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531.
Enzymes are versatile biocatalysts with major advantages of ultrahigh reaction selectivity and specificity under mild conditions, which currently find increasing applications. However, their applications are often hampered by difficulties in recovery and recycling. As a result, we carried out detailed investigations on the synthesis and characterization of silica-encapsulated iron oxide magnetic nanoparticles of controlled dimension as an enzyme carrier. It is shown that the relatively smaller sized silica-coated magnetic nanoparticle prepared by the microemlusion technique can a carry bulky enzyme, beta-lactamase, via chemical linkages on the silica overlayer without severely blocking the enzymatic active center (which is commonly encountered in conventional solid supports). An activity study by Michalis-Menten kinetics reflects that this new type of immobilization allows enzyme isolation with accessibility as good as free enzyme. The recovery and reusability of the nanoparticle-supported enzyme upon application of magnetic separation are also demonstrated. 相似文献
532.
Medley P Yu Z Connors B Klemperer W Tsang SN Chuang CC 《The Journal of chemical physics》2006,124(21):214314
We report the analyses of the three intermolecular combination bands of the hydrogen-bonded N2-HF complex at vHF=3, observed by molecular beam intracavity laser induced fluorescence. The origin of the HF intermolecular bending combination band, (3001(1)0)<--(00000), is 11 548.45(3) cm(-1), 328.2 cm(-1) higher than that of the (30000)<--(00000) transition with an origin at 11 220.250(1) cm(-1). The average rotational constant of the (3001(1)0) level is 0.103 63(1) cm(-1), a 4.8% reduction from B(30000)=0.109 21(1) cm(-1). Perturbations are observed as line splittings, increased line widths, and reduced peak intensities of a number of lines of the e and f components of (3001(1)0). In addition, the centrifugal distortion coefficients of both components are large, negative, and different. The N2 intermolecular bend transition (30001(1))<--(00000) has an origin at 11 288.706(1) cm(-1), 68.456(2) cm(-1) above that of the (30000)<--(00000) transition. This is the lowest combination state at v(HF)=3 level. It is unperturbed, yielding B(30001(1))=0.110.10(1) cm(-1). The transition to the intermolecular stretching state, (30100)<--(00000), has an origin at 11 318.858(1) cm(-1) with B(30100)=0.105 84(1) cm(-1). Both the (30100) and (30000) levels show an isolated perturbation at J=4. The Lorentzian component of the line widths, which show considerable variation with soft mode, are GammaL(30000)=490(30) MHz, GammaL(30100)=630(30) MHz, GammaL(3001(1)0)=250(30) MHz, and GammaL(30001(1))=500(50) MHz. 相似文献
533.
Karaked Tedsree Adam T. S. Kong Dr. Shik Chi Tsang Prof. 《Angewandte Chemie (International ed. in English)》2009,48(8):1443-1446
Formic acid adsorption on ruthenium nanoparticles of different sizes allows differentiation of differently bound formate species by solution 13C NMR spectroscopy (see picture). The chemical shifts are comparable to those of organometallic analogues, thus indicating that formate can act as a probe to distinguish surface features of metallic nanoparticles in solution with good quantification and resolution.
534.
535.
Haitao YuJiang Wang Bin DengXile Wei Yanqiu CheY.K. Wong W.L. ChanK.M. Tsang 《Communications in Nonlinear Science & Numerical Simulation》2012,17(3):1344-1354
In this paper, a robust control system combining backstepping and sliding mode control techniques is used to realize the synchronization of two gap junction coupled chaotic FitzHugh-Nagumo (FHN) neurons in the external electrical stimulation. A backstepping sliding mode approach is applied firstly to compensate the uncertainty which occur in the control system. However, the bound of uncertainty is necessary in the design of the backstepping sliding mode controller. To relax the requirement for the bound of uncertainty, an adaptive backstepping sliding mode controller with a simple adaptive law to adapt the uncertainty in real time is designed. The adaptive backstepping sliding mode control system is robust for time-varying external disturbances. The simulation results demonstrate the effectiveness of the control scheme. 相似文献
536.
The single-walled carbon nanotubes (SWCNT) absorber was fabricated by vertical evaporation method. Mode-locked picosecond Nd-doped solid-state lasers operating at 1.00 and 1.34 ??m and Tm-doped solid-state laser at 2 ??m with SWCNT absorbers were demonstrated, respectively. Watt-level average output powers of continuous wave mode locking were obtained. The operational bandwidth of 1 ??m is broader than other saturable absorbers fabricated by using other types of materials. 相似文献
537.
Po keung Tsang Zhanqiang Fang Hui Liu Xiaolei Chen 《Frontiers of Chemistry in China》2008,3(3):288-293
The kinetics of the adsorption of an endocrine disruptor, di-n-butyl phthalate (DBP), by four different granulated-activated carbons (GACs) is presented in this paper. Results showed that
adsorption of DBP by the four GACs followed first-order kinetics and the adsorption constant of the four GAC was found to
follow the order: nut shell>coconut shell>Coaly carbon 1.0>Coaly carbon 1.5. Batch adsorption studies were also conducted
to investigate the effect of pH on the adsorption process. The optimum pH for the removal of DBP from aqueous solutions under
the experimental conditions used in this work was found to be 5.0. The characterization of the carbon surfaces was conducted
by using scanning electron microscopy (SEM). Furthermore, results from infrared spectroscopic (IR) studies showed that physical
adsorption plays an important role in the adsorption of DBP by the four selected GACs. 相似文献
538.
Saturated Red‐Light‐Emitting Gold(III) Triphenylamine Dendrimers for Solution‐Processable Organic Light‐Emitting Devices 下载免费PDF全文
Man‐Chung Tang Dr. Carmen Ka‐Man Chan Dr. Daniel Ping‐Kuen Tsang Yi‐Chun Wong Dr. Maggie Mei‐Yee Chan Dr. Keith Man‐Chung Wong Prof. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15233-15241
A novel isoquinoline‐containing C^N^C ligand and its phosphorescent triphenylamine‐based alkynylgold(III) dendrimers have been synthesized. These alkynylgold(III) dendrimers serve as phosphorescent dopants in the fabrication of efficient solution‐processable organic light‐emitting devices (OLEDs). The photophysical, electrochemical, and electroluminescence properties were studied. A saturated red emission with CIE coordinates of (0.64, 0.36) and a high EQE value of 3.62 % were achieved. Unlike other red‐light‐emitting iridium(III) dendrimers, a low turn‐on voltage of less than 3 V and a reduced efficiency roll‐off at high current densities were observed; this can be accounted for by the enhanced carrier transporting ability and the relatively short lifetimes in the high‐generation dendrimers. This class of alkynylgold(III) dendrimers are promising candidates as phosphorescent dopants in the fabrication of solution‐processable OLEDs. 相似文献
539.
Ferreira P Phillips E Rippon D Tsang SC Hayes W 《The Journal of organic chemistry》2004,69(20):6851-6859
Nitroxyl radicals such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) are highly selective oxidation catalysts for the conversion of primary alcohols into the corresponding aldehydes. In this study, direct tethering of TEMPO units onto linear poly(ethylene glycol) (PEG) has afforded macromolecular catalysts that exhibit solubility in both aqueous and organic solvents. Recovery of the dissolved polymer-supported catalyst has been carried out by precipitation with a suitable solvent such as diethyl ether. The high catalyst activities and selectivities associated traditionally with nitroxyl-mediated oxidations of alcohols are retained by the series of "linker-less" linear PEG-TEMPO catalysts in which the TEMPO moiety is coupled directly to the PEG support. Although the selectivity remains unaltered, upon recycling of the linker-less polymer-supported catalysts, extended reaction times are required to maintain high yields of the desired carbonyl compounds. Alternatively, attachment of two nitroxyl radicals onto each functionalized PEG chain terminus via a 5-hydroxyisophthalic acid linker affords branched polymer-supported catalysts. In stark contrast to the linker-less catalysts, these branched nitroxyls exhibit catalytic activities up to five times greater than 4-methoxy-TEMPO alone under similar conditions. In addition, minimal decrease in catalytic activity is observed upon recycling of these branched macromolecular catalysts via solvent-induced precipitation. The high catalytic activities and preservation of activity upon recycling of these branched systems is attributed to enhanced regeneration of the nitroxyl species as a result of intramolecular syn-proportionation. 相似文献
540.
M. Schmidt K. Dransfeld E. Cohen A. Ron T. R. Royt R. T. Williams J. P. Long J. C. Rife M. N. Kabler M. M. Salour A. Cingolani M. Ferrara M. Lugarà W. T. Tsang Wei-Lon Cao Fer-Ming Tong De-Sen Shao V. K. Mathur Chi H. Lee D Welford A. Mooradian A. Dandridge H. F. Taylor T. L. Koch L. C. Chiu Ch. Harder A. Yariy 《Applied physics. B, Lasers and optics》1982,28(2-3):208-218