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

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.