GROWTH AND REACTIVITY OF ZINC AND CADMIUM-OXIDE NANO-PARTICLES IN ZEOLITES

Zinc and cadmium oxide particles in the size range of 1-10 nm grow ins ide a faujasite matrix, zeolites X and Y or its hexagonal analogue EMT starting from metal ion-exchanged zeolites subjected (i) to sodium hy droxide solutions (0.01-0.75 M) at elevated temperatures (293-353 K) a nd (ii) to subsequent calcination in air at 673 K. The oxide nano-part icles are accommodated in mesopores forming simultaneously with the pr ecipitation of the metal hydroxides. As revealed by adsorption measure ments the maximum diameters and the overall volumes of the mesopores g row with increasing concentration of the lye used for the precipitatio n. The main portion of mesopores is formed as bubbles inside the zeoli te matrix, only a small fraction as pockets at the outer surface of th e zeolite crystallites. The embedded oxide nano-particles are physical ly and chemically uniform, i.e. they show (i) the expected quantum siz e effects in the diffuse reflectance spectra and (ii) a particle size effect concerning the reversible formation of cadmium carbonate.