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 nano -composites) 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 cal-culations 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.