Nanocomposites of CdS Nanocrystals with Montmorillonite Functionalized with Thiourea Derivatives and Their Use in Photocatalysis

Nanocomposites of CdS were prepared in refluxing DMF using a montmorillonite organofunctionalized with thiourea derivatives, with different proportions of the matrix relative to Cd²⁺ ions. The matrix provided sulfur atoms for CdS formation as well as specific binding sites for systematic anchoring of the nanocrystals. However, addition of thiourea to the reaction medium was required in order to yield cubic CdS nanocrystals, and increasing the thiourea/Cd²⁺ molar ratio led to the formation of mixtures of cubic and hexagonal CdS. The samples obtained using a thiourea/Cd²⁺ ratio of 2, with cubic CdS, exhibited photoluminescence due to both direct recombination and surface trap states. The distribution of CdS throughout the matrix was characterized by the presence of aggregates (with diameters in the region of 50 nm) of nanocrystals (with diameters less than 7 nm) on the outer surface as well as small pillars in the interlayer region. The photocatalytic performance of the nanocomposites was tested in the degradation of Rhodamine 6G under sunlight irradiation, with promising results in terms of degradation time and degree of mineralization