MoS2/Cu as a peptide/nucleotide-matrix-free laccase mimetic nanozyme for robust catalytic oxidation of phenolic pollutants

Abstract

Laccase is an effective biocatalyst for the degradation of persistent phenolic pollutants. However, its high cost and instability under harsh operational conditions hinder its applications. Hence a peptide/nucleotide-matrix-free laccase mimetic nanozyme would be attractive. Herein, MoS₂/Cu is synthesized as a laccase mimic for catalytic oxidation of phenolic pollutants. Characterization of the nanozyme by SEM-EDX, XRD, and XPS confirmed the presence of multi-oxidation state copper on MoS₂ which is consistent with the composition of natural laccase. The laccase mimetic activity of MoS₂/Cu was examined by using 2,4-dichloro phenol as a substrate which oxidized to form a colored product with 4-aminoantipyrine (λ_max = 510 nm). Surprisingly, MoS₂/Cu showed 55.6% higher activity than pristine Cu NPs at pH 7, indicating the role of MoS₂ as an effective scaffold. The catalytic reaction exhibited a lower K_m (0.11 mM) than that reported for natural laccase. MoS₂/Cu showed improved stability retaining 84.63% of its activity at 90 °C and lost only 10.93% of its activity after one month. Furthermore, it exhibited remarkable activity in the presence of different salts and alcohol stress. Notably, the nanozyme converted over 92% of phenolic substrates in 9 h. The results imply a robust performance for the remediation of phenolic compounds.