Hydrothermal processing of nanocrystalline anatase films from tetraethylammonium hydroxide peptized titania sols

Nanocrystalline anatase films were obtained by hydrothermally treating dip-coated TiO2 gel films onto silicon substrates from tetraethylammonium hydroxide (TENOH) peptized titania aqueous sols diluted with different solvents (isoproponol, acetone and propanediol) at 240°C for 2 h. SEM, AFM and XRD analysis were used to characterize the microstructure and phase evolution of the films. The highest degree of homogeneity and good wettability towards the substrate could only be obtained with mixed solvents of acetone and isopropanol, yielding denser structure with homogeneously distributed fine grains among all the three solvents. A uniform distribution of fine grains of around 50 nm was obtained after hydrothermal treatment, while the film calcined at 500°C/2 h displayed larger grains of around 80 nm and were not so uniformly developed. All these results suggest that (a) TENOH peptized titania sol is a promising novel stock precursor for synthesizing TiO2 films; (b) hydrothermal technique is quite efficient in preparing titania nanocrystalline films compared with calcination method.