Photoswitchable semiconductor nanocrystals with self-regulating photochromic Förster resonance energy transfer acceptors

This is the authors' abstract. We don't add key points for this paper.

Photoswitchable molecules and nanoparticles constitute superior biosensors for a wide range of industrial, research and biomedical applications. Rendered reversible by spontaneous or deterministic means, such probes facilitate many of the techniques in fluorescence microscopy that surpass the optical resolution dictated by diffraction. Here we have devised a family of photoswitchable quantum dots (psQDs) in which the semiconductor core functions as a fluorescence donor in Förster resonance energy transfer (FRET), and multiple photochromic diheteroarylethene groups function as acceptors upon activation by ultraviolet light. The QDs were coated with a polymer bearing photochromic groups attached via linkers of different length. Despite the resulting nominal differences in donor–acceptor separation and anticipated FRET efficiencies, the maximum quenching of all psQD preparations was 38±2%. This result was attributable to the large ultraviolet absorption cross-section of the QDs, leading to preferential cycloreversion of photochromic groups situated closer to the nanoparticle surface and/or with a more favourable orientation. Photochromic Förster resonance energy transfer endows nanosensors with photoswitchable fluorescence properties. Diaz et al. present a system with two photostationary end states, one of which exhibits constant quenching of the quantum dot donor independent of its mean distance to the photochromic acceptors.