Boron-doped carbon nanoparticles for identification and tracing of microplastics in "Turn-on" fluorescence mode

Microplastics (MPs) pollution is considered as one of the most serious threatens to environment and human health. How to identify and trace MPs rapidly is still a challenge. Here, we proposed a simple method to prepare boron-doped carbon nanoparticles (BCNPs) through solvothermal reaction between nitrated pyrene and boric acid for identifying and tracing MPs. These BCNPs exhibited a hydrophobic affinity to plastics and endow plastics with fluorescence emission. Interestingly, we can distinguish polypropylene (PP, strong yellow emission); polyethylene (PE, weak yellow emission); polyvinyl chloride (PVC, strong magenta emission); and polystyrene (PS, weak pink emission) according to fluorescence emission color and intensity upon 365 nm excitation, using these BCNPs via simple adsorption process. Discrepant color emissions were observed in different types of MPs due to plastics medium influence on the surrounding environment of BCNPs. As a result of no fluorescence from single BCNPs, BCNPs can be used as MPs tracing probe in a "turn-on" fluorescence mode caused by combination of BCNPs and MPs. The practical ability of BCNPs for MPs was validated in soil and aqueous models, and semi quantification was performed using ImageJ software. The described tracing method can be carried out using UV light without any complex instruments, provide an important step toward tracing MPs rapidly in natural conditions.