Synthesis and Characterization of Photoswitchable Fluorescent Silica Nanoparticles

Abstract

We have designed and synthesized a new functional (amino reactive)highly efficient fluorescent molecular switch (FMS) with a photochromicdiarylethene and a rhodamine fluorescent dye. The reactive group in thisFMS -N-hydroxysuccinimide ester- allows selective labeling of aminocontaining molecules or other materials. In ethanolic solutions, thecompound displays a large fluorescent quantum yield of 52% and alarge fluorescence modulation ratio (94%) between two states that maybe interconverted withred and near-UV light. Silica nanoparticles incorporatingthe new FMS were prepared and characterized, and their spectroscopicand switching properties were also studied. The dye retained itsproperties after the incorporation into the silica, thereby allowing lightinducedreversible high modulation of the fluorescence signal of a singleparticle for up to 60 cycles, before undergoing irreversible photobleaching.Some applications of these particles in fluorescence microscopy arealso demonstrated. In particular, subdiffraction images of nanoparticleswere obtained, in the focal plane of a confocal microscope.