Synthesis of mono-dispersed spherical silica particles containing covalently bonded chromophores

Abstract

Organic–inorganic ultraviolet (UV) active hybrid
materials have been prepared by a sol-gel process
from benzophenone derivatives and tetraethylorthosilicate.
The silica particles are spherical in
shape and have a narrow size distribution which
remains unchanged up to organic chromophore
concentrations of 0.2 mmol g)1. At higher concentrations
the spheres become less regular and
fuse. A dependence of the material absorption
properties on the particle size (at the same organic
chromophore concentration) and on the concentration
of surface grafted chromophores was noted.
The most effective UV filter materials were found
in a combination of silica incorporated chromophores
and surface grafted chromophores at an overall
low chromophore concentration. A comparison
of the photostability of chromophores at standardized
UV irradiation revealed an increase in stability
for silica incorporated and surface immobilized
benzophenone compared to benzophenone in a
homogeneous solution.