Controllable synthesis of SiO2 nanoparticles: effects of ammonia and tetraethyl orthosilicate concentration

SiO2 nanoparticles can be used as drug carriers in drug delivery systems, wherein the size of the nanoparticles plays a vital role in their distribution in vivo. SiO2 nanoparticles were synthesised using the Stober method and characterised by dynamic light scattering and scanning electron microscopy. The effects of the ammonia concentration, tetraethyl orthosilicate (TEOS) concentration, water loading and alcohol type on the size and dispersion of the SiO2 nanoparticles were investigated. The results showed that the concentration of ammonia was the most important factor in dictating the size of the SiO2 nanoparticles. The size of the particles increased with increasing ammonia and TEOS concentrations. Increasing the water loading caused a reduction in the particle size but an increase in the dispersion. Both the particle size and dispersion increased with increasing alcohol carbon number. Linear relationships were observed between the SiO2 particle size and the concentrations of ammonia and TEOS, which could be used to control the size of SiO2 nanoparticles during synthesis.