Stable silica-supported gold nanoparticles (Au NPs ) suitable for catalysis applications were conveniently obtained in a straightforward, one-step synthesis by simply adding an aqueous solution of HAuCl 4 to commercial polyethyleneiminefunctionalized silica beads (SiO 2 -PEI) as the only reactant without any external reducing agent and/or conventional stabilizing moieties. Six different types of Au NPs /(SiO 2 -PEI) beads termed Au x−y h, where x is the initial HAuCl 4 concentration (1, 5, or 10 mM) and y is the reaction time (1 or 24 h), were prepared and characterized by UV−vis diffuse reflectance spectroscopy, X-ray fluorescence, FE-SEM microscopy, and X-ray absorption spectroscopy. The SEM micrographs of Au x−y h samples showed that the particle size distribution decreases with the increase of the starting gold concentration, i.e., 70−100 nm for Au 1−x h, 40−70 nm for Au 5−x h, and Au 10−x h, whereas on passing from 1 to 24 h the aggregation phenomena overcome the nucleation ones, promoting the formation of bigger aggregates at the expense of small Au NPs . The XAS analysis as a combination of XANES and EXAFS studies provided detailed structural information regarding the coordination geometry and oxidation state of the gold atoms present on the beads. Moreover, the catalytic activity of the modified silica beads in the reduction of 4-nitrophenol to 4aminophenol by NaBH 4 was investigated and in one case the XAS analysis was repeated after recovery of the catalyst, demonstrating further reduction of the Au site to Au(0).

A novel, convenient method for the preparation of gold nanoparticles supported on alkyne-functionalized nanosilica is presented. Silica nanoparticles functionalized with alkynyl carbamate moieties (SiO 2 @Yne) were synthesized by co-condensation of the difunctional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) with tetraethoxysilane (TEOS) in an alkaline medium. The alkynylcarbamate functionalities present on silica are able to capture the gold precursor HAuCl 4 , spontaneously reduce it, and stabilize the resulting supported Au NPs , having an average size of ca. 11 nm. The prepared Au-SiO 2 @Yne was thoroughly analyzed by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), FT-IR, and UV−vis spectroscopy. The catalytic activity of Au-SiO 2 @Yne was investigated for the reduction of 4-nitrophenol to 4aminophenol by NaBH 4 , and kinetic constants k in the order of magnitude of about 10 −2 s −1 were found.

The reactions of 1,3,5-triaminobenzene derivatives with 2,3,4-trinitrothiophene and 2-bromo-3,4,5-trinitrothiophene gave new all-conjugated compounds bearing both an electron-withdrawing and an electron-donor moiety on the same unit. The reactions with 2,3,4-trinitrothiophene offered evidence, by NMR spectroscopy at low temperature, of the formation of new labile Wheland-Meisenheimer intermediates whereas at room temperature stable unexpected products derived from the attack of the nucleophile at C-4 with replacement of the nitro group were isolated. Their formation caused, in turn, the obtainment of a salt between 1-nitroso-2,4,6-triaminobenzenes and 2,4-dinitrothiophen-3-ol. The reactions with 2-bromo-3,4,5-trinitrothiophene produced in good yields the SNAr substitution product with the displacement of the bromide. All the new coupling products obtained are of applicative interest, considering the increasing concern for highly conjugated π-systems in solar energy conversion or optoelectronic devices.

A new, simple and convenient approach to prepare silver nanoparticles supported on SiO2–PEI composites for the decoloration of organic dyes.

A combined X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methodology is here presented on a series of partially and fully reduced Au(III) samples. This allows monitoring the relative fraction of Au(III) and Au(0) in the studied samples, displaying a consistent and independent outcome. The strategy followed is based, for the first time, on two structural models that can be fitted simultaneously, and it evaluates the correlation among strongly correlated parameters such as coordination number and the Debye-Waller factor. The results of the present EXAFS and XANES approach can be extended to studies based on X-ray absorption spectroscopy experiments for the in situ monitoring of the formation of gold nanoclusters.