Polymer composite fluorescent hydrogel film based on nitrogen‐doped carbon dots and their application in the detection of Hg2+ ions

A simple microwave‐assisted solvothermal method was used to prepare fluorescent nitrogen‐doped carbon dots (N‐CDs) with high fluorescence quantum yield (79.63%) using citric acid and N‐(2‐hydroxyethyl)ethylenediamine as starting materials. The PVAm‐g‐N‐CDs grafted products were synthesized by amide bond formation between the carboxylic groups of N‐CDs and amine groups of polyvinylamine (PVAm). Fluorescent hydrogel films (PVAm‐g‐N‐CDs/PAM) were synthesized by interpenetration polymer network polymerization of PVAm‐g‐N‐CDs and acrylamide (AM). When used for ion detection, we found that the fluorescence of the hydrogel films was clearly quenched by addition of Hg2+. Repeatability tests on using the hydrogel films for Hg2+ detection showed that they could be applied at least three times. The PVAm‐g‐N‐CDs/PAM could serve as an effective fluorescent sensing platform for sensitive detection of Hg2+ ions with a detection limit of 0.089 μmol/L. This work may offer a new approach for developing recoverable and sensitive N‐CDs‐based sensors for biological and environmental applications.