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171.
Navjeet Kaur Pooja Grewal Pranshu Bhardwaj Meenu Devi Neha Ahlawat Yamini Verma 《合成通讯》2013,43(22):3058-3100
The heterocyclic chemistry field has been revolutionized using transition metal catalyst in recent years. Various research groups have focused on the development of general protocols to achieve better functional group compatibilities and greater levels of molecular complexity under mild reaction conditions using easily available starting substrates. These methods afford many advantages as compared to alternative pathways involved in the synthesis of heterocyclic compounds. In this review article, we have concentrated on the synthesis of nitrogen-containing five-membered heterocylces in the presence of silver catalyst. 相似文献
172.
This paper describes the oxidation of benzylic and allylic alcohols under non-aqueous and aprotic conditions or microwave conditions using benzyltriphenylphosphonium chlorochromate (1) PhCH2PPh3CrO3.HCl which has been prepared by mixing an aqueous solution of benzyltriphenylphosphonium chloride with CrO3 in 6 N HCl at room temperature. This reagent is stable orange powder which may be stored for months without loss of its activity. This compound is readily soluble in organic solvents such as acetonitrile, chloroform and dichloromethane and slightly soluble in carbon tetrachloride, ether and hexane. the oxidation under microwave conditions is much more faster. 相似文献
173.
Mekhman S. Yusubov Elena N. Tveryakova Elena A. Krasnokutskaya Irina A. Perederyna Viktor V. Zhdankin 《合成通讯》2013,43(8):1259-1265
A simple and environmentally safe general method of iodination of aromatic substrates under sovent‐free conditions using the I2/AgNO3 combination in a solid state is reported. Both activated and deactivated aromatic compounds afford the respective aryl iodides in generally high yields (80–90%). 相似文献
174.
Silver nanolayers sputtered on polytetrafluoroethylene and their changes induced by post‐deposition annealing at 100–300 °C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy and by measurement of electrical sheet resistance by two‐point technique. Chemical composition was determined by X‐ray photoelectron spectroscopy (XPS) and electrokinetic analysis in dependence on the gold layer thickness. The annealing at 300 °C leads to significant rearrangement of the silver layer, and the transition threshold increases to 35 nm. The presence of oxidized structures on silver‐coated samples is observed in XPS spectra and by electrokinetic analysis, too. Annealing of pristine and silver‐coated poly(tetrafluoroethylene) at 300 °C results in significant change of the sample surface morphology and chemistry. There is observed formation of isolated silver islands on the surface, which could be connected with silver melting. Later, the silver agglomeration takes place. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
175.
Lenka Škantárová Andrej Oriňák Renáta Oriňáková Monika Jerigová Monika Stupavská Dušan Velič 《Surface and interface analysis : SIA》2013,45(8):1266-1272
Present article deals with functionality of silver nanostructured surfaces prepared by potentiostatic electrochemical deposition on the paraffin impregnated graphite electrode as template‐free substrates. The effect of the electrodeposition conditions on two silver surface functions: analytical signal enhancement in Surface‐enhanced Raman spectroscopy and pre‐ionization function, applied in secondary ion mass spectrometry (SIMS) is reported. Functional silver nanostructured substrate was prepared at a potential ?850 mV with a deposition duration of 20 min. Analytical signal enhancement factors of 3.2 ×105 for Raman peak at 649 cm?1, 3.0×105 for peak at 810 cm?1 and 2.7×105 for peak at 1539 cm?1 were determined for Rhodamine 6G at deposited surface. Slight pre‐ionization effect has been observed in SIMS, and 1.2×105 fold signal enhancement was established for fragment of Rhodamine 6G with m/z 429 (M‐CH3‐Cl). Electrochemical preparation of nanostructures represents a step towards surface integration directly into miniaturized systems and sensors. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
176.
Silver nanoparticles enhanced glucose oxidase electrodes were prepared on the basis of chitosan matrix. The enzyme electrodes exhibited high sensitivity and excellent response performance to glucose with a linear range from 1×10?6 to 8×10?3 mol · L?1. And the time reaching the steady‐state amperometric response was less than 5 seconds. The inhibition percentage of this enzyme electrode against copper ions concentration was linear ranging from 1.2×10?6 to 5×10?5 mol · L?1. These properties of enzyme electrodes are probably due to the excellent electron transfer of silver nanoparticles and the orientation of glucose oxidase molecule. 相似文献
177.
Laurent Mirolo Tobias Schmidt Dr. Sonja Eckhardt Prof. Dr. Markus Meuwly Prof. Dr. Katharina M. Fromm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1754-1761
Artificial implants and biomaterials lack the natural defense system of our body and, thus, have to be protected from bacterial adhesion and biofilm formation. In addition to the increasing number of implanted objects, the resistance of bacteria is also an important problem. Silver ions are well‐known for their antimicrobial properties, yet not a lot is known about their mode of action. Silver is expected to interact on many levels, thus the development of silver resistance is very difficult. Nevertheless, some bacteria are able to resist silver, even at higher concentrations. One such defense mechanism of bacteria against heavy‐metal intoxication includes an efflux system. SilE, a periplasmic silver‐binding protein that is involved in this defense mechanism, has been shown to possess numerous histidine functions, which strongly bind to silver atoms, as demonstrated by ourselves previously. Herein, we address the question of how histidine binds to silver ions as a function of pH value. This property is important because the local proton concentration in cells varies. Thus, we solved the crystal structures of histidine–silver complexes at different pH values and also investigated the influence of the amino‐acid configuration. These results were completed by DFT calculations on the binding strength and packing effects and led to the development of a model for the mode of action of SilE. 相似文献
178.
Sun Hye Hwang Jongmin Roh Prof. Dr. Jyongsik Jang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(39):13120-13126
Enhanced harvesting of visible light is vital to the development of highly efficient dye‐sensitized solar cells (DSSCs). Nanosilver‐decorated TiO2 nanofibers (Ag@TiO2 NFs) were synthesized by depositing chemically reduced Ag ions onto the surface of electrospun TiO2 nanofibers (TiO2 NFs). The prepared Ag@TiO2 NFs were coated with SiO2 (SiO2@Ag@TiO2 NFs) by using PVP as coupling agent for protecting corrosion of Ag nanoparticle by I?/${{\rm I}{{- \hfill \atop 3\hfill}}}$ solution. The fabricated SiO2@Ag@TiO2 NFs demonstrated a synergistic effect of light scattering and surface plasmons, leading to an enhanced light absorption. Moreover, an anode consisting of SiO2@Ag@TiO2 NFs incorporating TiO2 nanoparticles (NPs) increased light harvesting without substantially sacrificing dye attachment. The power conversion efficiency increased from 6.8 to 8.7 % for a thick film (10 μm), that is, 28 %. These results suggest that SiO2@Ag@TiO2 NFs are promising materials for enhanced light absorption in dye‐sensitized solar cells. 相似文献
179.
Dr. Qiu‐Feng Lü Jia‐Yin Zhang Jun Yang Zhi‐Wei He Prof. Dr. Chang‐Qing Fang Qilang Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):10935-10944
Self‐assembled poly(N‐methylaniline)–lignosulfonate (PNMA–LS) composite spheres with reactive silver‐ion adsorbability were prepared from N‐methylaniline by using lignosulfonate (LS) as a dispersant. The results show that the PNMA–LS composite consisted of spheres with good size distribution and an average diameter of 1.03–1.27 μm, and the spheres were assembled by their final nanofibers with an average diameter of 19–34 nm. The PNMA–LS composite spheres exhibit excellent silver‐ion adsorption; the maximum adsorption capacity of silver ions is up to 2.16 g g?1 at an adsorption temperature of 308 K. TEM and wide‐angle X‐ray results of the PNMA–LS composite spheres after absorption of silver ions show that silver ions are reduced to silver nanoparticles with a mean diameter of about 11.2 nm through a redox reaction between the PNMA–LS composite and the silver ions. The main adsorption mechanism between the PNMA–LS composite and the silver ions is chelation and redox adsorption. In particular, a ternary PNMA–LS–Ag composite achieved by using the reducing reaction between PNMA–LS composite spheres and silver ions can be used as an antibacterial material with high bactericidal rate of 99.95 and 99.99 % for Escherichia coli and Staphylococcus aureus cells, respectively. 相似文献
180.
Dr. Sam C. K. Hau Prof. Dr. Thomas C. W. Mak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5387-5400
Single‐crystal X‐ray diffraction of a series of ten crystalline silver(I)–trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a vinyl substituent, provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co‐existence of different types of silver(I)–carbon bonding interactions (silver–ethynide, silver–ethynyl, silver–ethenyl, and silver–aromatic) on the construction of coordination networks that were consolidated by argentophilic and weak inter/intramolecular interactions. The complex Ag L10? 6 AgCF3CO2 ? H2O ? MeOH ( HL10 =1‐{[4‐(prop‐2‐ynyloxy)‐3‐vinylphenyl]ethynyl}naphthalene) is the first reported example that exhibits all four kinds of silver(I)–carbon bonding interactions in the solid state. 相似文献