Variable structural colors and hydrophobicity of SiO2/polyethyleneimine coating on glass substrate

Films composed of nanoparticles have been commonly used in decorative applications due to their striking colors and useful self-cleaning properties. An efficient option for the structural coloration has been developed through fabrication of the thin films on substrates from SiO2 nanoparticles and PEI. The surface morphology and microstructure of SiO2/polyethyleneimine (PEI) film on glass substrate were analyzed with an SEM, AFM, and thickness analyzer. The homogeneous coatings of limited SiO2 aggregation with air voids were formed on glass substrates. It was strongly suggested that optical properties of the films came from the single-layer thin film interference effect. The structural colors of SiO2/PEI films were captured by digital camera, integrating sphere spectrophotometer and multi-angle spectrophotometer. The results indicated that the films illuminated distinctly as the thickness increased, and presented different lightness values and hues at various viewing angles. Moreover, those films with some surface roughness exhibited high water static contact angle, which endowed the films potential hydrophilicity and self-cleaning property.