Low temperature preparation of TiO2 nanodot film on substrates

Herein, we report a photoinduced transition of hydrophobicity to high hydrophilicity of TiO2 nanodot films in applications of cell sheet engineering. A phase-separation-induced self-assembly process was adopted to prepare a TiO2 nanodot gel film on a substrate. Subsequently, a hydrothermal treatment (with ethanol/water at 140 °C for 2 h) was used to convert the nanodot gel film to TiO2 nanodot solid film. The resulting TiO2 dots were amorphous with adjustable size and density. The amorphous TiO2 nanodot film showed a conversion from a good hydrophobic surface, with a water contact angle (WCA) of 67.6 ± 2.0°, to a highly hydrophilic one, with a WCA of 5.3 ± 2.0° (i.e. almost superhydrophilic) after UV irradiation. A good reversibility was also observed.