Effect of heat and UV-irradiation on chitosan film doped with BODIPY dyes

Abstract

The chitosan (CS) films modified by two photosensitive BODIPY compounds, differing in the presence of iodine atoms in the 2,6 position in the compound core, have been prepared and studied for thermal stability in an inert atmosphere as well as for photochemical resistance in air using highly energetic UV radiation. Characterization of UV exposed samples has been done by UV–Vis and FTIR spectroscopy and contact angle measurement, while the heat effect has been tested by thermogravimetric analysis. The photochemical stability of BODIPY dyes in solid CS matrix has been found to be relatively good. CS containing compound with iodine atoms in structure exhibits a little worse photostability than their counterparts without this element. The contact angle measurements indicate that the effect of UV radiation on surface properties is somewhat different than occurred in the sample bulk: BODIPYs efficiently hamper the surface photooxidation of CS. No effect of BODIPY on chitosan thermal stability was noted, while dyes decompose earlier, i.e., at lower temperatures in the presence of CS than heated alone. The mechanism of reactions caused by heat and UV radiation has been discussed. The protective effect of CS on BODIPY was found, which allows the prediction of a wide application of such systems in many industrial sectors, e.g., for the production of fluorescent labels and photo sensors.