Open AccessFluorescence depletion properties of insulin–gold nanoclusters
Author(s) -
Po-Fu Chen,
ChienLiang Liu,
Lin Wan,
Kuan-Chieh Chen,
PiTai Chou,
ShiWei Chu
Publication year - 2015
Publication title -
biomedical optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.362
H-Index - 86
ISSN - 2156-7085
DOI - 10.1364/boe.6.003066
Subject(s) - nanoclusters , intersystem crossing , fluorescence , sted microscopy , population , materials science , microscopy , photochemistry , chemistry , stimulated emission , nanotechnology , optics , excited state , laser , physics , atomic physics , demography , sociology , singlet state
Insulin-gold nanoclusters exhibit outstanding biocompatibility, photostability, and fluorescence quantum efficiency. However, they have never been used in superresolution microscopy, which requires nonlinear switching or saturation of fluorescence. Here we examine the fluorescence and stimulated emission depletion properties of gold nanoclusters. Their bleaching rate is very slow, demonstrating superior photostability. Surprisingly, however, the best depletion efficiency is less than 70%, whereas the depletion intensity requirement is much higher than the expectation from a simple two-level model. Fluorescence lifetime measurement revealed two distinct lifetime components, which indicate intersystem and reverse intersystem crossing during excitation. Based on population dynamic calculation, excellent agreement of the maximal depletion efficiency is found. Our work not only features the first examination of STED with metallic clusters, but also reveals the significance of molecular transition dynamics when considering a STED labeling.