Formation of Silica Nanoparticles by Hydrolysis of TEOS Using a Mixed Semi-Batch/Batch Method

Abstract

A new method for preparing silica nanoparticles, which consists of a two-stage semi-batch/batch hydrolysis reaction of tetraethylorthosilicate (TEOS), is presented. A relatively slow rate of hydrolysis of the TEOS occurred during the semi-batch process, which resulted in larger silica particles with a narrower size distribution. This was in direct contrast to the batch process. An example of reduction in particle size for an initial semi-batch and subsequent batch reaction is shown. On completion of the initial semi-batch step, the silica particles had a diameter of 106 nm. As the subsequent batch reaction proceeded, the mean size of the particles decreased to 23 nm. In this work, it was found that the optimal conditions for the silica nanoparticles using this mixed method were as follows; (TEOS: 0.5 M, H₂O: 6.0 M, NH₄OH: 0.2 M, feed rate: 5.0 ml/min, temperature: 42.5°C). In conclusion, a mixedsemi-batch/batch system suggested a new probability for the synthesis of nanoparticles.