Photochemical Transformation of Graphene Oxide in Sunlight Wen-Che Hou Indranil Chowdhury David G. Goodwin W. Matthew Henderson D. Howard Fairbrother Dermont Bouchard Richard G. Zepp 10.1021/es5047155.s001 https://acs.figshare.com/articles/journal_contribution/Photochemical_Transformation_of_Graphene_Oxide_in_Sunlight/2185726 Graphene oxide (GO) is promising in scalable production and has useful properties that include semiconducting behavior, catalytic reactivity, and aqueous dispersibility. In this study, we investigated the photochemical fate of GO under environmentally relevant sunlight conditions. The results indicate that GO readily photoreacts under simulated sunlight with the potential involvement of electron–hole pair creation. GO was shown to photodisproportionate to CO<sub>2</sub>, reduced materials similar to reduced GO (rGO) that are fragmented compared to the starting material, and low molecular-weight (LMW) species. Kinetic studies show that the rate of the initially rapid photoreaction of GO is insensitive to the dissolved oxygen content. In contrast, at longer time points (>10 h), the presence of dissolved oxygen led to a greater production of CO<sub>2</sub> than the same GO material under N<sub>2</sub>-saturated conditions. Regardless, the rGO species themselves persist after extended irradiation equivalent to 2 months in natural sunlight, even in the presence of dissolved oxygen. Overall, our findings indicate that GO phototransforms rapidly under sunlight exposure, resulting in chemically reduced and persistent photoproducts that are likely to exhibit transport and toxic properties unique from parent GO. 2015-03-17 00:00:00 sunlight conditions Photochemical Transformation presence 2 months rGO species irradiation equivalent oxygen content scalable production Kinetic studies show material CO 2 SunlightGraphene oxide LMW Graphene Oxide exhibit transport sunlight exposure semiconducting behavior