Fluorescence evolution processes of visible/ultraviolet photo-reduced graphene oxide

The ongoing revolution in optoelectronics based on graphene and graphene oxide (GO) demands the comprehension of reduction mechanisms. One of the most feasible reduction methods for GO is photo-reduction, which has been widely used and investigated. Here, from the perspective on the fluorescence evolution process of photo-reduced GO, we have studied the mechanisms of visible/ultraviolet (UV) photo-reduced GO in detail by steady-state photoluminescence spectroscopy and femtosecond transient absorption spectroscopy. It demonstrates that the oxygen-containing functional groups (OFGs) in sp3 domains of GO are initially reduced by visible light, while the OFGs in the boundary between neighboring sp2- and sp3-hybridized domains of GO prefer to be reduced by UV light. Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy further prove the partial elimination of OFGs and the reconstruction of the C = C bonds, despite the GO reduced by visible light or UV light. Our work provides insight into the mechanisms of visible/UV photo-reduced GO.