Au clusters smaller than 1.5 nm and stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) showed higher activity for aerobic oxidation of alcohol than those of larger size or stabilized by poly(allylamine) (PAA). X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of adsorbed CO, and X-ray absorption near edge structure measurements revealed that the catalytically active Au clusters are negatively charged by electron donation from PVP, and the catalytic activity is enhanced with increasing electron density on the Au core. Based on similar observations of Au cluster anions in the gas phase, we propose that electron transfer from the anionic Au cores of Au:PVP into the LUMO (pi*) of O(2) generates superoxo- or peroxo-like species, which plays a key role in the oxidation of alcohol. On the basis of these results, a simple principle is presented for the synthesis of Au oxidation catalysts stabilized by organic molecules.

Gold nanoparticles (<2 nm) stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP NPs) were prepared by reduction of AuCl4- with NaBH4 in the presence of PVP and characterized via an array of methods including optical absorption spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray absorption near-edge structure, extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy. We demonstrate for the first time that the Au:PVP NPs act as catalyst toward homocoupling of phenylboronic acid in water under aerobic conditions. Suppression of biphenyl formation under anaerobic conditions indicates that molecular oxygen dissolved in water is intimately involved in the coupling reactions. A mechanism of the aerobic homocoupling catalyzed by the Au:PVP NPs is proposed on the basis of a crucial role of dissolved oxygen, steric effects on the product yields, and the well-established mechanism for the Pd(II)-based catalysts.

A gold cluster, Au(41)(S-Eind)(12), was synthesized by ligating the bulky arenethiol 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacene-4-thiol (Eind-SH) to preformed Au clusters. Extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, and the fragmentation pattern in the mass spectrometry analysis indicated that formation of gold-thiolate oligomers at the interface was suppressed, in sharp contrast to conventional thiolate-protected Au clusters.

Small PVP-stabilized gold clusters were successfully prepared by the homogeneous mixing of continuous flows of aqueous AuCl 4 (-) and BH 4 (-) in a micromixer. Spectroscopic characterization revealed that microfluidic synthesis could yield monodisperse Au:PVP clusters with an average diameter of approximately 1 nm, which is smaller than clusters produced by conventional batch methods. These approximately 1 nm Au:PVP clusters exhibited higher catalytic activity for the aerobic oxidation of p-hydroxybenzyl alcohol than did Au:PVP clusters prepared by batch methods.

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N(2) adsorption at 77 K, thermogravimetry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N(2) adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.

The crystalline carbon nanotubes having mesopores that are open at one end, with pore width of 4 ( 0.8 nm, were characterized by XRD, XPS, and HRTEM. The N 2 adsorption isotherm of multiwall carbon nanotubes was measured at 77 K. A hump was observed near P/P 0 ) 0.4 in the adsorption isotherm. The adsorption isotherm was deconvoluted into those on the inner and external surfaces using the separately determined total, inner, and external surface areas. The adsorption isotherm on the inner surface was without adsorption hysteresis and had a sharp uptake at the P/P 0 region corresponding to the mesopore width, which was ascribed to capillary condensation in the mesopores of carbon nanotubes.

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Organogold clusters Au 54 (C 2 Ph) 26 were selectively synthesized by reacting of polymer-stabilized Au clusters (1.2±0.2 nm) with excess phenylacetylene in chloroform.Recent studies have shown that gold clusters protected by ligands (phosphines and thiolates) exhibit unique optical, 10 electrochemical, magnetic, and catalytic properties. 1-7 Such ligand-protected Au clusters have poteintial applications in diverse fields including catalysis, 7-9 nanoscale electronics, 10-16 drug delivery, 17 molecular biology, 18-20 and surface patterning. 21,22 State-of-the-art precision synthesis, theoretical 15 calculations, and single-crystal structure determination have shown that the novel properties of these clusters are associated with cluster substructures, namely the Au core, the ligands, and their interface. Therefore, to design and tune the properties of ligand-protected Au clusters, it is crucial to control the structures 20 of individual substructures; specifically the number of constituent atoms and the geometric structure of the Au core, the interfacial structure between the Au core and the ligands, and the physicochemical properties of the ligands.In this regard, an interesting challenge is to produce new