Synthesis and characterisation of superhydrophobic and transparent composite films based on silica nanoparticles

Wetting state of a surface is characterized by the contact angle (CA). A surface with water contact angle greater than 90º is usually referred to as hydrophobic, and one with water CA higher than 150º is qualified as superhydrophobic. The superhydrophobic surfaces have drawn lot of interest in recent years. In this study, transparent and superhydrophobic thin films are prepared on glass surfaces. Water repellent and optical transmittance of the surfaces were investigated for different solutions. Moreover, influence of the concentrations and sizes of silica nanoparticles were studied. Contact angle on the surface was measured by using with Drop Shape Analysis System 100 (DSA100) contact angle meter. Scanning electron microscope (SEM) was used for investigating microstructure of the prepared surface. Chemical composition of surface was analyzed with Electron dispersive X-ray spectroscopy (EDX). Roughness of surfaces, which was prepared on glass, was investigated using Atomic force microscopy (AFM). Optical transparency of surfaces was measured with Ultraviole-visible spectroscopy (UV-vis). The deposition of nanoparticles and their clusters onto the substrates provide high roughness, which is essential for superhydrophobic properties. The transparent property of glass slides changes reversely with concentration of nanoparticles. Contact angle measurements of the prepared surfaces were obtained above 150º. In addition, the highest transparency for thin film was found 94%. The maximum contact angles of THS-SiO2 films is higher than that of PDMS-SiO2 films.