Luminescence quenching of pyrene-labelled fluorescent dendrons by surface anchoring of ruthenium nanoparticles

Hybrid nanostructures, comprising ruthenium nanoparticles (Ru NPs) and Fréchet-type dendrons of first (G1) and second (G2) generations bearing two and four pyrene units, respectively, and a carboxylic acid group as an anchoring function, have been prepared by taking advantage of the organometallic approach and ligand exchange. Their optical properties have been studied by absorption and fluorescence spectroscopy and compared with those of their counterparts prepared under the same conditions but with pyrene acetic acid and pyrene butyric acid as fluorophores. Pyrene-labelled Fréchet-type dendrons display more pyrene units at a longer distance from the Ru surface than pyrene acetic acid and pyrene butyric acid fluorophores. Interestingly, and unlike pyrene acetic acid- and pyrene butyric acid-derived nanohybrids, the dendron-functionalized Ru NPs exhibit significant to efficient quenching of the pyrene fluorescence (67% for G2 and 94% for G1 with respect to the free dendrons). The quenching effect of the Ru metallic cores on the fluorophore units opens up new prospects for the use of such nanohybrids as antennas for photocatalytic applications.