As we explained in previous research [28], the use of ammonia in hydrothermal reaction can make the hydroxyl groups replace the acetic acid groups on TiO2 nanoparticle surface, and the hydroxyl group caped nanoparticles can combined together to form bigger nanoparticles. By using the Sercherr equation, the average sizes of crystallites in TiO2 spheres are 8 nm (without using ammonia) and 15 nm (using ammonia).