Molecular fingerprints of natural organic matter dictate eco-corona assembly and stability of black phosphorus nanosheets in aquatic environments.

Abstract

Black phosphorus nanosheets (BPNS) show promising results in various environmental applications, yet their fate after release into natural waters is poorly investigated. A critical knowledge gap remains in how the molecular heterogeneity of natural organic matter (NOM) from different sources influences eco-corona formation on BPNS and subsequent colloidal behavior. We systematically investigate this linkage using adsorption kinetics, FT-ICR MS-based molecular fingerprinting, and DFT-assisted charge density difference analysis across five NOM samples (a fulvic acid standard and four environmental isolates). Eco-corona formation on BPNS followed pseudo-second-order kinetics (R2 =0.995- 0.998), with protein-like components enhancing initial uptake rates, while lignin-like compounds (56∼67% of assigned formulas) determined the ultimate adsorption capacity. Moreover, FT-ICR MS revealed an increased relative abundance of signals above m/z 700 in the washed corona extracts compared with the initial NOM samples. In contrast, the relative proportions of carbohydrate-like and lipid-like formulas generally decreased, indicating selective molecular fractionation during eco-corona formation. DFT calculations identified methoxy (-OCH3, -1.359 eV) groups in lignin and carboxyl (-COOH, -1.462 eV) groups in tannin as favorable interaction sites within the examined molecular models, with flat-lying configurations and interfacial charge redistribution visualized by charge density difference (CDD) analysis. Notably, NOM treatments influenced BPNS aggregation and sedimentation behavior, as evidenced by differences in apparent hydrodynamic diameter growth, C/C0 ratios, and zeta potential over 48 h, suggesting that NOM composition plays an important role in regulating BPNS colloidal stability. These findings establish mechanistic insights linking NOM source composition to adsorption behavior and BPNS stability, highlighting potential implications for the transport and ecological risks of two-dimensional nanomaterials in natural aquatic systems.

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