Synthesis of TiO2 nanoparticles by hydrolysis of TEOT and decrease of particle size using a two-stage mixed method

A new preparation method of particles was introduced, which consisted of a semibatch–batch two-stage reaction to decrease the size of TiO2 fine particles. Using a semibatch process as a first stage, the particle size grew to a certain level (132 nm). Using a batch process as a second stage, however, the particle size decreased about 42 nm. The particles prepared by using a two-stage (semibatch–batch) method had a smaller mean particle size and smaller standard deviation than those obtained from the single-stage process. In this work, the statistical experimental method was also used to compare the various properties of the TiO2 particles according to the six parameters [concentration of TEOT during 1st and 2nd stages, reaction temperature during 1st and 2nd stages, the amount of hydroxypropyl cellulose (HPC) during 1st and 2nd stages]. It was found that the optimum conditions for the maximum reduction of TiO2 particle size using this method were as follows: (1st TEOT (M): 0.091, 2nd TEOT (M): 0.146, 1st temperature (°C): 20.0, 2nd temperature (°C): 38.2, 1st HPC (×10−2 g/cm3): 0.018, 2nd HPC (×10−2 g/cm3): 0.290). The experimental results measured by using the above optimum conditions were in agreement with calculated results and produced the smallest size (∼42 nm in diameter) with the value of DPS (−90 nm). In addition, we found that the main parameters affecting the decrease of particle size were concentration of TEOT and the reaction temperature during second stage.