Highly transparent superhydrophobic thin film with low refractive index prepared by one-step coating of modified silica nanoparticles

An easy and effective method to prepare superhydrophobic thin film has been developed. The film with optically transparent and low refractive index was composed by one-step coating with modified silica nanoparticles. The silica nanoparticles were prepared by sol–gel process of hydrolysis and condensation of alkoxysilane compounds and then surface modification silica nanoparticles, 50 ± 10 nm, were accomplished using methoxytrimethylsilane (MOTMS). Water contact angle of film increased with the weight of MOTMS of silica sol. When the weight of MOTMS was optimized, the water contact angle and sliding angle of film were 152.8° and less than 10°, respectively. The transmittance of film was also increased as compared to the un-coated microscope glass slide, from 91 to 93.5 %. The refractive index of the film was approximately 1.09 as measured by ellipsometer. The superhydrphobic thin film was also successfully made by using spray coating and the water contact angle of this film was more than 160°. Surface morphology of difference coating methods, dip and spray, were studied. Our result suggests that the film can be applied for superhydrophobicity and optical applications.