Physical-chemical characterization of titanium dioxide layers sensitized with the natural dyes carmine and morin

The titanium dioxide (TiO2)-based layers sensitized with carmine and morin dyes were prepared using commercial P25 TiO2 powder as starting material. The influence of natural colorants as natural photosensitizers on TiO2 photoactivity was discussed from the point of view of UV-VIS and Fourier transform infra-red (FTIR) spectroscopy, fluorescence analysis, microscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms determination. A shift to visible region of the sensitized TiO2 layers is observed. The decrease of sensitized TiO2 band gap improves its photoactivity in the visible domain. The fluorescence quenching of TiO2 sensitized with carmine is correlated with better adsorption of the dye molecules to the TiO2 surface and with electron injection process, also. The FTIR absorption spectra of samples proved the presence of dye molecules on TiO2 nanoparticles surface. Thus, the investigated sensitized TiO2-based layers could have potential in photoelectrochemical applications.