Difunctional Cu-doped carbon dots: catalytic activity and fluorescence indication for the reduction reaction of p-nitrophenol

Herein, we report the preparation of Cu-doped carbon dots (CDs) through a one-step hydrothermal carbonization using CuCl2·2H2O and ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) as precursors. As confirmed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), the Cu species chelates with the carbon matrix through Cu–N complexes. Using p-nitrophenol reduction as a model reaction, the catalytic activity and performance as a fluorescence indicator in the catalytic process are further examined. Results show that the synergistic effect, which may stem from the highly efficient catalysis activity of Cu and the electron-enhanced effect from graphite-like CDs, is responsible for the catalytic activity of p-nitrophenol hydrogenation reaction with the pseudo-first-order rate constant being 1.2 × 10−2 s−1. Interestingly, the catalyzed reduction process of p-nitrophenol can be tracked using fluorescence spectra of Cu-doped CDs by means of the Inner Filter Effect (IFE). The unique properties of the difunctional Cu-doped CD catalyst as well as the IFE sensing strategy will provide an ideal platform to monitor the catalytic processes.