Uniform sized silica nanoparticles for the coating were further
purified by centrifugation. Typically, the obtained silica nanoparticles
solution was centrifuged at 3000 rpm to remove some small
sized silica nanoparticles. The centrifuged pellets were dispersed
into ethanol with a volume ratio of 1:10 and this solution was used
as parent solution for the following experiments.
In our experiments, the original solution was diluted 1:500 (v/v)
(see Sections 2.3 and 3.1, the above 10 dilution was followed by a
50 dilution) for nanoparticle coating on PMMA surface