Growth and characterization of ZnS and ZnCdS nanoclusters in mordenite zeolite host

The growth of semiconductor nanoclusters of ZnS and the ternary ZnCdS system embedded in synthetic mordenites by ionic exchange using different mixtures of CdCl(2) and ZnCl(2) as starting sources, followed by treatment in hydrogen sulphide flow, is reported. Compositional, morphological and structural studies were realized by XRD, SEM, TEM and energy dispersive spectroscopy (EDS). XRD shows well-crystallized mordenite and the absence of secondary phases; EDS gives us the chemical composition of the matrix host and the relative weight percent of Cd, Zn and S. TEM and SEM show the morphology, packing and sizes of mordenite crystals (bundled needles of 3 mum long and 0.07 mum width). Measurements of the absorption spectra by diffuse reflectance spectroscopy in the UV-visible range allow us an analysis of the optical behavior as a function of the relative concentration of Zn and Cd. Samples show blue shifts in the absorption edges when the Cd concentration decreases and correspondingly, the Zn concentration increases. The optical band gap is determined and its behavior with concentration changes is discussed. Previously, ZnCdS clusters supported on mordenite were prepared in our laboratory by hydrothermal growth. A comparative discussion of the results obtained through both synthetic processes is presented. (C) 2003 Elsevier B.V. All rights reserved.