title: Photochemical transformation of graphene oxide in sunlight.
abstract: 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 CO2, 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 CO2 than the same GO material under N2-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.
authors: †National Research Council Associate, National Exposure Research Laboratory, Ecosystems Research Division, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States.|‡Department of Environmental Engineering, National Cheng Kung University, Tainan City 70101, Taiwan.
authors: Wen-Che
authors: WC
authors: Hou
authors: †National Research Council Associate, National Exposure Research Laboratory, Ecosystems Research Division, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States.
authors: Indranil
authors: I
authors: Chowdhury
authors: §Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.
authors: David G
authors: DG
authors: Goodwin
authors: ⊥National Exposure Research Laboratory, Ecosystems Research Division, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States.
authors: W Matthew
authors: WM
authors: Henderson
authors: §Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.
authors: D Howard
authors: DH
authors: Fairbrother
authors: ⊥National Exposure Research Laboratory, Ecosystems Research Division, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States.
authors: Dermont
authors: D
authors: Bouchard
authors: ⊥National Exposure Research Laboratory, Ecosystems Research Division, U.S. Environmental Protection Agency, Athens, Georgia 30605, United States.
authors: Richard G
authors: RG
authors: Zepp
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D007700:Kinetics; D010087:Oxides / Q000737:chemistry*; D010777:Photochemistry; D013472:Sunlight; D014867:Water / Q000737:chemistry
chemical_list: D010087:Oxides; D014867:Water; D002245:Carbon Dioxide; D006108:Graphite