Fe single atoms encapsulated in N, P-codoped carbon nanosheets with enhanced peroxidase-like activity for colorimetric detection of methimazole

Abstract

Excessive use of antithyroid drug methimazole (MMI) in pharmaceutical samples can cause hypothyroidism and symptoms of metabolic decline. Hence, it is urgent to develop rapid, low cost and accurate colorimetric method with peroxidase-like nanozymes for determination of MMI in medical, nutrition and pharmaceutical studies. Herein, Fe single atoms were facilely encapsulated into N, P-codoped carbon nanosheets (Fe SAs/NP-CSs) by a simple pyrolysis strategy, as certified by a series of characterizations. UV–vis absorption spectroscopy was employed to illustrate the high peroxidase-mimicking activity of the resultant Fe SAs/NP-CSs nanozyme through the typical catalysis of 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. The catalytic mechanism was scrutionously investigated by the fluorescence spectroscopy and electron paramagnetic resonance (EPR) tests. Additionally, the introduced MMI had the ability to reduce the oxidation of TMB (termed oxTMB) as a peroxidase inhibitor, coupled by fading the blue color. By virtue of the above findings, a visual colorimetric sensor was established for dual detection of methimazole (MMI) with a linear scope of 5–50 mM and a LOD of 1.57 mM, coupled by assay of H2O2 at a linear range of 3–50 mM. According to the irreversible oxidation of the drug, its screening with acceptable results was achieved on the sensing platform even in commercial tablets The Fe SAs/NP-CSs nanozyme holds great potential for clinical diagnosis and drug analysis.