A smartphone-assisted colorimetric sensor for sensitive and portable sensing of methimazole based on high-entropy Prussian blue nanozymes

A HE-PBA with robust POD-like was prepared a facile co-precipitation strategy. • A smartphone-assisted colorimetric sensor was design for portable assay of MMI. • This sensor displayed high specificity and sensitivity for MMI detection. • This sensor has been triumphantly used to detect MMI in cosmetic samples. It is critical to exploit a sensitive, selective, and portable strategy for the credible detection of methimazole (MMI) for human health. Herein, high-entropy Prussian blue analogues (HE-PBAs) nanozyme were successfully fabricated by a facile co-precipitation strategy. The as-synthesized HE-PBAs possess robust peroxidase (POD)-like activity, which can trigger the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) with the assistance of H 2 O 2 , generating a conspicuous chromogenic transition from colorless to blue. However, MMI can reduce oxTMB and consume the ROS, including •OH and O 2 •− , thereby suppressing the intrinsic POD-mimicking catalytic performance of HE-PBAs. Such an inhibitory effect reduces the absorbance of the sensing system and enables the gradual fading of the blue chromogenic signal. Based on this competitive inhibition mechanism, a novel colorimetric sensing platform was constructed for quantitative MMI determination. The developed sensor achieves high sensitivity toward MMI with a detection limit of 0.032 μM. Considering its simple operation and superior sensing performance, a portable and user-friendly sensor was also designed for visual sensing of MMI by combining a common smartphone. Moreover, this colorimetric sensor has been successfully applied for MMI detection in commercial cosmetic samples, demonstrating its potential practicality. This work not only provides a cheap, user-friendly, and portable sensing platform for visual detection of MMI in resource-limited settings, but also offers a rational design strategy for HEzymes. Download: Download high-res image (152KB) Download: Download full-size image