Characterization of blinking dynamics in quantum dot ensembles using image correlation spectroscopy

Quantum dots (QDs) are being increasingly applied as luminescent labels in optical studies for biophysical and cell biological applications due to their unique spectroscopic properties. However, their fluorescence "blinking" characteristics that follow power law statistics make it difficult to use QDs in some quantitative biophysical applications. We present image correlation spectroscopy (ICS) in combination with total internal reflection fluorescence microscopy as a tool to characterize blinking dynamics in QDs. We show that the rate of decay of the ICS measured ensemble correlation function reflects variation in blinking dynamics and can be used to distinguish different blinking distribution regimes. To test and confirm our hypothesis, we also analyze image time series simulations of ensembles of point emitters with set blinking statistics. We show that optimization of the temporal sampling and the number of QDs sampled is essential for detecting changes in blinking dynamics with ICS. We propose that this experimental characterization of the QD blinking statistics can actually serve as a sensitive reporter for certain quantitative biological applications.