Phosphorescent Naphthalene-Doped Carbon Nitride Quantum Dots for Selective Detection of Polyamide Microplastics

Fluorescent dye labeling is a visual method for the detection of microplastics (MPs). However, the interference from the background fluorescence in complex environmental samples results in overestimation of the MP number, and the nonspecific fluorescent dye cannot selectively detect a single type of MPs. Herein, phosphorescent naphthalene-doped carbon nitride quantum dots (NDCNQDs) were prepared via incomplete condensation of urea with 1,5-diaminonaphthalene at 250 °C and used as a specific dye to stain polyamide (PA) MPs via hydrogen bonding. A phosphorescence imaging method for the selective detection of PA MPs was proposed. Benefitting from the long lifetime of phosphorescence, the interference from the background fluorescence in environmental samples was avoided. The recoveries for PA MPs in pond water samples and pond mud samples were 91.2-108.4%. PA MPs in environmental samples (e.g., streamwater, sediment, house dust) were analyzed without complicated pretreatment. This work provides a strategy for the specific detection of PA MPs in environmental samples.