Salt-template preparation of Mo₅N₆ nanosheets with peroxidase- and catalase-like activities and application for colorimetric determination of 4-aminophenol

Mo₅N₆ nanosheets were synthesized by a nickel-induced growth method and were found to possess peroxidase-like activity in acidic condition and catalase-like activity in weak basic condition. In acidic condition, Mo₅N₆ nanosheets can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H₂O₂ to form a blue color product (TMB_OX). At the co-existence of 4-aminophenol (4-AP), 4-AP can react with H₂O₂ and TMB_OX, resulting in the decrease of TMB_OX and the fading of blue color. Therefore, a facile, sensitive colorimetric method for the quantitative detection of 4-AP was developed. The linear range for 4-AP was 1.0 to 80.0 μmol⋅L^‒1 (R² = 0.999), and the detection limit was 0.56 μmol⋅L^‒1 based on 3σ/k. Resorcinol, aniline, humic acid, and common ions and anions in surface water did not interfere the determination of 4-AP. This colorimetric method was applied to measure the 4-AP in real water sample from Wulong River in Fujian Province of China. The relative standard deviation for the determination of 4-AP was ranged from 0.03 to 1.88%, and the recoveries from spiked samples were ranged between 99.2 and 107.6%. The determination results were consistent with those obtained by HPLC. Graphical abstract: