Design and fabrication of a highly active nanoenzyme CeO2@Mn/ZIF-67 mediated by L-arginine for construction of a portable glass tube hydrogel sensor towards rapid nitrite detection

Nitrite is a kind of frequently detected inorganic pollutants in water. In order to sensitively and conveniently monitor the nitrite anytime and anywhere, colorimetric sensing method-based nanoenzymes and portably immediate detection devices become urgent. Herein, we utilized L-arginine as a catalyst and a linker to mediate the synthesis of CeO 2 on bimetallic MOFs (CeO 2 @Mn/ZIF-67), with Co and Mn were set as the central metals. Its enzyme-activated performance ( K m : 0.054 mM and V max : 64.00 μMs −1 ) was superior to most reported materials. Nitrite can diazotize with oxTMB, causing a change in the ratio of absorbance at 652 nm to absorbance at 450 nm (A 652 /A 450 ). Thus, a rapid and sensitive platform for the colourimetric detection of nitrite was established. A portable glass tube hydrogel sensor was designed inspired by the principle of disposable alcohol swabs for the first time to achieve the nitrite monitoring. When the glass tube was cut to introduce TMB and nitrite into the nanoenzymes, a noticeable colour change occurred. Attributed to the high activity of the nanoenzymes and the clever design of the detection device, the proposed method overcame the shortcomings of the traditional sensing methods such as long detection time and poor portability.