One-pot synthesis of CdS nanoparticles in the channels of mesosructured silica films and monoliths

Abstract

Cd(II)-modified mesoporous silica films and/or monoliths synthesized in one pot using a true liquid crystalline (TLC) approach have been reacted with H2S gas to produce CdS-modified mesostructured nanocomposite materials (Nano-CdS/meso-SiO2). During this process, both the TLC and the metallotropic liquid crystalline (MLC) mesophase of metal salt (Cd(H 2O)42)-nonionic surfactant (CnH2n+1- (OCH2CH2)mOH, CnEOm) systems were collectively used to incorporate large quantities of metal ions into the mesoporous silica film and monoliths. The effect of the cadmium nitrate concentration on the formation and structure of the mesoporous silica has also been investigated. The results show that at low salt concentrations, the mesoporous silica is anisotropic (hexagonal); however, at high salt concentration, the structure is isotropic (cubic or disordered). The freshly prepared CdS nanoparticles are reactive toward the surface acids that form during the H2S treatment. These surface acids also promote the degradation of the CdS nanopaticles. However, the CdS particles in the mesopores can be stabilized by washing out the acid sides or aging the samples for a period of time before the H2S reaction. The optical absorption edge of the CdS nanoparticle in the pores is sensitive to the composition and structure of the host. In this context, the materials were characterized using FTIR, micro-Raman, UV-visible absorption spectroscopy, POM, TEM, and PXRD techniques.