Aggregation-disaggregation regulated fluorescence resonance energy transfer of perovskite nanocrystals for the detection of ascorbic acid

Fluorescence resonance energy transfer (FRET) from fluorescent nanoparticles to small molecules is an attractive approach for bioanalysis. It remains challenging to reversibly regulate the FRET, let alone use reversible FRET to detect ions or molecules. Here we demonstrate an aggregation/disaggregation strategy for reversible regulation of FRET based on metal–ligand coordination chemistry and redox reactions. An amino-functionalized red fluorescent (∼668 nm) perovskite nanocrystals (PNCs) was prepared as the energy donor. Fe³⁺ can coordinate with the amino groups on PNCs, resulting in the aggregation of PNCs and enhanced absorption from 600 to 700 nm on the surface of PNCs. Aggregation can reduce the distance between PNCs and Fe³⁺–amino complexes, as well as restrict rotational and translational diffusion of PNCs or Fe³⁺–amino complexes, consequently enhancing the FRET between PNCs and Fe³⁺–amino complexes. Interestingly, reductive ascorbic acid can reduce Fe³⁺ to Fe²⁺ in the complexes, leading to a weakening of absorption at 668 nm and dispersion of PNCs, resulting in the disappearance of the FRET process involved in PNCs. Based on the FRET switch, we have realized consecutive quantitative analysis of Fe³⁺ and ascorbic acid in real samples. We expect that reversible FRET process can be regulated by aggregation-disaggregation instructed by coordination and redox reactions, and that the regulation strategy could significantly expand the application scope of PNCs in fluorescence detection.