Generation of photo charge in poly(ethyleneimine)-TiO2-anthocyanin modified papers conditioned at different humidities

The article describes the influence of humidity on the surface photodielectric properties of papers prepared from poly(ethyleneimine)-TiO2 nanoparticles-anthocyanin modified cellulose fibres. The anthocyanins were extracted from purple cabbage, beet-root, plum peel, red wine and red currant juice. The samples were conditioned to various relative humidities (from 9 to 100%) and illuminated with white visible light, λ ≥ 405 nm. The poly(ethyleneimine)-TiO2-anthocyanin modified samples showed similar photodielectric behaviour that can be clearly distinguished from the samples modified solely with poly(ethyleneimine)-TiO2. Generally, an increase in humidity enhances the conductivity of the samples and induces an increase in the amount of photo-induced charge. Also, at higher humidities (above 80%), the samples with anthocyanin showed significantly higher values of photo-induced charges with respect to anthocyanin free samples. The presented results suggest that the presence of water molecules promotes electron-injection processes from the anthocyanin to the semiconductor surface.