Cu-MOF/C3N5 as a laccase-like nanozyme for colorimetric detection of antioxidants in electronic cigarettes

Abstract

Herein, we prepare a framework consisting of a Cu-MOF anchored on a graphitic carbon nitride (Cu-MOF/C₃N₅) nanomaterial for antioxidant sensing. The photocatalytic efficiency of the Cu-MOF was statistically increased by doping with g-C₃N₅. Cu-MOF/C₃N₅ has been shown to possess prominent laccase-like and catalase (CAT)-like activities, and can catalyze the oxidation of the antioxidants butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ) to generate a color change in the presence of 4-aminoantipyrine (4-AP). Furthermore, the catalytic efficiency of the Cu-MOF/C₃N₅ nanozyme under near infrared (NIR) stimulation is 4 times higher than that obtained without NIR stimulation. On the one hand, the Cu-MOF/C₃N₅ with the CAT-like plasmonic nanozyme generated an abundance of high-energy hot carriers under NIR stimulation to promote the decomposition of H₂O₂ to generate abundant oxygen (O₂); on the other hand, the photothermal effect induced by the localized surface plasmon resonance (LSPR) on Cu-MOF/C₃N₅ significantly improved the reaction kinetics and thus resulted in an obviously enhanced laccase-like activity. There are linear relationships between the absorbance and BHA and TBHQ concentrations in the ranges of 0.033–2.67 mM and 0.033–2.67 mM with limits of detection of 0.0113 mM and 0.027 mM. Finally, Cu-MOF/C₃N₅ is successfully employed for colorimetric detection of BHA and TBHQ in electronic cigarettes.