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Assessing photoreductive performance of TiO2 nanocomposites sensitized with zwitterionic and quaternernized Zn-phthalocyanines

2020    Kesir, M. Koc; Dilber, G.; Sokmen, M.; Durmus, M.

Phthalocyanines (Pcs) can be considered as alternative synthetic inorganic sensitizers to expand the active spectral range. If the TiO2 conduction band (CB) lies in the similar energy level of the LUMO orbital energy of the Pc ring a charge transfer occurs. Additionally, these Pc sensitized TiO2 catalysts can be used as energy harvesting nanocatalyst in dye sensitized solar cells (DSS). Therefore, their electron capture capacity reflects the possibility of their future applications. In this study, novel ZnPc/TiO2 nanocomposites were produced using zwitterionic (T3ZnZW, and T4ZnZW) and quaternernized (T3ZnQ, T4ZnQ) zinc phthalocyanine as sensitizer (1% w/w mass fraction of TiO2) by sol-gel procedure. Total four derivatives, nonperipheral and peripheral positioned zinc phthalocyanins, were used for the sensitization of TiO2. These structures were specifically designed to shift the light absorption to longer wavelength, increase the light absorption and harvesting capacity as well as facilitate the electron transfer. Neat TiO2 nanoparticles were also prepared and compared with ZnPc sensitized ones. After characterization of the composite catalysts their photoreductive capacity was measured for photocatalytic reduction of Cr(VI) (10 mg/L) at 1 g/L catalyst mass in the presence and absence of light (6 W lamp emitting 365 nm light). Sol-gel process produced more effective catalysts and presence of ZnPc as sensitizer definitely added value to the catalyst under studied conditions. Neat TiO2 reduced 66% of Cr(VI) ions and all dye sensitized TiO2 catalysts were more effective than neat TiO2 except for T3Znp/TiO2. Especially zwitterionic derivatives T3ZnZW and T4ZnZW sensitization extremely effective for faster electron transfer. (C) 2020 Elsevier B.V. All rights reserved.