Photoluminescence-based real-time monitoring of graphene oxide photoreduction: Demonstrations and application to graphene oxide/titanium dioxide composites

Reduction of graphene oxide (GO) is a key process toward simple and massively scalable production of graphene. Analytic techniques such as X-Ray diffraction, X-Ray photoemission spectroscopy and Raman spectroscopy are excellent for ex-situ post-process assessment of the state of reduction of GO, but are unsuited for a real-time analysis during the process itself. In this work, we show that photoluminescence (PL) spectroscopy can be effectively used to this aim, allowing tracing the time dynamics of photoreduction processes. A proof-of-concept is shown, using a low-cost setup, by considering the case of pristine GO samples and of GO/titanium dioxide (TiO2) composites. We show that the PL analysis allows evidencing in real time the TiO2-induced photocatalytic contribution to GO photoreduction and the changes in photoreduction rates caused by the presence of oxygen and water molecules adsorbed on GO surfaces.