Spectral and adsorption characteristics of Au(III) and Au(0) composite materials

• Published in: Protection of metals and physical chemistry of surfaces Vol. 49; no. 4; pp. 408 - 412
• Main Authors: Zubareva, N. A., Khokhlova, T. D.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-07-2013; Springer Nature B.V
• Subjects: Absorption spectra; Adsorption; Aluminum oxide; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composite materials; Corrosion and Coatings; Gold; Industrial Chemistry/Chemical Engineering; Infrared spectra; Inorganic Chemistry; Materials Science; Metallic Materials; Oxides; Physicochemical Processes at the Interfaces; Spectra; Surface chemistry; Tribology; Aluminum Oxide Specimen; AuCl; Gold Atom; Aerosil; Chloroauric Acid
• ISSN: 2070-2051; 2070-206X
• DOI: 10.1134/S2070205113040175

The adsorption of HAuCl
4
chloroauric acid on silica modified with γ-aminopropyltriethoxysilane (aminosilica) and on aluminum oxide is studied. Diffuse-scattering spectra of these Au(III) composite materials and their reduced Au(0) composites are recorded in the visible and infrared spectral ranges. Au(III) composites are selective with respect to the adsorption of phenylacetylene (PA) from octane due to the formation of π-complexes with Au(III). Au(III)-aluminum oxide composite material has a much larger capacity for PA adsorption than does aminosilica composite with the same gold content. The formation of coordination bonds between free aminopropyl groups of the silica carrier and gold atoms prevents PA adsorption. The formation of such bonds is manifested in a shift in λ
max
of the spectral line from 408 to 522 and 546 nm with a decrease in [Au(III)] concentration from 400 to 120 and 60 μmol/g. The decrease in the intensity and the red shift of the absorption bands of NH
2
stretching vibrations in the infrared spectra of the specimen upon modification also confirms the supposition. There are absorption bands of free hydroxyl radicals, but no band of bound radicals in the infrared spectra of Au(0) composites. The electronic spectra (λ
max
= 511, 504, and 512 nm) are close for all three specimens that differ in gold content, which means that the sizes of immobilized Au(0) nanoparticles are similar. Upon the sorption of HAuCl
4
on a Au(III)-aluminum oxide specimen, the absorption band of surface OH groups disappears, however, in Au(0) composite, it appears again near 3105 cm
−1
.