Dependence of binder and photocatalyst in photocatalytically active printing ink

Abstract

Photocatalytically active printing ink changes its colour when exposed to UV light. The ink is based on photocatalyst which decomposes organic dye in presence of UV light causing the changes in colour. Such process can be used as a simple UV dosimeter as its colour change depends on duration to UV light exposure. We have prepared such an ink based on redox dye 2,6-dichloroindophenol (DCIP), photocatalyst titanium dioxide (nanodimensional anatase), reducing agent (glycerol) and two different water based binders – hydroxyethylcellulose (HEC) and polyvinyl alcohol (PVA). Prepared ink was applied onto a substrate, exposed to UV light and analysed by UV/Visible spectra. When the ink was exposed to UV light, the colour of the redox dye DCIP was changing from blue to colourless that belongs to the dihydro DCIP form. The colour change depends on several factors: on the amount of TiO2 and UV exposure, as well as on the type of binder. In this work the influence of two selected binders and the amount of photocatalyst on the properties of ink was observed. The results show that the ink based on polyvinyl alcohol has a greater initial absorption and absorbs at higher wavelength. Colour changes were faster when higher amount of photocatalyst and HEC as a binder were used. Nevertheless, it has been confirmed that both binders are appropriate for preparation of UV active functional printing inks.