Sulfur-coordinated Cu single-atom nanozymes with enhanced oxidase-like activity for ultra-wide-range colorimetric detection of D-penicillamine

Single-atom nanozymes exhibit high catalytic efficiency, which is strongly determined by the coordination environment of metal centers and the structure of the supporting carbon matrix. Herein, a series of sulfur-coordinated copper single-atom nanozymes with atomically dispersed Cu-N x sites was synthesized via pyrolysis of zeolitic imidazolate framework-8 precursors co-encapsulating sodium copper chlorophyllin (SCC) and L -cysteine. SCC provided Cu-N 4 motifs, stabilizing atomically dispersed Cu sites during pyrolysis. L -cysteine plays a multifaceted role by introducing Cu-S coordination, regulating carbon framework size, and generating defect-rich structures, collectively enhancing oxidase-like activity. The optimized nanozyme exhibited a Michaelis-Menten constant of 0.28 mM and a maximum reaction rate of 6.73 × 10⁻ 8 M·s⁻ 1 , indicating strong substrate affinity and rapid catalytic turnover. Using this nanozyme, a colorimetric sensor for D -penicillamine ( D -PA) was developed, achieving an ultra-wide detection range from 0.5 to 3000 μM through a segmented detection strategy, with a low detection limit of 0.279 μM and recoveries of 92.7–107.4% in river water samples. This work demonstrates a robust sulfur-coordination strategy for high-performance single-atom nanozymes and provides a practical platform for monitoring pharmaceutical pollutants over an ultra-wide concentration range.