Fluorescence and electrical resistance bimodal sensing of microplastics using sulfur-doped carbon nanoparticle/polypyrrole composites

Convenient detection assays are pressing need for assessing of microplastics (MPs) distribution in environmental samples. However, the promotion of MPs detection toward daily application is limited by complex pretreatment and instruments. This study describes a low cost detection assay for quantification of polyethylene (PE) MPs within 7 min without requiring large-scale instruments. A sulfur-doped carbon nanoparticle encapsulated with polypyrrole (S-CNPs/PPy) was prepared to fabricate modified conducting glass slices (MCGs) through a drip coating process. Both fluorescence and resistance signals were enhanced by the addition of PE MPs. The enhancement of fluorescence intensity was attributed to the surface environment of S-CNPs/PPy changed through interaction between S-CNPs/PPy and PE MPs, meanwhile the low conductivity of PE MPs increased the electrical resistance. The use of smartphone and multimeter are convenience for daily sensing. The fluorescence/electrical resistance bimodal sensing performances were evaluated using various amounts of PE MPs and applied in river and sea samples. The combination of fluorescence and electrical resistance signals provides a simple and individual way compared with instrument analysis of PE MPs, and holds potential to achieve monitoring of PE MPs in complex scene.