Characterization of methylene blue/TiO2 hybrid thin films prepared by the liquid phase deposition (LPD) method: Application for fabrication of light-activated colorimetric oxygen indicators

Methylene blue (MB)/TiO2 hybrid nanocomposite material has been successfully deposited on both bare glass and indium tin oxide (ITO) covered glass by the liquid phase deposition (LPD) technique. LPD method is applied to one-step hybrid dye/TiO2 deposition. An optimized amount of MB is added to the fluoride titania precursor aqueous solution in order to entrap this dye within the growing thin film of TiO2, yielding a MB/TiO2 nanocomposite material. Stable, well-adhered, intense blue-colored and optically transparent coatings have been obtained. The formation of the material can be explained by electrostatic interaction between negative charge density at the fluorinated surface of TiO2 and the cationic dye. MB/TiO2 nanocomposite material has been characterized by ATR-FT-IR, UV–vis spectroscopy, SEM, TEM, grazing angle XRD and cyclic voltammetry (CV). Deposited hybrid films exhibit photochemical activity: MB is photobleached upon UVA irradiation, using triethanolamine (TEOA) as mild sacrificial electron donor. Moreover, light-activated oxygen indicators with high optical transparency and delayed response can also be satisfactory fabricated by spin-coating a solution of TEOA with an encapsulating polymer (hydroxyethyl cellulose) over the MB/TiO2 hybrid films.