. The drawback of this technique is that, if the amount
of TEOS exceeds a critical value, a second population of
particles will appear. Using this technique, it is possible to
prepare more monodisperse particles and increase their mass
fraction in the sol, but with this method, it is not possible to
increase the size of the monodisperse particles beyond 1 µm.
The effect of electrolyte on size of silica nanoparticles was
described by Bogush and Zukoski [5], and in their study,
they reported that when the electrolyte (NaCl) concentration
was increased from 0 to 10−4 M, the particle size increased
from 340 to 710 nm.
Huang and co-workers have reported that sonication
during a reaction could significantly increase the yield of
carbodiimide-mediated amidations [13]. In view of this, in
the present study, we have determined the effect of each
reagent on particle size in addition to the effect of temperature
on ultrasonication. To our knowledge, this is the first
report on a sequential addition method for preparation of
silica particles by a sol–gel process.