Photoinduced Dark Fraction Due to Blinking and Photodarkening Probability in Aqueous CdTe Quantum Dots

Abstract

We provide a novel approach to measure the photoinduced dark fraction due to blinking in semiconductor quantum dots in dilute aqueous solution using fluorescence correlation spectroscopy. We find that below certain threshold excitation intensity, addition of β-mercaptoethanol (BME) does not have a measurable effect on the average number of luminescent quantum dots in a diffraction-limited detection volume. However, above this threshold, it was found to increase and saturate with increasing BME concentration. From these measurements we calculated the photoinduced dark fraction due to blinking and the probability of quantum dot entering into a dark state upon photon absorption (∼10–6).