Identification and quantification of polyethylene microplastics with sulfur-doped carbon nanoparticles in fluorescence mode and construction of paper-based analytical method

Microplastics (MPs) pollution has become a vital issue of worldwide concern owing to its associated hazards and the ubiquitous accumulation of MPs particles, which is correlated to their small sizes. Rapid identification and quantification of MPs represents an ongoing challenge in the field of environmental research. In this work, we prepared a fluorescence nanoprobe for identifying polyethylene (PE) MPs and developed a readily available method for the fast quantification of PE MPs in fluorescence mode. A kind of sulfur-doped carbon nanoparticles (S-CNPs) was prepared using nitrated pyrene and dithiosalicylic acid as precursors via a solvothermal process. S-CNPs showed no fluorescence emission in the solid state, whereas visible fluorescence was observed by labeling PE MPs. The surface environment-dependent emission of S-CNPs is an important factor in explaining the different emissions of different types of MPs, such as PE, polyvinyl chloride (PVC), and polystyrene (PS) for MPs identification. Notably, the distinction between PE and polypropylene (PP) was achieved using these S-CNPs according to their different staining efficiencies. Owing to its fast staining ability, a paper-based method for PE MPs quantification in water samples was developed using a simple vacuum-assisted suction filtration method and filter paper soaked with S-CNPs. Utilized as a readily available identification and quantification platform, these S-CNPs have great potential and could pave the way for MPs monitoring.