Copper nanoparticles incorporated nitrogen-rich carbon nitride as laccase-like nanozyme for colorimetric detection of bisphenol a released from microplastics

Herein, a new strategy for laccase-like nanozyme is proposed by utilizing copper nanoparticles (Cu NPs) as the active center, carbon nitride as the skeleton and triazole groups as the cofactor. Cu NPs incorporated nitrogen-rich carbon nitride (Cu-g-C3N5) nanocomposites are found to possess excellent laccase-like activity, which can catalyze the oxidation of bisphenol A (BPA) to produce a color change in the presence of 4-aminoantipyrine. The catalytic efficiency of Cu-g-C3N5 nanocomposites is 4-fold higher than their analogue (Cu-g-C3N4 nanocomposites) without triazole groups. Cu-g-C3N5 nanocomposites also display robust catalytic activity with high temperature stability, resistance to acid and alkalinity, and long term stability. Density functional theory calculations indicate that triazole groups are beneficial to improve the stability of Cu NPs via additional Cu-N bonds and facilitate the activation of the adsorbed O2 molecules. There is a linear relationship between the absorbance and BPA concentration over the range of 0.25–25 mg L−1 with the limit of detection of 0.09 mg L−1. Finally, Cu-g-C3N5 nanocomposites are successfully applied for colorimetric detection of BPA released from polycarbonate microplastics. To the best of our knowledge, this is the first example to utilize laccase-like nanozyme for colorimetric detection of BPA.