Photochemical Aging of Carbon-Based Materials in Water: A Review of Structural Analysis, Mechanisms, and Theoretical Advances

Carbon-based materials, including anthropogenic carbon quantum dots (CQDs), carbon nanotubes (CNTs), graphene (GR) and its derivatives (GO), as well as natural soot and biochar, have garnered significant attention due to their unique multi-scale structural characteristics and broad application prospects. This review systematically summarizes the differences in micro-morphology, crystal structure, surface functional groups, and heterogeneous composition of various carbon-based materials. On this basis, it explores how intrinsic material properties (such as carbon atom hybridization, surface defects, functional group types, and metal impurity content) synergistically regulate the rate and pathway of their photochemical aging. Furthermore, the article delves into the unified aging mechanism of “photoexcitation - charge carrier separation - interfacial reaction” for different carbon-based materials in the aqueous phase, along with the regulatory factors governing the switching of dominant pathways. Additionally, the current advances in advanced characterization techniques (e.g., in-situ spectroscopy, high-resolution mass spectrometry) and theoretical calculations (DFT/AIMD) for resolving the pristine structures and aging intermediates of carbon-based materials are summarized, providing a key theoretical foundation for a comprehensive understanding of the long-term fate and ecological risks of such materials in aquatic environments.