Saturation of Two-Photon Excitation Provides Insight into the Effects of a Quantum Dot Blinking Suppressant:A Fluorescence Correlation Spectroscopy Study

摘要

Quantum dots are now extensively used as luminescent tags for biological and chemical applications;however,their propensity to display intermittent luminescence(aka blinking)has limited their use in quantitative assays.Various surface active redox agents,such as beta-mercaptoethanol,have been posited as antiblinking agents to help mitigate this challenge.We have examined the effect of beta-mercaptoethanol on the luminescence intermittency of CdSe/ZnS quantum dots using fluorescence correlation spectroscopy.We find that beta-mercaptoethanol lowers the quantum dot brightness and therefore lowers the probability of observing blinking but does not otherwise inhibit intermittent luminescence.Based on changes in fluorescence correlation data and excited-state lifetimes,we propose that the partitioning of beta-mercaptoethanol onto the quantum dot surfaces increases nonradiative de-excitation rates.This behavior appears to be independent of the quantum dot surface passivation layer or the solution contents.