Self-cleaning of SiO-TiO coating: Effect of sonochemical synthetic parameters on the morphological, mechanical, and photocatalytic properties of the films.

Among the different properties of the hydrophobic semiconductor surfaces, self-cleaning promoted by solar illumination is probably one of the most attractive from the technological point of view. The use of sonochemistry for nanomaterials' synthesis has been recently employed for the associated shorter reaction times and efficient route for control over crystal growth and the management of the resulting material's photocatalytic properties. Moreover, the sol-gel method coupled to sonochemistry modifies the chemical environment, with reactive species such as •OH and HO, which yield a homogeneous synthesis. Therefore, in the following investigation, the sol-gel method was coupled to sonochemistry to synthesize a SiO@TiO composite, for which the sonochemical amplitude of irradiation was varied to determine its effect on the morphology and mechanical and self-cleaning properties. SEM and AFM characterized the samples of SiO@TiO composite, and while the micrographs indicate that a high ultrasonic energy results in an amorphous SiO@TiO composite with a low rugosity, which was affected in the determination of the contact angle on the surface. On the other hand, FTIR analysis suggests a significant change in both SiO-SiO and SiO-TiO chemical bonds with changes in vibrations and frequency, corroborating an important influence of the sonochemical energy contribution to the hydrolysis process. Raman spectroscopy confirms the presence of an amorphous phase of silicon dioxide; however, the vibrations of TiO were not visible. The evaluation of hydrophobic and self-cleaning properties shows a maximum of ultrasonic energy needed to improve the contact angle and rhodamine B (RhB) removal.