An ordered fish scale-like Co-TiO2/GO inverse opal photonic crystal as the multifunctional SERS substrate

Abstract Nowadays, developing highly sensitive and multifunctional surface-enhanced Raman scattering (SERS) substrates is very significant. Here, a new cobalt (Co)-doped titanium dioxide (TiO2)/graphene oxide (GO) inverse opal photonic crystal (IO PC) was successfully synthesized using polystyrene opal as the template. The scanning and transmission electron microscope images demonstrate the ordered fish scale-like shape while the element mappings display the uniform element distribution of the Co-TiO2/GO IO PC. Raman spectra show that the detection limit of 4-mercaptobenzoic acid (4-MBA) on the Co-TiO2/GO IO PC SERS substrate is as low as 10-12 M, exhibiting better SERS effect than TiO2 and Co-TiO2 IO PCs. Amperometric I-t curves reveal that the photocurrent density of Co-TiO2/GO IO PC is six and three times more than that of TiO2 and Co-TiO2 IO PCs under simulated sunlight irradiation, respectively. Furthermore, UV-Vis spectra indicate that the degradation rate of methylene blue and Congo red over Co-TiO2/GO IO PC photocatalyst could separately reach 96% and 93%, which are much higher than that over TiO2 and Co-TiO2 IO PCs. The outstanding performance of Co-TiO2/GO IO PC was caused by that the Co2+ doping and GO addition broadened the light absorption to visible range, the electron traps resulted from Co2+ doping inhibited the recombination of electron-hole pairs and doping levels promoted TiO2-to-molecule charge-transfer process, which were confirmed by the UV-Vis spectra, PL spectra and SERS spectra, respectively. At the same time the periodic IO PC structure led to multiple scattering of light and improved the light-mass interaction. The prepared Co-TiO2/GO IO PC may be a promising material in SERS effect, water purification and so on.