Photoluminescence and Raman Spectroscopy as Probes to Investigate Silver and Gold Dicyanide Clusters Doped in A-Zeolite and Their Photoassisted Degradation of Carbaryl

Abstract

Dicyanoaurate and dicyanoargentate ions doped in A-type zeolite were prepared and analyzed spectroscopically. Data from luminescence and Raman spectroscopies along with extended Huckel calculations indicate the formation of [M(CN)2-]n oligomers (M = Ag, Au) in the zeolite host. Variations in luminescent properties as a function of excitation wavelength, dopant concentration inside the zeolite host, and temperature facilitate assignment of cluster structures. The data obtained from a comparison of Ag- and Au-doped silica and γ-alumina show that the [M(CN)2-]n clusters form in the channels of the zeolite rather than on the surface. The [M(CN)2-]n clusters in A zeolite show strong catalytic activities toward the photodecomposition of carbaryl in aqueous solution. The photodecomposition of carbaryl at room temperature shows different decomposition products in the presence and absence of the M(CN)2- doped A zeolite catalyst. In addition, the decomposition rate constants increase as the metal content increases....