Valence-Engineered Oxidase-Mimicking Nanozyme with Specificity for Aromatic Amine Oxidation and Identification

Oxidase-mimicking nanozymes with specificity for catalyzingoxidationof aromatic amines are of great significance for recognition of aromaticamines but rarely reported. Herein, Cu-A nanozyme (synthesized withCu(2+) as a node and adenine as a linker) could specificallycatalyze oxidation of o-phenylenediamine (OPD) inBritton-Robinson buffer solution. Such a specific catalyticperformance was also corroborated with other aromatic amines, suchas p-phenylenediamine (PPD), 1,5-naphthalene diamine(1,5-NDA), 1,8-naphthalene diamine (1,8-NDA), and 2-aminoanthracene(2-AA). Moreover, the presence of salts (1 mM NaNO2, NaHCO3, NH4Cl, KCl, NaCl, NaBr, and NaI) greatly mediatedthe catalytic activity with the order of NaNO2 < blank & AP; NaHCO3 < NH4Cl & AP; KCl & AP;NaCl < NaBr < NaI, which was due to anions sequentially increasinginterfacial Cu+ content via anionic redox reaction, whilethe effect of cations was negligible. With the increased Cu+ content, K (m) decreased and V (max) increased, indicating valence-engineered catalyticactivity. Based on high specificity and satisfactory activity, a colorimetricsensor array with NaCl, NaBr, and NaI as sensing channels was constructedto identify five representative aromatic amines (OPD, PPD, 1,5-NDA,1,8-NDA, and 2-AA) as low as 50 & mu;M, quantitatively analyze singlearomatic amine (with OPD and PPD as model analysts), and even identify20 unknown samples with an accuracy of 100%. In addition, the performancewas further validated through accurately recognizing various concentrationratios of binary, ternary, quaternary, and quinary mixtures. Finally,the practical applications were demonstrated by successfully discriminatingfive aromatic amines in tap, river, sewage, and sea water, providinga simple and feasible assay for large-scale scanning aromatic aminelevels in environmental water samples.

Automated summary

In this study, a Cu-A nanozyme was synthesized and found to catalyze the oxidation of aromatic amines with high specificity. A colorimetric sensor array was also constructed to detect and identify aromatic amines with high accuracy. The practical application of this method in environmental water samples was demonstrated.