Depolymerized phosphorus-doped polymeric carbon nitride: A mercury (II) ion fluorescent probe

The fluorescence quenching effect of polymeric carbon nitride-based materials can be efficiently applied to the rapid detection of Hg²⁺. Herein, we chose dicyandiamide and sodium hypophosphite as precursors to prepare bulk phosphorous-doped polymeric carbon nitride through thermal polycondensation, and then a one-step hydrothermal treatment caused the depolymerization of the bulk products and the formation of the nanorod-like structures. The depolymerization resulted in the good aqueous colloidal stability of the polymeric carbon nitride-based derivative, and phosphorus-doping significantly improved its fluorescence. More terminal amino and abundant surface hydroxyl groups led to the enhanced selective fluorescence quenching of Hg²⁺ by the depolymerized products. Therefore, the depolymerized phosphorous-doped polymeric carbon nitride with a fluorescence quantum yield of 23.2% showed excellent Hg²⁺ detection capability. The limit of detection of the depolymerized polymeric carbon nitride to Hg²⁺ can reach 0.74 nmol L^?1. And the depolymerized products also showed good accuracy in the Hg²⁺ detection of shrimp samples. This work broadens the scope of polymeric carbon nitride-based heavy metal ion fluorescent probes, and provides a new roadmap for the highly selective determination of Hg²⁺.