Mn-CDs@Pt nanozyme with high oxidase-like activity for smartphone-assisted colorimetric sensing of acrylamide

Herein, Mn-doped carbon dots (Mn-CDs) were prepared and used as a reducing agent to reduce PtCl₆ ^2- to platinum nanoparticles (Pt NPs), forming a stable nanozyme of Mn-CDs@Pt NPs. The prepared Mn-CDs@Pt nanozyme exhibited high oxidase-like activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with a low Michaelis-Menten constant (K _m) value of 0.0545 mM and a high maximum initial velocity (V _max) value of 3.42 × 10^-7 M s^-1. By exploiting the excellent oxidase-like activity of Mn-CDs@Pt nanozyme and combining the thiol-ene Michael addition between glutathione (GSH) and acrylamide (AA), a sensitive colorimetric detection interface for AA was fabricated. Using UV-vis measurement, the colorimetric sensor for AA detection displayed a broad linear detection range from 0.05 to 5000 μM and a detection limit (LOD) of 0.0371 μM. In addition, a smartphone-assisted detection of AA yielded a linear range from 5 to 5000 μM with an LOD of 4.35 μM. The colorimetric sensor was applied for AA detection in real samples, achieving satisfactory recoveries in the range of 94.8-110.4%. Moreover, the detection results of AA in real samples were in good consistency with those detected using the standard method of HPLC, suggesting that the proposed colorimetric method possesses potential for AA detection in food safety and quality monitoring.