New light-sensitive materials based on TiO2 and merocianin polymetine dye

Abstract

The influence of the structure of a number of merocyanine dyes (D), which differ in the length of the polyethylene chain on one vinyl group, on their spectral, electrochemical and energy characteristics is established. Cyclic voltammetry determines their oxidation and reduction potentials. The values ​​of the HOMO and LUMO energy levels of the studied dyes from spectral and electrochemical data were calculated. It is shown that the obtained values ​​of the potentials of the energy levels of the dyes differ little (the energy difference ranges from 0,22–0,53 eV). The possibility of using merocyanins as sensitizers of titanium(IV) oxide and the creation of photosensitive heterostructures has been made. In order to investigate the possibility of using the merocyanin dyes under study as TiO2 sensitizers, the energy of the «semiconductor – dye – reagents» systems was considered. For this purpose, we compared the redox characteristics of merocyanine dyes with the electrophysical parameters of titanium(IV) oxide, as well as the redox characteristics of the reaction participants. It is established that in such systems the processes of photon transfer of the electron from the dye to the semiconductor are necessary for sensitization, and the regeneration of the original form of the sensitizers by the action of the reducing agent on the cation radicals formed is thermodynamically allowed. The conclusion about the possibility of using the studied merocyanines as effective sensitizers was confirmed by the results of the study of the photocatalytic activity of D/TiO2 heterostructures in the reaction of methylene blue formaldehyde recovery under different irradiation conditions and at different dye concentrations. The explanation for the found laws is offered. Scientific approaches to the production of new photosensitive systems with an expanded range of photosensitivity and a given level of photocatalytic activity have been developed.