in connection with potential applications. 相似文献
132.
S. Migge G. Sandmann D. Rahner H. Dietz W. Plieth 《Journal of Solid State Electrochemistry》2005,9(3):132-137
The electrochemical intercalation of lithium into single graphite particles was studied in situ using Raman microscopy combined with confocal microscopy. The degree of intercalation during cycling was obtained from changes in the Raman bands of carbon. Confocal microscopy was used to image the graphite electrode in order to monitor the intercalation into single graphite particles. An industrial button cell was modified such that Raman spectra and microscopic images of the back side of the negative electrode could be taken through a window in the cup of the cell. The liquid electrolyte consisted of a 1:1 mixture of ethylenecarbonate/dimethylcarbonate (EC/DMC) with 1 M LiPF6. The spectroscopy and microscopy showed that lithium does not intercalate into the graphite in a homogeneous manner. Inhomogeneous lithium intercalation was even observed in single graphite particles. 相似文献
133.
Brandon L. Salazar Zoe Y. Marr Jason B. Benedict Luis A. Colón 《Journal of separation science》2023,46(10):2200830
Diarylethene-based photoswitches have become very popular over the last few decades for potential applications in chemistry, materials science, and biotechnology due to their unique physical and chemical properties. We report the isomeric separation of a diarylethene-based photoswitchable compound using high-performance liquid chromatography. The separated isomers were characterized by ultraviolet-visible spectroscopy and mass spectrometry confirmed the isomeric nature of the compounds. The isomers were purified by preparative high-performance liquid chromatography, providing fractionated samples to study the isomers individually. A total amount of 13 mg of an isomer of interest was fractionated from a solution of 0.4 mg/ml of the isomeric mixture. Because the preparative high-performance liquid chromatographic method required large quantities of solvent, we explored the use of supercritical fluid chromatography as an alternative separation mode which, to the best of our knowledge, is the first time this technique is used to separate diarylethene-based photoswitchable compounds. Supercritical fluid chromatography provided faster analysis times while maintaining sufficient baseline resolution for the separated compounds and consuming less organic solvent in the mobile phase compared to high-performance liquid chromatography. It is proposed that the supercritical fluid chromatographic method be upscaled and used in future fractionation of the diarylethene isomeric compounds, becoming a more environmentally benign approach for compound purification. 相似文献
134.
Bachir AI Kolin DL Heinze KG Hebert B Wiseman PW 《The Journal of chemical physics》2008,128(22):225105
Fluctuation-based fluorescence correlation techniques are widely used to study dynamics of fluorophore labeled biomolecules in cells. Semiconductor quantum dots (QDs) have been developed as bright and photostable fluorescent probes for various biological applications. However, the fluorescence intermittency of QDs, commonly referred to as "blinking", is believed to complicate quantitative correlation spectroscopy measurements of transport properties, as it is an additional source of fluctuations that contribute on a wide range of time scales. The QD blinking fluctuations obey power-law distributions so there is no single characteristic fluctuation time for this phenomenon. Consequently, it is highly challenging to separate fluorescence blinking fluctuations from those due to transport dynamics. Here, we quantify the bias introduced by QD blinking in transport measurements made using fluctuation methods. Using computer simulated image time series of diffusing point emitters with set "on" and "off" time emission characteristics, we show that blinking results in a systematic overestimation of the diffusion coefficients measured with correlation analysis when a simple diffusion model is used to fit the time correlation decays. The relative error depends on the inherent blinking power-law statistics, the sampling rate relative to the characteristic diffusion time and blinking times, and the total number of images in the time series. This systematic error can be significant; moreover, it can often go unnoticed in common transport model fits of experimental data. We propose an alternative fitting model that incorporates blinking and improves the accuracy of the recovered diffusion coefficients. We also show how to completely eliminate the bias by applying k-space image correlation spectroscopy, which completely separates the diffusion and blinking dynamics, and allows the simultaneous recovery of accurate diffusion coefficients and QD blinking probability distribution function exponents. 相似文献
135.
J. Philibert Th. P. Nash Jr. St. R. Benedict Clarence E. May H. P. Ross H. Strauss A. Hahn Elisabeth Kootz R. Movy K. L. Gad-Andresen W. Mestrezat M. P. Janet M. Ljungdahl S. Levy-Simpson D. Ch. Carroll J. K. Parnas J. Heller A. Novanowitch A. P. Orr 《Analytical and bioanalytical chemistry》1926,69(9):364-368
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Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)
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Thomas M. Rookes Dr. Elizabeth P. Wildman Dr. Gábor Balázs Dr. Benedict M. Gardner Dr. Ashley J. Wooles Dr. Matthew Gregson Dr. Floriana Tuna Prof. Dr. Manfred Scheer Prof. Dr. Stephen T. Liddle 《Angewandte Chemie (International ed. in English)》2018,57(5):1332-1336
The synthesis and characterisation is presented of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS=N(CH2CH2NSiMe2But)3, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; TrenTIPS=N(CH2CH2NSiPri3)3, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route. 相似文献
139.
Benedict T. W. Lo Lin Ye Jin Qu Junliang Sun Junlin Zheng Dejing Kong Claire A. Murray Chiu C. Tang Shik Chi Edman Tsang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(20):6085-6088
Microporous H‐ZSM‐5 containing one Brønsted acid site per asymmetric unit is deliberately chosen to host pyridine, methanol, and ammonia as guest molecules. By using new‐generation in situ synchrotron X‐ray powder diffraction combined with Rietveld refinement, the slight but significant alteration in scattering parameters of framework atoms modified by the guest molecules enables the user to elucidate their adsorption geometries and interactions with the Brønsted acid sites in H‐ZSM‐5 in terms of atomic distances and angles within experimental errors. The conclusion, although demonstrated in the H‐ZSM‐5, is expected to be transferable to other zeolites. This approach provides a stepping stone towards the rational engineering of molecular interaction(s) with acid sites in zeolitic catalysis. 相似文献
140.
Marjolein J.W. Harmsen - van Hout P. Jean-Jacques Herings Benedict G.C. Dellaert 《European Journal of Operational Research》2013
We model strategic communication network formation with (i) link specificity: link maintenance lowers specific attention and thus value (negative externality previously ignored for communication) and (ii) value transferability via indirect links for informational but not for social value (positive externality modeled uniformly before). Assuming only social value, the pairwise stable set includes many nonstandard networks under high and particular combinations of complete components under low link specificity. Allowing for social and informational value reduces this set to certain fragmented networks under high and the complete network under low link specificity. These extremes are efficient, whereas intermediate link specificity generates inefficiency. 相似文献