A cross-linkable phthalonitrile derivative as a precursor to synthesize nitrogen-doped carbon nanodots for Ni ion detection

The design of organic precursors with optimized molecular structures is of great importance for improving the fluorescent properties and sensing applications of heteroatom-doped carbon nanodots (CDs). Herein, we designed and synthesized a phthalonitrile derivative containing both melamine and benzoxazine moieties, which has been, for the first time, employed as a cross-linkable precursor to prepare nitrogen-doped carbon nanodots (N-CDs), showing fluorescence emission with a large Stokes shift. As a result of the good affinity between the surface functional groups of N-CD and Ni ions proven by XPS and FTIR techniques, the fluorescence emission of optimized N-CDs can be selectively quenched by Ni ions among other metal ions. Furthermore, the synthesized N-CDs are employed as fluorescent probes for the quantitative detection of Ni ions with a wide concentration range and a high sensitivity (the limit of detection approaching 1.58 nM). Overall, the current work reveals a new possibility for expanding the synthesis route and metal ion sensing of nitrogen-doped CDs.