CdS@NbxOy),core-shell nanostructures were used as heterogeneous catalysts for oxidizing organic compounds in aqueous media under ultraviolet light. The core/shell nanocrystals contained two nano-structured semiconductor that enhanced the catalytic properties of the material under UV-Vis irradiation. The developed core/shell nanocrystals displayed significant catalytic activity during the oxidation of organic substrates and may be suitable for degrading organic pollutants in water. The ESI-MS spectrum obtained for methylene blue after exposure to the nanostructured semiconductor nanoparticles revealed a hydroxylation caused by hydroxyl radicals in solution, forming a species at m/z= 301. (c) 2014 Elsevier B.V. All rights reserved.