Ratiometric Colorimetric Detection of Nitrite Realized by Stringing Nanozyme Catalysis and Diazotization Together

Abstract

Due to the great threat posed by excessive nitrite in food and drinking water to human health, it calls for developing reliable, convenient, and low-cost methods for nitrite detection. Herein, we string nanozyme catalysis and diazotization together and develop a ratiometric colorimetric approach for sensing nitrite in food. First, hollow MnFeO (a mixture of Mn and Fe oxides with different oxidation states) derived from a Mn-Fe Prussian blue analogue is explored as an oxidase mimic with high efficiency in catalyzing the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation to blue TMBox, presenting a notable signal at 652 nm. Then, nitrite is able to trigger the diazotization of the product TMBox, not only decreasing the signal at 652 nm but also producing a new signal at 445 nm. Thus, the analyte-induced reverse changes of the two signals enable us to establish a ratiometric colorimetric assay for nitrite analysis. According to the above strategy, facile determination of nitrite in the range of 3.3–133.3 μM with good specificity was realized, providing a detection limit down to 0.2 μM. Compared with conventional single-signal analysis, our dual-signal ratiometric colorimetric mode was demonstrated to offer higher sensitivity, a lower detection limit, and better anti-interference ability against external detection environments. Practical applications of the approach in examining nitrite in food matrices were also verified.

Fe-Single-Atom Nanozyme Catalysts for Sensitive and Selective Detection of Nitrite via Colorimetry and Test Strips

“…It is reported that TMB and oxidized TMB (TMBox) may react with nitrite through two different reaction paths and mechanisms: diazotization interaction , and redox interaction. To confirm these, a series of experiments were performed.…”

Bifunctional Mn-Doped N-Rich Carbon Dots with Tunable Photoluminescence and Oxidase-Mimetic Activity Enabling Bimodal Ratiometric Colorimetric/Fluorometric Detection of Nitrite

“…17,18 Besides, in some cases, logical operation on these signal outputs can be made to further boost the analytical sensitivity. 19 Consequently, multimodal methods are able to benefit the measurement of targets via expanded usage scenario and enhanced reliability as well as improved sensitivity, yet how to rationally design strategies to achieve the multimode perception of analytes is a great challenge. Nanomaterials with bioenzyme-like catalytic activities (nanozymes) have been proposed as a new generation of artificial enzymes in recent years, 20−23 exhibiting the superiorities of good stability, low cost, and easy-to-regulate activity compared to bioenzymes.…”

“…One can select an appropriate mode from multimodal methods to achieve the monitoring of targets according to matrix characteristics and testing environments, where traditional single-mode sensors may fail. On the other hand, the results obtained from different modes can be verified against each other, effectively improving the accuracy and reliability and avoiding false results. , Besides, in some cases, logical operation on these signal outputs can be made to further boost the analytical sensitivity . Consequently, multimodal methods are able to benefit the measurement of targets via expanded usage scenario and enhanced reliability as well as improved sensitivity, yet how to rationally design strategies to achieve the multimode perception of analytes is a great challenge.…”