In Situ Tracking Photodegradation of Trace Graphene Oxide by the Online Coupling of Photoinduced Chemical Vapor Generation with a Point Discharge Optical Emission Spectrometer.

The photostability of graphene oxide (GO) strongly affects the performance of its products in optics and photonics. However, the photostability of GO, especially at trace levels, remains largely unexplored mainly because of the lack of available techniques. Herein, we developed a novel online system consisting of a highly efficient photoinduced chemical vapor generation reactor and an in situ measurement technique using a miniaturized and sensitive point discharge optical emission spectrometer. On the basis of the results of inorganic carbon species, abundant oxygen-containing functional groups on GO nanosheets made the degradation much easier than graphene. Under the optimized conditions (e.g., initial pH of 2.8 and binary photocatalysts dose of 200 mM H2O2, 1.0 mM Fe3+ ions, and 50 mg/L TiO2 NPs), the limit of detection for GO was 87.5 μg/L C with a linear range of 0.5-10 mg/L C. Specifically, the accuracy and reliability of the developed system was verified by quantifying self-prepared GO as well as aggregated GO in natural organic matter-rich water samples. Finally, the sunlight-induced photodegradation of GO under simulated environmental conditions was successfully tracked. The developed system is a promising platform for in-time quality control of GO-based products as well as predicting the occurrence, transformation, and fate of GO at environmentally relevant concentrations in the natural aquatic environment.