Dual-enzyme Mn3O4@NC nanozyme for smartphone-assisted visual detection of tetracycline and nitrite

A N-doped carbon composite (Mn 3 O 4 @NC) was prepared by the calcination of Mn-TTTHA . • Mn 3 O 4 @NC exhibited dual-enzyme activities, with the competitive kinetic parameters. • A colorimetric sensor of Mn 3 O 4 @NC was established for the detection of TC and NO 2 − . • The smartphone-assisted sensing platform for TC and NO 2 − were constructed. • The sensor provided possibility for the detection of TC and NO 2 − in real environment. Accurate, reliable and visualized detection of tetracycline (TC) and nitrite (NO 2 − ) is necessary and challenging for the environment and food safety. Hence, we have developed a colorimetric strategy utilizing N-doped carbon composite (Mn 3 O 4 @NC) nanozyme for TC and NO 2 − analysis. Mn 3 O 4 @NC with oxidase-like and peroxidase-like activities is successfully prepared by the calcination process with MOF material as precursor. The dual enzyme-like property could valid catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) from colorless to blue ox-TMB, accompanied by the production of a variety of reactive oxygen species and the transformation of Mn valence state. Taking advantage of the typical reduction reaction and specific diazotization reaction between TC or NO 2 − and ox-TMB, the nanozyme announces colorimetric and ration colorimetric signals, exhibiting high performance in selectivity and anti-interference ability with corresponding limitation of detection of 0.40 μM and 1.006 μM, respectively. Moreover, by utilizing the color transition reflected in the colorimetric and ration colorimetric response processes, a smartphone assisted sensing platform based on agarose hydrogel was established to achieve one-stop, convenient and visual detection of TC and nitrite. It is worth noting that this method of visualizing and digitizing the detection process overcomes limitations of traditional detection methods and maximizes accurate detection of harmful pollutants. This strategy also provides a promising solution for accurately and reliably detecting TC and nitrite in water and food. A nanoenzyme with dual-enzyme activities was synthesized by the calcination of MOF material. This dual-enzyme activities could effectively catalyze the oxidation of colorless TMB to blue ox-TMB under the action of Mn valence state transition and generation of reactive oxygen species. Its visualized catalytic performance enabled it to be used for colorimetric/ratiometric detection of tetracycline (TC) and nitrite in real water samples with the lower limitation of detection. With the assistence of smartphone and agarose hydrogel, the one-stop, convenient and visible sensing platform was constructed, applying for the TC and nitrite in real water samples. This work provides a new strategy for accurately and reliably detecting TC and nitrite in water and food. Download: Download high-res image (130KB) Download: Download full-size image