PLASMA-ASSISTED SYNTHESIS OF POLYMER-CAPPED DYE-SENSITIZED TiO2-BASED PHOTOCATALYSTS FOR METHYL ORANGE AND CAFFEINE PHOTODEGRADATION

Abstract

In this study, a low pressure plasma is employed for the synthesis and modification of TiO2-based photocatalysts. The commercially available TiO2 nanoparticles were impregnated with a Ruthenium-based photosensitizer (N3). The samples were subsequently exposed to a plasma to promote the formation of a plasma-polymerized poly-allyl layer. A plasma was excited by a radio frequency (RF) power source. An argon (Ar) was used as a carrier gas. Photocatalytic activity of samples was investigated in the photodegradation of methyl orange (MO) and caffeine in aqueous solution under UV irradiation. Comparison of catalysts activity was performed between N3-containing TiO2 covered with a polymer layer, TiO2 covered with a polymer layer, Ar-RF plasma treated and untreated TiO2. The rate constant of photodegradation was used to express the catalytic reactivity of the catalyst. The maximal value of rate constant of MO degradation reaction was found to be 1.1∙10-2 s-1 for TiO2 covered with a poly-allyl layer. The value of rate constant was 4.4 times higher for TiO2 covered with polymer layer than that for untreated TiO2. However, for caffeine photodegradation reaction, no increase in catalytic activity was observed for modified TiO2. The difference in catalytic performance in the photodegradation of MO and caffeine may be caused by differences in reaction mechanism. Enhancement of photocatalytic activity towards MO photodegradation by coating of TiO2 with poly-allyl layers might be due to the photogenerated electron transfer from polymer to TiO2. The catalysts were characterized by the time resolved photoluminescence (TR-PL) and infrared (IR) spectroscopy.