Organic Fluorescent Labeling and Sorting for Plastic Recycling

Plastic pollution poses critical global challenges, driving urgent needs to transition from linear models to circular plastic economies. A significant challenge in plastic recycling lies in the reduced economic value of recycled plastics, primarily caused by polymer contamination. Even polymers of the same type but differing grades are often mixed during sorting processes, leading to compromised material performance. To address this, we develop a fluorescence labeling system enabling high-resolution plastic sorting. A series of fluorescent molecules was employed to label polymers via both physical blending and chemical post-polymerization modification methods. Each fluorescent molecule serves to label individual polymers, and combinations of multiple fluorescent molecules allow for cross-labeling of different polymers. Physical blending offers a high-volume, cost-effective, and easily industrialized approach, while chemical modification improves fluorescence stability and reduces leaching susceptibility. Notably, these strategies do not alter the thermodynamic and mechanical properties of the polymers. The labeling system enables precise polymer identification through a two-step characterization protocol. Firstly, polymer types are classified via Fourier transform infrared (FT-IR) spectroscopy, and then specific grades are determined via fluorescence spectroscopy analysis. This method enables precise recycling and more efficient utilization of plastics, ultimately improving resource efficiency and the economic viability of circular plastic systems.