Long-Term Exposure of Graphene Oxide Suspension to Air Leading to Spontaneous Radical-Driven Degradation

Understanding the environmental transformation and fate of graphene oxide (GO) is critical to estimate its engineering applications and ecological risks. While there have been numerous investigations on the physicochemical stability of GO in prolonged air-exposed solution, the potential generation of reactive radicals and their impact on the structure of GO remain unexplored. In this study, using liquid-PeakForce-mode atomic force microscopy and quadrupole time-of-flight mass spectroscopy, we report that prolonged exposure of GO to the solution leads to the generation of nanopores in the 2D network and may even cause the disintegration of its bulk structure into fragment molecules. These fragments can assemble themselves into films with the same height as the GO at the interface. Further mediated electrochemical analysis supports that the electron-donating active components of GO facilitate the conversion of O-2 to (center dot)O(2)radicals on the GO surface, which are subsequently converted to H2O2, ultimately leading to the formation of (OH)-O-center dot. We experimentally confirmed that attacks from (OH)-O-center dot radicals can break down the C-C bond network of GO, resulting in the degradation of GO into small fragment molecules. Our findings suggest that GO can exhibit chemical instability when released into aqueous solutions for prolonged periods of time, undergoing transformation into fragment molecules through self-generated (OH)-O-center dot radicals. This finding not only sheds light on the distinctive fate of GO- GO-based nanomaterials but also offers a guideline for their engineering applications as advanced materials.nanomaterials

Automated summary

Through the use of liquid atomic force microscopy and mass spectrometry, this study reveals that prolonged exposure of graphene oxide (GO) to a solution can lead to the formation of nanopores and the disintegration of its bulk structure into fragment molecules. The active components in GO facilitate the generation of reactive radicals, which can attack and degrade the GO. This finding offers guidance for the engineering applications of GO and GO-based nanomaterials.