Ultrabright Supramolecular Beacons Based on the Self-Assembly of Two-Photon Chromophores on Metal Nanoparticles

Abstract
Silver nanoparticles coated with a self-assembled layer of ∼2500 chromophoric alkylthiol ligands, that exhibit a huge per particle two-photon absorption cross section (2.7 × 10-45 cm4 s photon-1) and a high fluorescence quantum yield (0.33), are reported. Polyfunctionalized variants of these nanoparticles have been produced that show reasonable solubility in water/ethanol mixtures. By virtue of the large number of tethered chromophores, these particles act as strongly two-photon absorbing nanobeacons and may have applications in fluorescence imaging and sensing.