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 mu mol/L. This work may offer a new approach for developing recoverable and sensitive N-CDs-based sensors for biological and environmental applications.