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81.
This Concept article provides an elementary discussion of a special class of large‐sized gold compounds, so‐called Au nanoclusters, which lies in between traditional organogold compounds (e.g., few‐atom complexes, <1 nm) and face‐centered cubic (fcc) crystalline Au nanoparticles (typically >2 nm). The discussion is focused on the relationship between them, including the evolution from the Au???Au aurophilic interaction in AuI complexes to the direct Au? Au bond in clusters, and the structural transformation from the fcc structure in nanocrystals to non‐fcc structures in nanoclusters. Thiolate‐protected Aun(SR)m nanoclusters are used as a paradigm system. Research on such nanoclusters has achieved considerable advances in recent years and is expected to flourish in the near future, which will bring about exciting progress in both fundamental scientific research and technological applications of nanoclusters of gold and other metals. 相似文献
82.
83.
Kuai L Geng B Wang S Zhao Y Luo Y Jiang H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(12):3482-3489
Much effort has gone into generating polyhedral noble metal nanostructures because of their superior electrocatalytic activities for fuel cells. Herein, we report uniform, high-yield icosahedral silver and gold nanoparticles by using a facile one-pot, seedless, water-based approach that incorporates polyvinyl pyrrolidone and ammonia. Electrocatalysis of the oxygen-reduction reaction was carried out in alkaline media to evaluate the performance of the icosahedral nanoparticles. They showed excellent stability and much higher electrocatalytic activity than the spherelike nanoparticles; they display a positive shift in reduction peak potential for O(2) of 0.14 and 0.05 V, while the reduction peak currents of the silver and gold icosahedra are 1.5- and 1.6-fold, respectively, better than the spherelike nanoparticles. More importantly, the icosahedral nanoparticles display electrocatalytic activities comparable with commercial Pt/C electrocatalysts. The facile preparation of icosahedral silver and gold nanoparticles and their superior performance in the oxygen reduction reaction render them attractive replacements for Pt as cathode electrocatalysts in alkaline fuel cells. 相似文献
84.
In the present study, the flow-through silica, featured with hierarchical pores, i.e., tunable mesopores and penetrable macropores, was attempted as the chromatographic stationary phase matrix to immobilize gold nanoparticles (AuNPs). It was first modified by mercapto groups (named as SiO2-SH), and then by AuNPs (named as SiO2-S-Au). Thanks to the characteristic macropores, the column backpressure of SiO2-S-Au was comparable to SiO2-SH, which effectively overcame the difficulty of high column backpressure upon the nanoparticles were introduced to the chromatographic matrix. Both the reversed-phase and hydrophilic interaction liquid chromatographic performance were observed on these two columns but with different selectivities. Hydrophobic, hydrophilic, hydrogen bond and electrostatic interactions between the SiO2-S-Au stationary phase and analytes could contribute to the retention. The SiO2-S-Au column showed excellent aqueous compatibility by “Stop-flow” test with the relative standard deviations (RSD) of analyte’s k (capacity factor) values from 0.59% to 2.88%. The reproducibility of SiO2-S-Au was acceptable with RSDs of analyte’s k values in the range of 3.13%-5.03%. In addition, compared with the SiO2-SH column, the SiO2-S-Au column had better separation performance and selectivity. The results demonstrated that the flow-through silica was a promising matrix for nanoparticles with low backpressure and different selectivities. 相似文献
85.
86.
Dr. Peng Liu Prof. Dr. Can Li Prof. Dr. Emiel J. M. Hensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12122-12129
Efficient basic hydrotalcite (HT)‐supported gold nanoparticle (AuNP) catalysts have been developed for the aerobic oxidative tandem synthesis of methyl esters and imines from primary alcohols catalyzed under mild and soluble‐base‐free conditions. The catalytic performance can be fine‐tuned for these cascade reactions by simple adjustment of the Mg/Al atomic ratio of the HT support. The one‐pot synthesis of methyl esters benefits from high basicity (Mg/Al=5), whereas moderate basicity greatly improves imine selectivity (Mg/Al=2). These catalysts outperform previously reported AuNP catalysts by far. Kinetic studies show a cooperative enhancement between AuNP and the surface basic sites, which not only benefits the oxidation of the starting alcohol but also the subsequent steps of the tandem reactions. To the best of our knowledge, this is the first time that straightforward control of the composition of the support has been shown to yield optimum AuNP catalysts for different tandem reactions. 相似文献
87.
Sara Sabater Jose A. Mata Eduardo Peris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6380-6385
A triazolyl‐di‐ylidene ligand has been used for the preparation of a homodimetallic complex of gold, and a heterodimetallic compound of gold and iridium. Both complexes have been fully characterized and their molecular structures have been determined by means of X‐ray diffraction. The catalytic properties of these two complexes have been evaluated in the reduction of nitroarenes by transfer hydrogenation using primary alcohols. The two complexes afford different reaction products; whereas the AuI–AuI catalyst yields a hydroxylamine, the IrIII–AuI complex facilitates the formation of an imine. 相似文献
88.
Sheng Wang Prof. Dr. Wei Chen Prof. Dr. Ai‐Lin Liu Lei Hong Hao‐Hua Deng Prof. Xin‐Hua Lin 《Chemphyschem》2012,13(5):1199-1204
The origin of the peroxidase‐like activity of gold nanoparticles and the impact of surface modification are studied. Furthermore, some influencing factors, such as fabrication process, redox property of the modifier, and charge property of the substrate, are investigated. Compared to amino‐modified or citrate‐capped gold nanoparticles, unmodified gold nanoparticles show significantly higher catalytic activity toward peroxidase substrates, that is, the superficial gold atoms are a contributing factor to the observed peroxidase‐like activity. The different catalytic activities of amino‐modified and citrate‐capped gold nanoparticles toward 3,3′,5,5′‐tetramethylbenzidine (TMB) and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) show that the charge characteristics of the nanoparticles and the substrate also play an important role in the catalytic reactions. 相似文献
89.
Kristen E. Snell Dr. Hossein Ismaili Prof. Dr. Mark S. Workentin 《Chemphyschem》2012,13(13):3185-3193
Photolysis of organic solvent soluble aryl azide‐modified gold nanoparticles (N3‐AuNPs) with a core size of 4.6±1.6 nm results in the generation of interfacial reactive nitrene intermediates. The high reactivity of the nitrenes is utilized to tether the AuNP to the native surface of carbon nanotubes, and reduce graphene oxide and micro‐diamond powder, likely via addition to π‐conjugated carbon skeleton or insertion into the functionalities at the surface, to yield the desired hybrid material without the need for pretreatment of the surface. The AuNP‐covalent hybrid materials are robust in that they survive vigorous washing and sonication. In the absence of photolysis no attachment occurs with the same N3‐AuNP. The nanohybrid AuNP‐nanohybrid materials are characterized using a combination of TEM, powder XRD, XPS and UV/Vis and IR spectroscopies. All of the characterization studies confirm the uniform incorporation of the AuNP on the irradiated substrates. 相似文献
90.
Prof. Dr. Han Myoung Lee Prof. Dr. Kwang S. Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13203-13207
Since gold clusters have mostly been studied theoretically by using DFT calculations, more accurate studies are of importance. Thus, small neutral and anionic gold clusters (Aun and Aun?, n=4–7) were investigated by means of coupled cluster with singles, doubles, and perturbative triple excitations [CCSD(T)] calculations with large basis sets, and some differences between DFT and CCSD(T) results are discussed. Interesting isomeric structures that have dangling atoms were obtained. Structures having dangling atoms appear to be stable up to n=4 for neutral gold clusters and up to n=7 for anionic clusters. The relative stabilities and electronic properties of some isomers and major structures are discussed on the basis of the CCSD(T) calculations. This accurate structure prediction of small gold clusters corresponding to experimental photoelectron spectral peaks is valuable in the field of atom‐scale materials science including nanocatalysts. 相似文献