Single fluorescent gold nanoclusters

C T Yuan,W C Chou,J L Shen,C A Lin,J Tang,D S Chuu,W H Chang

doi:10.1364/oe.17.016111

Abstract

Both ensemble and single-molecule measurements were performed to explore the fluorescence properties of Au nanoclusters (NCs). Photoinduced fluorescence enhancement was observed for ensemble NCs in solution, but photobleaching was found at ambient environments. At the single-molecule level, fluorescence blinking and single-step photobleaching were observed. Furthermore, their time-resolved fluorescence shows a single exponential decay with a lifetime of approximately 7 ns and is insensitive to changes in fluorescence intensity. The lifetime distribution is more homogeneous within ensemble Au NCs as compared to CdSe QDs. Therefore, Au NCs have potential applications as nontoxic fluorescent labels for lifetime-based imaging microscopy. However, their low quantum yields and poor photostability are disadvantageous factors, which require further improvement.

Highlights

Nanomaterials including metals and semiconductors have attracted much attention due to their unique optical properties for fundamental research and potential applications in biological labeling [1]
Noble-metal nanoparticles (NPs) with sizes ranging from 10 nm to 100 nm have been investigated extensively
The mean separation between NCs was larger than excitation laser spots, individual NCs can be monitored by far-field laser scanning confocal microscopy (MicroTime 200, PicoQuant)

Summary

Introduction

Nanomaterials including metals and semiconductors have attracted much attention due to their unique optical properties for fundamental research and potential applications in biological labeling [1]. Noble-metal nanoparticles (NPs) with sizes ranging from 10 nm to 100 nm have been investigated extensively They exhibit strong optical absorption and scattering in the visible range as caused by collective oscillation of free electrons within the NPs (called localized surface plasmon resonance, LSPR) [2]. Such strong LSPR effects offer many potential applications, including biological markers and sensors, even down to the singleparticle levels [3,4]. In this case, Au NPs were commonly used because of their biocompatibility, non-toxicity, and photostability. In this study of fluorescence properties of Au NCs, we report our ensemble and single-particle measurements

Sample synthesis and experiments

Results and discussion

Conclusions