Facile synthesis of ultra-smooth and transparent TiO2 thin films with superhydrophilicity

• A facile route has been developed to fabricate TiO2 thin films.
• The TiO2 film possessed an ultra-smooth surface.
• The film showed a high visible transparency with a transmittance higher than 87%.
• Completely wetting without UV irradiation demonstrated a superhydrophilic surface.

A facile modified dip coating method has been developed to fabricate ultra-smooth, transparent and superhydrophilic TiO2 thin films on glass substrates. Post-annealing at temperatures over 400 °C in dry air resulted in anatase TiO2 structures. The TiO2 film by coating once possessed an ultra-smooth surface with a root mean square (RMS) roughness of 2.6 ± 0.7 nm, which was attributed to the auxiliary effect of N2 flow during the formation of the film. The film on glass substrate showed a high visible transparency with a transmittance higher than 87%, which was comparable to that for a clean glass slide. Completely wetting was realized on the TiO2 film within 60 ms from water droplet deposition without UV irradiation, indicating that a superhydrophilic surface was achieved. Tests on hydrophilic stability showed the TiO2 film remained superhydrophilic with an equilibrium water contact angle less than 5° within 15 days. The TiO2 film on glass substrate also displayed excellent antifogging performance.