Synthesis and Characterization of Size-Controlled Titania Nanorods through Double Surfactants

A synthetic technique based on a two-step sol-gel hydrothermal method using cetyltrimethylammonium bromide (CTAB) and triblock copolymer PEO₁₀₆-PPO₇₀-PEO₁₀₆ (F127) as double surfactants with the assistance of three amines (ethylamine (EA), diethylamine (DEA), and triethylamine (TEA)) for fabrications of anatase titania nanorods is proposed. The formation and growth mechanisms of TiO₂ crystals are described. We discovered that crystal size reduces with an increase in the number of alkyl substituents on the nitrogen of amines because the steric hindrance of the bulky alkyl substituent around nitrogen suppresses the nucleation and crystal growth rate. The size of titania from 80 to 220 nm is modulated with concentrations of EA, DEA, and TEA. The amines are considered as catalysts for morphological evolution of TiO₂ crystals. The results indicate that the incorporation of double surfactants (F127-CTAB) has a dual role, acting as a chelating agent for titania against external forces and a capping agent inhibiting the three-dimensional growth of TiO₂ crystals.