Microwave-Assisted Rapid Synthesis of Near-Infrared Light-Responsive Pd Single-Atom Nanozymes for Colorimetric Detection of Acetylcholinesterase Activity

Single-atom nanozymes (SAzymes) have been widely utilized as promising sensing platforms for numerous analytical applications. However, the preparation of SAzymes usually needs tedious heating treatment, and their enzyme-mimicking activities are still difficult to modulate in a simple way to meet the requirement under special conditions, both of which restrict their practical applications. To overcome these issues, we herein successfully prepared one kind of typical SAzyme, Pd-N-C, in as short as 4 min via facile and efficient microwave-assisted pyrolysis. Pd-N-C showcased excellent oxidase-like activity under near-infrared (NIR) light irradiation, which can also be regulated by light switching. The activation of dissolved oxygen into reactive oxygen species (O₂^•- and ¹O₂) by Pd-N-C subsequently enabled the oxidation of the colorless substrate <i>o</i>-phenylenediamine to yellow product 2,3-diaminophenazine (DAP). Taking advantage of the NIR light-responsive oxidase-like activity of Pd-N-C, sensitive colorimetric assays were developed for the detection of acetylcholinesterase (AChE) activity and its inhibitor based on the cascade catalytic system by combining Pd-N-C with AChE. The green synthesis approach and intelligent modulation of the catalytic activity of SAzymes presented here is thus believed to provide a novel perspective for rational synthesis and manipulation of nanozymes for broader analytical applications.