2 research outputs found
Influence of the hydrolysis and condensation time on the preparation of hybrid materials
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 organicâinorganic matrix produced by the
solâgel 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 CiĂȘncia 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 QuĂmica [project F-COMP-01-0124-FEDER-022716 (ref. FCT Pest-C/Qui/UI0686/2011)-FEDER-COMPETE] and Centro de FĂsica (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