Silica Nanoparticles, Synthesis, Modification And Their Applications In The Fabrication Of Polypyrrolebased Silica Nanocomposites
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Date
2010-03
Authors
Mohammad, Jafarzadeh
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
A modified preparation of silica nanoparticles via sol-gel process is described. The
ability to control the particle size and distribution is found to be highly dependent on
mixing modes of the reactants and drying techniques. The mixture of tetraethoxysilane
(TEOS) and ethanol followed by addition of water (Mode-A) produce monodispersed
powder with an average particle size of 10.6 ± 1.40 nm and a narrow size distribution.
The freeze drying technique (FD) further improves the quality of the powder compared
to heat drying (HD). The powder consists of a well-order structure of silica
nanoparticles with low shrinkage, bigger pore size and volume and large endothermic
enthalpies (ΔHFD = - 688 J g-1 vs. ΔHHD = - 617 J g-1), leading to easy escape of
physically adsorbed water. Then, an easy and swift pathway in the preparation of
organo-modified silica in nanosize range with amine terminal group via cocondensation
method has been obtained. The organo-modified nanosilica consists of
amorphous powder with particle size of ~ 60 nm, highly monodispersed and low
aggregation. Structural defects in organo-modified silica nanoparticle have been studied
via optical absorption and photoluminescence in the range of vacuum ultraviolet
(VUV), UV visible, and near-IR. Raman analysis also demonstrates the surface defectrelated
optical properties. Post-modification of as-prepared silica nanoparticles (~ 10
nm in size) are converted into organo-functionalized silica with new size of 11-13 nm,
but with higher aggregation and existence of self-condensed of organosilanes. Higher
organic species content with amino functionality is observed for in-situ modified silica,
leading to more surface hydrophobicity that can improve the compatibility and
dispersion of organo-modified silica into polymeric matrix in nanocomposite
fabrication. Finally, the core-shell system of silica-polypyrrole nanocomposite with
particle size of 60-70 nm has been synthesized via oxidative dispersion polymerization
using pure silica and modified silica which was previously prepared.
Description
Keywords
Silica nanoparticles, synthesis, Modification and their applications , In the fabrication of polypyrrolebased Silica nanocomposites