The CdS nanostructure undergoes photochemical dissolution, and hence, the photocatalytic activity deteriorates with light irradiation time. A thin layer of silica coating over CdS surface may prevent the photo-corrosion and coalescence of quantum size CdS particles. Hence, we synthesized SiO2@CdS nanocomposites of different shapes and characterized them by XRD, HRTEM, EDX, SAED, BET surface area measurement and absorption and emission study. The dispersion of spherical CdS (Cd-2.62 at% and S-2.33 at%) nanoparticles of cubic crystal structure into thick amorphous SiO2 (43.79 at%) matrix is demonstrated here. The fabrication of core (CdS)-shell (SiO2) structure (SiO2@CdS) consisting of CdS nanorod (Cd-19.79 at% and S-22.90 at%) core (length similar to 126 nm and width similar to 6 nm) having characteristic lattice fringes of hexagonal crystals and thin SiO2 (12.81 at%) shell (thickness = 1-1.4 nm) is successfully achieved for the first time. The surface area (21.2 m(2)/g) of CdS nanorod (aspect ratio = 21) is found to increase (42.3 m(2)/g) after SiO2 coating. The photoluminescence of CdS nanosphere (485 nm) and nanorod (501 nm) is highly quenched after SiO2 layer formation. The superior photocatalytic activity of SiO2@CdS composites for the benzaldehyde oxidation under UV irradiation has been displayed. (C) 2011 Elsevier Inc. All rights reserved.