Photocatalytic degradation of rhodamine 6G on Ag modified TiO2 nanotubes: Surface-enhanced Raman scattering study on catalytic kinetics and substrate recyclability

Abstract

Abstract A method for the investigation of photocatalytic degradation of organic molecules adsorbed on the surface of a compound nanostructure, silver nanoparticle (Ag NP) modified titania nanotubes (TiO 2 NTs), namely Ag/TiO 2 NTs, was proposed. The method was applied to the photocatalytic degradation of rhodamine 6G (R6G) dye molecules in order to determine its effectiveness. The surface-enhanced Raman scattering (SERS) technique was employed to monitor the photodegradation processes on these bifunctional nanostructures. The photocatalytic characteristic was attributed to the TiO 2 NTs; however, the SERS activity was caused by the Ag NPs. The Ag/TiO 2 NTs were able to detect R6G molecular probes with concentration down to 10 −8 M. The substrates could not only degrade the adsorbates, but also discard them off under ultraviolet irradiation owing to the high photocatalytic activity of TiO 2 . Thus, the substrates were able to self-clean and be reused for a new SERS detection cycle. The photodegradation and SERS results revealed that Ag/TiO 2 NTs acted as promising candidates for photocatalytic activity and SERS substrates; and exhibited high recyclability in the detection of organic molecules. The optimized SERS-active substrates were then employed to study the photodegradation of R6G. The photodegradation kinetics analysis was assessed by selecting the strongest SERS peaks which indicated that the kinetics of the photodegradation of R6G followed the pseudo-first order reaction. Finally, the results presented herein demonstrated that the fabricated Ag/TiO 2 NTs nanostructures were remarkably suitable as photocatalytically active SERS substrates. Further, the substrates could be effectively utilized for highly sensitive in situ monitoring of the surface photodegradation processes of organic molecules and could be recycled in a more environmentally sustainable manner.