Advanced photocatalysis mediated by TiO2/Ag/TiO2 nanoparticles modified cotton fabric

Novel cotton-based TiO2/Ag/TiO2 nanocomposites for wastewater treatment were developed by fine chemical synthesis path with the goal of coping with wastewater issues and environmental remediation. The photocatalytic performances of nanocomposites were tested during photodegradation processes of RB, AO7 and MR under simulated solar light. Double- and single-loaded nanocomposites were synthesized by a simple bottom-up approach implying in situ photoreduction of Ag+ ions on the surface of TiO2 NPs previously deposited on cotton fibers from colloids. The spherical-like colloidal TiO2 NPs (4.5 nm) and TiO2/Ag NPs (8 nm) and the formation of uniform TiO2/Ag and TiO2/Ag/TiO2 nano-coatings on cotton fibers were examined by TEM and FESEM. The reduction of Ag+ ions on TiO2 surface was undoubtedly proven by the appearance of SPR band of Ag NPs in UV/Vis spectra. Raman spectroscopy clearly confirmed the presence of anatase TiO2 in nanocomposites. Quantitative determination of TiO2 and Ag in nanocomposites was accomplished using EDX and ICP-OES. The cotton-based TiO2/Ag/TiO2 nanocomposite showed the highest photocatalytic efficiency (> 90%) and maintained its removal efficiency after three reuse cycles, indicated its exceptional photochemical ability. The initial idea of improved photocatalytic performances of a TiO2 NPs double-layer with immobilized Ag NPs was justified as the TiO2/Ag/TiO2 processed sample contributed additional binding sites for dye molecules. Considering that the photocatalytic activity of the cotton-based TiO2 and TiO2/Ag samples was practically imperceptible, it can be assumed that the synthesized Ag NPs act predominantly as electron traps in the double-loaded synthesized system.