Hollow MOFs-based biomimetic encoded microspheres as versatile probes for dual-mode ratiometric fluorescence sensing platform coupling instrumental and smartphone-assisted analysis of Sudan I

Background The accurate, ultrasensitive, and on-site detection of pollutants is critical for public health. As a carcinogen, Sudan I is strictly forbidden from use in food products at any levels. However, the conventional method suffers from the high instrument cost and complex procedure, resulting in poor sensitivity, low portability, and long detection time. A ratiometric fluorescence sensor offers a promising prospect for the ultra-rapid, high sensitivity, visual detection, and “point-of-care” testing. The objective of this work was to address the insufficient selectivity of fluorescence probe and enhance the recognition capability and mass transfer rate while diversifying their signal output modes. Results In this study, a novel hollow metal-organic frameworks (MOFs) structural biomimetic nanosensor was developed for the specific recognition and rapid analysis of Sudan I. The sensor separately integrated CsPbCl 1.5 Br 1.5 perovskite quantum dots and CdSe/ZnS quantum dots as dual-emission fluorophores into hollow MOFs-based molecularly imprinted polymers, acting as the recognition element and a signal carrier. The hollow architecture significantly improved mass transfer efficiency, reducing response time to 10 min. The developed nanosensor in instrumental analysis mode exhibited a linearity within the range of 2.00–200.00 μg L −1 at a method's detection limit of 1.00 μg L −1 , indicating high accuracy with recoveries of 88.00–109.65 % in real samples. Furthermore, a smartphone-based portable platform was designed for on-site intelligence detection with a good linear range (0.15–5.00 μg mL −1 ), a method's detection limit of 0.05 μg mL −1 , and recoveries ranging from 80.20 % to 109.00 %, allowing for real-time quantitative monitoring of Sudan I. Significance This study employs hollow MOFs as support materials for in-situ growth of the imprinting layer, ensuring high adsorption capability and rapid binding. The successful implementation of two detection modes provides a comprehensive solution from laboratory precision to field application. Particularly, the portable sensing system enables real-time and on-site quantitative monitoring. This work exhibits the significant potential for the high-performance chemical sensing and point-of-care detection of food contaminants.