Radiative and nonradiative rates of phosphors attached to gold nanoparticles

Gold nanoparticles manipulate the quantum efficiency of phosphorescent molecules, which are attached via biotin-streptavidin recognition at a distance of 4 nm to the nanoparticle surface. Time-resolved luminescence spectroscopy reveals an increase in the radiative as well as in the nonradiative rate of the phosphorescent molecules upon binding to gold nanoparticles. The increase in the radiative rate alone would lead to an increased luminescence quantum yield. However, this effect is outweighed by the distinct enhancement of the nonradiative rate due to energy transfer, resulting in an overall quenching of the luminescence.