Conformable Fe-SiQDs hydrogel strips for on-site colorimetric detection of p-aminophenol in food matrices

Ensuring food safety requires reliable methods to monitor toxic contaminants like p-aminophenol (p-AP), which can migrate from plastic packaging or accumulate as veterinary drug residues in food products. However, the absence of rapid and field-deployable detection methods poses a persistent obstacle to its effective monitoring. In this work, we developed iron-doped silicon quantum dots (Fe-SiQDs) as a robust peroxidase-mimicking nanozyme and engineered a dual-mode sensing platform for p-AP detection comprising a solution-based assay for laboratory use and a hydrogel strip for on-site smartphone-assisted quantification. The solution assay achieved high sensitivity (LOD: 5.22 μM) with excellent correlation to HPLC (R² = 0.9994), while the hydrogel strip enabled quantification within 15 min without complex instrumentation. The Fe-SiQDs-based hydrogel sensor was tested on real-world food matrices including honey and bottled water, achieving accurate recoveries between 93.2% and 119.5% with high reproducibility (RSD < 2.1%). This cost-effective and field-ready system provides a practical solution for rapid screening of p-AP in food samples, offering a useful tool for food safety monitoring.