In continuing attempts to reduce the size of nanosilica by researchers, a homogeneous, highly dispersed, and stable
silica nanoparticle of ∼7.1 nm in the primary size range was reported by Rahman et al. [23] at the optimum
conditions of sol-gel process, under the influence of low frequency ultrasound. The optimized technique developed is
simple and reproducible, affording a high yield of ∼75% of nanometer silica in a primary size range.