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

Abstract

Here, a sensitive and selective strategy for the detection of nitrite via colorimetry and test strips was developed based on Fe-single-atom catalysts (Fe SACs) through the oxidation–reduction and diazotization reactions. Fe SACs possess excellent oxidase-like (OXD) catalytic activity, which can catalyze the oxidation of the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue TMBox with the appearance of an obvious absorbance peak at 652 nm in the presence of oxygen. With the addition of nitrite (NO2 –), the oxidation–reduction and diazotization reactions between TMB/TMBox and nitrite can induce the color of the solution to change from blue to green and finally to yellow, with the increase of the peak at 445 nm. Based on this strategy, a dual-signal-ratio colorimetric detection method for nitrite was proposed. Within the concentration range of 1–120 μM, the ratio of A 652/A 445 has a favorable linear relationship with the logarithm concentration of NO2 –, with a detection limit of 0.238 μM. By combining smartphones with the colorimetric method, a more intuitive, visual, and convenient test strip detection platform was developed, which can be utilized for the detection of nitrite within 2–200 μM. The analysis strategy based on the Fe-single-atom nanozyme catalysis integrated with the specific redox/diazotization reaction not only provides a dual-signal ratio sensing with good sensitivity but holds the advantage of good selectivity for the utilization of the specific chemical reaction, which has broad application prospects in food safety supervision and food screening.

Perspectives for the Role of Single-Atom Nanozymes in Assisting Food Safety Inspection and Food Nutrition Evaluation

“…Nitrite is a common food additive, and prolonged intake of nitrite-containing foods can affect the body’s ability to transport blood oxygen. Liu et al established a novel sensor for the detection of nitrite according to color change caused by the oxidation–reduction and diazotization reactions of Fe SAzymes and TMB . Moreover, the intuitive and convenient colorimetric assay based on a test strip platform was proposed by combining Fe SAzymes/TMB/nitrite with smartphones for the detection of nitrite in the wide linear range of 2–200 μM with the advantage of good selectivity in the utilization of specific substances, indicating that SAzymes have promising applications for food-specific detection (Figure C).…”

Polydopamine Surface Engineering of Iron Single-Atom Nanozyme: a Novel Strategy for Doxorubicin Immobilization, Tumor Microenvironment Remodeling and Synergistic Multimodel Therapy

“…The detailed synthesis process for Fe SAN NPs is described in our previous work 34 . 1 mg Fe SAN was dispersed in 20 mL tris (hydroxymethyl) aminomethane hydrochloride (Tris-HCl, pH 8.5) and 1 mg DA was added during agitation.…”

Rational Integration of Nanozyme Probe and Smartphone Device for On‐Site Analysis

“…Subsequently, by detecting the changes through a specific smartphone App, quantitative analysis could be realized in a convenient way. [33][34][35][36] In fact, there have been featured reviews on the construction and various applications of nanozyme-based sensors. [37][38][39] Nevertheless, few of them concentrate on the integrated analysis systems composed of nanozyme sensing platforms and smartphone processing procedures.…”