title: Photoswitchable semiconductor nanocrystals with self-regulating photochromic Förster resonance energy transfer acceptors.
abstract: 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.
authors.affiliation: Laboratory of Cellular Dynamics, Max Planck Institute for Biophysical Chemistry, am Fassberg 11, 37077 Göttingen, Germany.
authors.forename: Sebastián A
authors.initials: SA
authors.lastname: Díaz
authors.affiliation: 1] Laboratory of Cellular Dynamics, Max Planck Institute for Biophysical Chemistry, am Fassberg 11, 37077 Göttingen, Germany [2] Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CIHIDECAR, CONICET, 1428 Buenos Aires, Argentina.
authors.forename: Florencia
authors.initials: F
authors.lastname: Gillanders
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CIHIDECAR, CONICET, 1428 Buenos Aires, Argentina.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Jares-Erijman
authors.affiliation: Laboratory of Cellular Dynamics, Max Planck Institute for Biophysical Chemistry, am Fassberg 11, 37077 Göttingen, Germany.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Jovin