Molecular-level biomimetic integration of phosphorus-doped graphene quantum dots with silver nanoparticles for highly stable and active nanozymes: Application in ultrasensitive ascorbic acid detection.

Overcoming the persistent instability of silver-based nanomaterials-namely their susceptibility to oxidation and aggregation-this work introduces a molecularly engineered platform based on arginine/aspartic acid-functionalized phosphorus-doped graphene quantum dots (RDP-GQDs). The rationally designed nanoplatform simultaneously mediates the one-step synthesis of silver nanozymes and constructs a robust heterointerface integrated with a built-in Schottky junction, thereby reinforcing structural durability and promoting interfacial charge transfer. In contrast to conventional nanozyme architectures that often trade off activity for stability, the RDP-GQD-enabled synthesis yields Ag nanostructures with exceptional resistance to oxidative and aggregative degradation, preserving full catalytic performance over extended durations. The resulting Ag@RDP-GQD heterostructure exhibits superior enzyme-like catalysis, with peroxidase-mimicking activity reaching 285.58 U·mg-1-1.14-fold that of native horseradish peroxidase-and oxidase-like activity of 105.58 U·mg-1, representing a 5.65-fold enhancement over choline oxidase. Capitalizing on this robust peroxidase activity, we constructed a sensitive colorimetric assay for ascorbic acid based on a radical-mediated mechanism. The sensor operates across a broad linear range (0.1-70 μM) with a detection limit as low as 0.039 μM and performs reliably in complex fruit matrices. Beyond its analytical performance, this study establishes a molecularly orchestrated design paradigm that converges reduction, passivation, and interfacial engineering into a unified nanoplatform. The strategy offers a broadly applicable route to fabricating high-performance metallic nanozymes with tailored stability and activity, opening new avenues in catalysis, biomedical diagnostics, and environmental sensing.