ZnO/TiO2 Nanocomposite Synthesized by Sol Gel from Highly Soluble Single Source Molecular Precursor

Abstract

Single source molecular precursors (SSPs) provide an opportunity to get control over the microstructure of nanomaterials at atomic level. A SSP was designed and developed for the synthesis of ZnO/TiO2 nanocomposite by sol gel method. In a typical synthesis process, a bimetallic molecular compound with chemical formula [Cl2TiZn(dmae)4] (dmae=dimethylaminoethanol) was synthesized and its chemical composition was determined by elemental analysis. The obtained compound has shown excellent solubility in common organic solvents, a prerequisite for its use in sol gel method as SSP. The SSP obtained was controllably hydrolyzed by adding equimolar amount of water using ethanol as solvent to get ZnO/TiO2 nanocomposite gel. The resulting gel was precipitated at pH=9 and sintered at 200 °C (T200), 400 °C (T400), and 600 °C (T600). The XRD analyses have shown that the as synthesized (non-sintered, T00) powder was amorphous. However, the crystallinity improved upon sintering, and the XRD analyses revealed that the resulting nanomaterials were composed of mixed oxides i.e., ZnO and TiO2. The ZnO was in wurtzite (hexagonal) while the TiO2 was in brookite (orthorhombic) phase. The increase in particle size was further confirmed from BET analysis and SEM micrographs. The IR spectra obtained for the resulting powder have shown the peculiar vibrational bands for Zn-O and Ti-O. Furthermore, the IR spectra revealed that the non-sintered ZnO/TiO2 nanocomposite had significant number of OH group which was removed upon sintering. The photocatalytic activities of the ZnO/TiO2 nanocomposites were tested. All the samples have shown good photocatalytic activities. However, the T400 has shown higher activity than the T00, T200, and T600. The higher photocatalytic activity of T400 than T00, T200, and T600 may be due to improved crystallinity which ensures efficient grain boundary interfaces.