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排序方式: 共有188条查询结果,搜索用时 15 毫秒
101.
Dr. Chi‐Ming Ho Chi‐Kit Wong Dr. Sammi King‐Woon Yau Dr. Chun‐Nam Lok Prof. Chi‐Ming Che 《化学:亚洲杂志》2011,6(9):2506-2511
We have recently reported a kinetic and mechanistic study on oxidative dissolution of silver nanoparticles (AgNPs) by H2O2. In the present study, the parameters that govern the dissolution of AgNPs by O2 were revealed by using UV/Vis spectrophotometry. Under the same reaction conditions (Tris‐HOAc, pH 8.5, I=0.1 M at 25 °C) the apparent dissolution rate (kapp) of AgNPs (10±2.8 nm) by O2 is about 100‐fold slower than that of H2O2. The reaction rate is first‐order with respect to [Ag0], [O2], and [Tris]T, and inverse first‐order with respect to [Ag+] (where [Ag0]=total concentration of Ag metal and [Tris]T=total concentration of Tris). The rate constant is dependent on the size of AgNPs. No free superoxide (O2−) and hydroxyl radical (⋅OH) were detected by trapping experiments. On the basis of kinetic and trapping experiments, an amine‐activated pathway for the oxidation of AgNPs by O2 is proposed. 相似文献
102.
The synthesis of a penta(1-methylpyrazole)ferrocenyl phosphine oxide ligand (1) [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))] is reported together with its X-ray crystal structure. Its self-assembly behavior with a dirhodium(II) tetraoctanoate linker (2) [Rh(2)(O(2)CC(7)H(15))(4)] was investigated for construction of fullerene-like assemblies of composition [(ligand)(12)(linker)(30)]. Reaction between 1 and 2 in acetonitrile resulted in the formation of a light purple precipitate (3). Evidence for the ligand-to-linker ratio of 1:2.5 expected for a fullerene-like structure [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))](12)[Rh(2)(O(2)CC(7)H(15))(4)](30) was obtained from (1)H NMR and elemental analysis. IR and Raman studies confirmed the diaxially bound coordination environment of the dirhodium linker by comparing the stretching frequencies of the carboxylate group and the rhodium-rhodium bond with those in model compound (5), [Rh(2)(O(2)CC(7)H(15))(4)](C(3)H(3)N(2)CH(3))(2), the bis-adduct of linker 2 with 1-methylpyrazole. X-ray powder diffraction and molecular modeling studies provide additional support for the formation of a spherical molecule topologically identical to fullerene with a diameter of approximately 38 ? and a molecular formula of [(1)(12)(2)(30)]. Dissolution of 3 in tetrahydrofuran (THF) followed by layering with acetonitrile afforded purple crystals of [(1)(2)(2)](∞) (6) [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))][Rh(2)(O(2)CC(7)H(15))(4)](2) with a two-dimensional polymeric structure determined by X-ray crystallography. The dirhodium linkers link ferrocenyl units by coordination to the pyrazoles but only four of the five pyrazole moieties of the pentapyrazole ligand are coordinated. The ligand-to-linker ratio of 1:2 in 6 was confirmed by (1)H NMR spectroscopy and elemental analysis, while results from IR and Raman are in agreement with the diaxially coordinated environment of the linker observed in the solid state. 相似文献
103.
Chi Lok Wong U. S. Dinish Kavitha Devi Buddharaju Michael Stenbæk Schmidt Malini Olivo 《Applied Physics A: Materials Science & Processing》2014,117(2):687-692
In this paper, we present surface-enhanced Raman scattering (SERS)-based volatile organic compounds (VOCs) detection with bimetallic nanogap structure substrate. Deep UV photolithography at the wavelength of 250 nm is used to pattern circular shape nanostructures. The nanogap between adjacent circular patterns is 30 ± 5 nm. Silver (30 nm) and gold (15 nm) plasmonic active layers are deposited on the nanostructures subsequently. SERS measurements on different concentrations of acetone vapor ranged from 0.7, 1.5, 3.5, 10.3, 24.5 % and control have been performed with the substrate. The measurement results are found reproducible, and the detection limit is found to be 9.5 pg (acetone molecule). The detection sensitivity is 28.7 % higher than that of the recent reported leaning silicon nanopillar substrate. With further system miniaturization, the sensing technique can work as a portable SERS-based VOCs detection platform for point-of-care breath analysis, homeland security, chemical sensing and environmental monitoring. 相似文献
104.
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106.
Olivier Oms Dr. Thibaut Jarrosson Dr. Lok H. Tong Dr. Andrea Vaccaro Dr. Gérald Bernardinelli Dr. Alan F. Williams Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5012-5022
The fiveway junction : The synthesis of ligands with five symmetrically diverging binding sites is described and their assembly into large spherical structures (such as that shown here) investigated.
107.
108.
Di Hu Chen Yang Chun‐Nam Lok Fangrong Xing Pui‐Yan Lee Yi Man Eva Fung Haibo Jiang Chi‐Ming Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11030-11034
New anticancer platinum(II) compounds with distinctive modes of action are appealing alternatives to combat the drug resistance and improve the efficacy of clinically used platinum chemotherapy. Herein, we describe a rare example of an antitumor PtII complex targeting a tumor‐associated protein, rather than DNA, under cellular conditions. Complex [(bis‐NHC)Pt(bt)]PF6 ( 1 a ; Hbt=1‐(3‐hydroxybenzo[b]thiophen‐2‐yl)ethanone) overcomes cisplatin resistance in cancer cells and displays significant tumor growth inhibition in mice with higher tolerable doses compared to cisplatin. The cellular Pt species shows little association with DNA, and localizes in the cytoplasm as revealed by nanoscale secondary ion mass spectrometry. An unbiased thermal proteome profiling experiment identified asparagine synthetase (ASNS) as a molecular target of 1 a . Accordingly, 1 a treatment reduced the cellular asparagine levels and inhibited cancer cell proliferation, which could be reversed by asparagine supplementation. A bis‐NHC‐ligated Pt species generated from the hydrolysis of 1 a forms adducts with thiols and appears to target an active‐site cysteine of ASNS. 相似文献
109.
Lok Kan Wu 《Phosphorus, sulfur, and silicon and the related elements》2017,192(9):1074-1077
An electrochemistry-based gravimetric method of analysis for the determination of thiosulfate concentrations in aqueous solutions and its application in chemical education are introduced. Nine standard aqueous thiosulfate solutions with triplicate concentrations of 0.02 M, 0.03 M, and 0.04 M were prepared in 1.0 M hydrochloric acid. The elemental sulfur produced in each sample was recovered by filtration, and the mass of the recovered elemental sulfur and the electrochemically determined equilibrium constant of the reaction at 25°C (Keq = 3.5) were used to determine the concentration of thiosulfate in each standard solution. The method % Error is 4.9 ± 3.0, which means that the average method % Error is less than 5.0. 相似文献
110.
Johnson Lui-Lui Tsai Taotao Zou Jia Liu Tianfeng Chen Anna On-Yee Chan Chen Yang Chun-Nam Lok Chi-Ming Che 《Chemical science》2015,6(7):3823-3830
Supramolecular interactions are of paramount importance in biology and chemistry, and can be used to develop new vehicles for drug delivery. Recently, there is a surge of interest on self-assembled functional supramolecular structures driven by intermolecular metal–metal interactions in cellular conditions. Herein we report a series of luminescent Pt(ii) complexes [Pt(C^N^Npyr)(CNR)]+ [HC^N^Npyr = 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine)] containing pincer type ligands having pyrazole moieties. These Pt(ii) complexes exert potent cytotoxicity to a panel of cancer cell lines including primary bladder cancer cells and display strong phosphorescence that is highly sensitive to the local environment. The self-assembly of these complexes is significantly affected by pH of the solution medium. Based on TEM, SEM, ESI-MS, absorption and emission spectroscopy, and fluorescence microscopy together with cell based assays, [Pt(C^N^Npyr)(CNR)]+ complexes were observed to self-assemble into orange phosphorescent polymeric aggregates driven by intermolecular Pt(ii)–Pt(ii) and ligand–ligand interactions in a low-pH physiological medium. Importantly, the intracellular assembly and dis-assembly of [Pt(C^N^Npyr)(CNR)]+ are accompanied by change of emission color from orange to green. These [Pt(C^N^Npyr)(CNR)]+ complexes accumulated in the lysosomes of cancer cells, increased the lysosomal membrane permeability and induced cell death. One of these platinum(ii) complexes formed hydrogels which displayed pH-responsive and sustained release properties, leading to low-pH-stimulated and time-dependent cytotoxicity towards cancer cells. These hydrogels can function as vehicles to deliver anti-cancer agent cargo, such as the bioactive natural products studied in this work. 相似文献