Halogen Exchange‐Based Perovskite Nanosensor for the Visual Detection of Penicillin

The overuse of antibiotics has emerged as a critical global public health challenge. On‐site antibiotic detection is of great significance for promoting rational antibiotic use, ensuring food safety, and safeguarding public health. In this work, a visual sensing strategy based on dynamic bandgap modulation of perovskite nanocrystals (PNCs) is developed for the on‐site detection of penicillin. The hydrolysis products of penicillin react with iodine to generate iodide ions, which induce lattice structural regulation in CsPbBr 3 PNCs through ion exchange, leading to a pronounced redshift in fluorescence emission and an observable fluorescence color change. The concentration of penicillin exhibits a strong correlation with the maximum emission wavelength shift of PNCs, enabling direct visual detection through naked‐eye observation of fluorescence color changes without reliance on complex or costly instrumentation. This method demonstrates high specificity, enabling effective discrimination between penicillin and cephalosporin. What is more, no complex pretreatment is required, allowing for on‐site detection of penicillin within 60 min. This method has been successfully applied to detecting penicillin in pharmaceuticals, foods, and environmental samples, offering a robust strategy for efficient and rapid screening of penicillin residues in complex matrices.