Ratiometric fluorescence sensing based on rare-earth upconversion nanoparticles for the rapid identification of antioxidant capacity

Based on the internal filtration effect between upconversion nanoparticles and square acid-FeIII(SA-FeIII), this method was developed for the rapid identification of total antioxidant capacity of different fruits without complex modification on the surface of upconversion nanoparticles. The near-infrared light excitation of rare-earth upconversion can effectively avoid food fluorescence and the photobleaching effect; thus, the components to be detected in the samples can be monitored real time without a complex extraction process. Due to the instability of the antioxidants at room temperature, the short time required for this reaction (6 min) will facilitate the study of the true antioxidant power of the samples. This method is simple and responds well to the main antioxidants of fruits and vegetables with a detection limit of 0.1 μmol L−1, such as ascorbic acid, polyphenols, and anthocyanin, and it shows good linearity in the concentration range of 0–1.0 mmol L−1.