Synthesis and characterization of organic-inorganic hybrid materials prepared by sol-gel and containing CdS nanoparticles prepared by a colloidal method using poly(N-vinyl-2-pyrrolidone)

This paper describes the synthesis and characterization of CdS nanoparticles (NPs) stabilized with poly(N-vinyl-2-pyrrolidone) and their further immobilization on a hybrid organic–inorganic matrix produced by the sol–gel process. The production of the hybrid matrix doped with CdS NPs was carried out in two steps. In the first step a precursor, designated diureasil precursor, was synthesized from the reaction between the terminal amine groups of a,x-diamine-poly(oxyethylene-co-oxypropylene) and the isocyanate group of 3-isocyanatopropyltriethoxysilane. The next step involved the hydrolysis and condensation reactions of ethoxy groups attached to silicon, this step resulting in the formation of a crosslinked siliceous network linked through urea bonds to a poly(oxyethylene)/ poly(oxypropylene) chain. The NPs were added to the diureasil precursor before the gelation process to allow a homogeneous dispersion of the NPs within the matrix. The developed method allowed the transfer of colloidal NPs to a solid matrix without the need of exchange the capping agents or the solvent. The materials were characterized by absorption, steady-state photoluminescence spectroscopy and by TEM. The results obtained showed the presence of CdS NPs with quantum size effect dispersed within the diureasil matrix. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the NPs within the matrix. The TEM analysis confirmed that the NPs are uniformly dispersed within the diureasil matrix.This work has been partially supported by the Fundação para a Ciência e a Tecnologia (FCT). L. F. Gonçalves thanks the FCT for the PhD grant SFRH/BD/38262/2007. The authors gratefully acknowledge the financial support by Centro de Química [project F-COMP-01-0124-FEDER-022716 (ref. FCT Pest-C/Qui/UI0686/2011)-FEDER-COMPETE] and Centro de Física (Universidade do Minho). The authors would like to thank the Electron Microscope Unit of the Mark Wainwright Analytical Centre at The University of New South Wales, for scientific and technical support