Distance-dependent fluorescence quenching on gold nanoparticles ensheathed with layer-by-layer assembled polyelectrolytes.

We report on the preparation, characterization, and photophysical study of new fluorescent core/shell nanoparticles fabricated by electrostatic layer-by-layer assembly. On the basis of gold cores with a diameter of 13 nm, these nanocolloids possess different fluorescently labeled polymer corona layers at various distances from the surface of the core metal using nonfluorescent polyelectrolytes as spacer layers. UV-visible spectroscopy and transmission electron microscopy confirm that the particle suspensions of fluorescently labeled core/shell nanoparticles are stable at all stages of their construction. Photophysical investigations reveal strongly distance-dependent fluorescence quenching in these particle systems. The contribution of the metal core to this quenching can be assesed precisely after the gentle dissolution of the gold cores by potassium cyanide. The photophysical measurements reveal clearly that the gold nanoparticles decrease the transition probability for radiative transitions