Organization of SiO₂ and TiO₂ Nanoparticles into Fractal Patterns on Glass Surface for the Generation of Superhydrophilicity

Abstract

The superhydrophilic surfaces have many important practical applications such as antifogging, antifouling, self-cleaning, etc. The present study demonstrates a simple and facile template-assisted dip-coating approach for the organization of silica (SiO2) and titania (TiO2) nanoparticles (NPs) into fractal patterns on the glass surface. The pure NPs suspension showed a “coffee ring effect” and did not form any organized pattern on the glass surface after drying. In this reported method, NPs were organized into fractal patterns using a template consisting of sodium carboxymethyl cellulose (CMCNa) and oxalic acid mixture in the presence of a cationic surfactant (CTAB). The presence of surfactant plays a major role to alter the coffee ring effect because of a Marangoni flow in the direction of droplet edge to its center induced by the surface tension gradient and surface potential of the particles, which eventually helps to get a uniform fractal pattern. Finally, the fractal patterns of only SiO2 and TiO2 NPs were attained on the glass surface after calcining the CMCNa template at 450 °C. The obtained fractal patterns of SiO2 and TiO2 coated glass surfaces showed the average water contact angle of ∼6° and ∼8° respectively, whereas coating of only NPs without pattern could not achieved such low average contact angle. These coated surfaces were found to have an excellent antifogging property (transparency of the surface) in the presence of water vapor.

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