Distance dependent fluorescence quenching and enhancement of gold nanoclusters by gold nanoparticles.

The interaction between fluorescent gold nanoclusters (AuNCs) and gold nanoparticles (AuNPs) has been investigated. It was observed that the fluorescence of AuNCs was remarkably quenched when direct contact with AuNPs. The fluorescence quenching of AuNCs by AuNPs was dynamic quenching and exhibited size-dependent property. A larger size of AuNPs displayed a stronger quenching effect and gave a larger quenching constant. When a silica spacer shell was introduced between AuNPs and AuNCs, a fluorescence enhancement of AuNCs by Au@SiO2 NPs was observed. The fluorescence enhancement was strongly dependent on the separation distance between the AuNPs and the AuNCs. A maximal enhancement of 3.72 times was observed when Au@SiO2 NPs have a silica shell thickness of 12nm. This nanocomposite consisting of relatively nontoxic AuNPs and AuNCs may have a potential application in developing novel fluorescent sensor.