N-doped carbon xerogels were obtained from organic xerogels prepared using different N-containing organic compounds, including 3-hydroxy aniline, melamine, and 3-hydroxy pyridine. Carbonization was carried out between 500 and 900 degreeC. The surface chemistry of samples was determined by elemental analysis and X-ray photoelectron spectroscopy, their porous texture was determined by N2 and CO2 adsorption at (-)196 and 0degreeC, respectively, and their morphology was determined by scanning electron microscopy. N-doped carbon xerogels with a wide variety of N contents and functionalities were obtained according to the ingredients and carbonization temperature used. Carbon xerogels contained, in different proportions, three/four N functionalities: pyridinic, pyrrolic and/or pyridonic, and quaternary N functionalities. They were microporous carbons with narrow micropores that had constrictions at their entrances, producing higher CO2(-) than N2-determined micropore surface areas. Morphology studies showed samples to be constituted by isolated microspheres or microsphere clusters. Microsphere diameters depended on the recipe and carbonization temperature used.

No abstract

No abstract

Gold nanoparticles have been deposited on three kinds of carbon nanotubes (CNTs), including nitrogen‐doped CNTs, by three different methods, namely, impregnation, organometallic decomposition, and deposition–precipitation. The choice of the gold precursor, the support, and the preparation procedure is critical for the control of the size and location (on or inside the nanotubes) of the gold nanoparticles. These catalysts were tested for the selective oxidation of CO in a hydrogen‐rich atmosphere. We have shown that the use of nitrogen‐doped CNTs as a support permits one to reach much higher activity and selectivity at low temperaturethan with the other CNT supports. This catalyst also shows a good stability under reaction conditions without detectable sintering.

Acetone solutions of [Au(OClO3)(PCy3)] react with complexes [M{S2C=(t-Bu-fy)}2]2- [t-Bu-fy=2,7-di-tert-butylfluoren-9-ylidene; M=Pd (2a), Pt (2b)] or [M{S2C=(t-Bu-fy)}(dbbpy)] [dbbpy=4,4'-di-tert-butyl-2,2'-bipyridyl; M=Pd (3a), Pt (3b)] to give the heteronuclear complexes [M{S2C=(t-Bu-fy)}2{Au(PCy3)}2] [2:1 molar ratio; M=Pd (4a), Pt (4b)], [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}]ClO4 [1:1 molar ratio; M=Pd (5a), Pt (5b)], or [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}2](ClO4)2 [2:1 molar ratio; M=Pd (6a), Pt (6b)]. The crystal structures of 3a, 4a, 4b, 5b, and 6a have been solved by single-crystal X-ray studies and, in the cases of the heteronuclear derivatives, reveal the formation of short Pd...Au or Pt...Au metallophilic contacts in the range of 3.048-3.311 A. Compounds 4a and b and 5a and b undergo a dynamic process in solution that involves the migration of the [Au(PCy3)]+ units between the sulfur atoms of the dithiolato ligands. The coordination of 2a and b and 3a and b to [Au(PCy3)]+ units results in important modifications of their photophysical properties. The dominant effect in the absorption spectra is an increase in the energy of the MLCT (4a and b) or charge transfer to diimine (5a, b, 6a, b) transitions because of a decrease in the energies of the mixed metal/dithiolate HOMOs. The Pd complexes 2a and 4a are luminescent at 77 K, and the features of their emissions are consistent with an essentially metal-centered 3d-d state. The Pt/Au complexes are also luminescent at 77 K, and their emissions can be assigned as originating from a MLCT triplet state (4b) or a mixture of charge transfer to diimine and diimine intraligand pi-pi* triplet states (5b and 6b).