Stabilization of CdS Semiconductor Nanoparticles against Photodegradation by a Silica Coating Procedure

Miguel A Correa-Duarte, Michael Giersig, and Luis M Liz-Marzán

Chem. Phys. Lett., 1998, 286, 497–501

Nanometre-sized CdS semiconductor particles were synthesized in the presence of sodium citrate, and subsequently surrounded by a homogeneous silica shell. The coating procedure makes use of 3-(mercaptopropyl) trimethoxy silane (MPS) as a surface primer to deposit a thin silica shell in water. The dispersion is then transferred into ethanol, where thicker shells can be grown. The citrate-stabilized particles are slowly degraded through photochemical oxidation in the presence of dissolved oxygen. This destabilizing process is suppressed when a homogeneous, microporous silica shell is built up around the particles, through a limited access of O2 molecules to the CdS surface.