Preparation of Small‐Particle‐Size, Semiconductor CdS‐Doped Silica Glasses by the Sol–Gel Process

The sol–gel process has been applied successfully to the preparation of small‐particle‐size CdS‐doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of a complex solution of Si(OC 2 H 5 ) 4 and Cd(CH 3 COO) 2 ·2H 2 O were heated at 500°C, then reacted with H 2 S gas to form fine, hexagonal, CdS‐microcrystal‐doped glasses. The optical absorption edge is blue shifted by ∼0.4 eV compared with the bulk absorption value of CdS crystal. This result is interpreted in terms of a quantum‐confinement effect of small crystal size.