“Turn off-on” fluorescent sensor based on quantum dots and self-assembled porphyrin for rapid detection of ochratoxin A

We report herein a “turn off-on” fluorescent sensor based on ZnCdSe quantum dots (ZnCdSe QDs) and self-assembled zinc porphyrin for sensitive and rapid detection of ochratoxin A (OTA). Using environmentally friendly dodecyl dimethyl betaine as “soft template”, zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H-23H-porphine (ZnTPyP) was self-assembled into nanorods (SA-ZnTPyP) through a green process. The OTA detection process involves two steps: (1) the fluorescence of ZnCdSe QDs is significantly quenched by SA-ZnTPyP, and (2) the combination between SA-ZnTPyP and OTA releases ZnCdSe QDs from their quenchers such that the fluorescence is recovered. Under the optimized experimental conditions, the newly developed fluorescent sensor showed a linear response in concentration range 0.5–80 ng mL−1, with a detection limit of 0.33 ng mL−1. The excellent applicability of the system has been verified in milk and coffee samples, with relative recoveries between 98.33% and 103.70%. The proposed fluorescent sensor exhibits excellent selectivity and high sensitivity, and thus could be a promising tool for on-site determination of OTA in food safety control and environmental monitoring.