A Platinum Nanozyme-Based Three-Channel Cross-Reactive Colorimetric Sensor Array for Rapid Discrimination of Multiple Antibiotics

The widespread use of antibiotics has raised growing concerns about residues in food and the environment, driving the demand for rapid multiantibiotic discrimination. Conventional colorimetric sensor arrays generally depend on diverse sensing materials, making their construction cumbersome. To address this, a three-channel colorimetric sensor array was constructed based on a progressive structural design of platinum-based nanozymes. Platinum nanoparticles (PtNPs), platinum nanoflowers (PtNFs), and Au@Pt nanoparticles (Au@PtNPs) were selected as sensing units. These nanozymes provide basic catalytic sites, open hierarchical structures, and core–shell interfacial electronic regulation effects, respectively, thus forming a catalytic activity gradient from simple particles to complex heterostructures. Characterization revealed significant differences in morphology, particle size, and oxidase-like catalytic efficiency among the three nanozymes. Different antibiotic molecules differentially affect the oxidase-like activity of the nanozymes, generating characteristic fingerprint-like response patterns. Combined with principal component analysis (PCA), the array achieved class discrimination of the six antibiotics. It also achieved good concentration discrimination in the range of 0.1–10 μmol·L–1. In binary to six-component mixtures in real milk matrices, the array also exhibited good discrimination capability, with blind sample accuracy reaching 100% for the limited number of blind samples. More importantly, by coupling the array with smartphone, a PCA model using the red-to-blue (R/B) ratio data effectively distinguished six antibiotics in milk, demonstrating the feasibility of on-site rapid discrimination. This study not only provides a practical strategy for rapid antibiotic residue discrimination without specific discrimination elements, but also highlights the structural gradient design of nanozymes as a general route to cross-reactive sensing.