title: Photoactivation of Luminescent Centers in Single SiO2 Nanoparticles.
abstract: Photobleaching of fluorophores is one of the key problems in fluorescence microscopy. Overcoming the limitation of the maximum number of photons, which can be detected from a single emitter, would allow one to enhance the signal-to-noise ratio and thus the temporal and spatial resolution in fluorescence imaging. It would be a breakthrough for many applications of fluorescence spectroscopy, which are unachievable up to now. So far, the only approach for diminishing the effect of photobleaching has been to enhance the photostability of an emitter. Here, we present a fundamentally new solution for increasing the number of photons emitted by a fluorophore. We show that, by exposing a single SiO2 nanoparticle to UV illumination, one can create new luminescent centers within this particle. By analogy with nanodiamonds, SiO2 nanoparticles can possess luminescent defects in their regular SiO2 structure. However, due to the much weaker chemical bonds, it is possible to generate new defects in SiO2 nanostructures using UV light. This allows for the reactivation of the nanoparticle's fluorescence after its photobleaching.
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia and Centro di Eccellenza sui Materiali Innovativi Nanostrutturati , Via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Tarpani
authors.affiliation: III. Institute of Physics, Georg August University , 37077 Göttingen, Germany.
authors.forename: Daja
authors.initials: D
authors.lastname: Ruhlandt
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia and Centro di Eccellenza sui Materiali Innovativi Nanostrutturati , Via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Latterini
authors.affiliation: III. Institute of Physics, Georg August University , 37077 Göttingen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Haehnel
authors.affiliation: III. Institute of Physics, Georg August University , 37077 Göttingen, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Gregor
authors.affiliation: III. Institute of Physics, Georg August University , 37077 Göttingen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Enderlein
authors.affiliation: III. Institute of Physics, Georg August University , 37077 Göttingen, Germany.
authors.forename: Alexey I
authors.initials: AI
authors.lastname: Chizhik
keywords: Luminescent centers; fluorescence activation; fluorescence microscopy; nano-optics; photobleaching; single molecule spectroscopy