Interfacial interactions of submicron plastics with carbon dots: Insights into the interface properties of microplastic weathering.

The interfacial properties and environmental behavior of microplastics (MPs) will change with weathering. A new idea to study the interfacial properties of MPs is provided based on fluorescence response and light scattering changes. Submicron microspheres (PS-AA) obtained by soap-free emulsion polymerization have a well-defined composition and clean surface with carboxyl groups. The interfacial properties of PS-AA changed after Fenton and UV aging, and the sharp edges became blurred. Information on the interfacial interactions of leaf-derived carbon dots (R-CDs) and citrate carbon dots (B-CDs) with aged PS-AA was obtained by recording fluorescence and scattering changes. R-CDs can fluorescently respond to carrying contaminants on aged PS-AA, and their correlation increases with the degree of aging (R2=0.8388). The scattering peak of PS-AA decreased after aging, and the change in scattering/fluorescence ratios with concentration had a good linear relationship under the coexistence of B-CDs (R2=0.9983). Aging of PS-AA increases the contamination-carrying capacity and decreases the optical properties, which may be attributed to the increased oxygen-containing functional groups, ring opening of substituted benzene, and shell decomposition. The response mechanism of carbon dots (CDs), the aging process of PS-AA, and the interfacial behavior were further explained based on the density functional theory (DFT). This study reveals the changes in interfacial properties of submicron plastics with the aging process based on fluorescence response and scattering changes.