title: Assessing the blinking state of fluorescent quantum dots in free solution by combining fluorescence correlation spectroscopy with ensemble spectroscopic methods.
abstract: The current method for investigating the blinking behavior is to immobilize quantum dots (QDs) in the matrix and then apply a fluorescent technique to monitor the fluorescent trajectories of individual QDs. So far, no method can be used to directly assess the blinking state of ensemble QDs in free solution. In this study, a new method was described to characterize the blinking state of the QDs in free solution by combining single molecule fluorescence correlation spectroscopy (FCS) with ensemble spectroscopic methods. Its principle is based on the observation that the apparent concentration of bright QDs obtained by FCS is less than its actual concentration measured by ensemble spectroscopic method due to the QDs blinking. We proposed a blinking index (Kblink) for characterizing the blinking state of QDs, and Kblink is defined as the ratio of the actual concentration (Cb,actual) measured by the ensemble spectroscopic method to the apparent concentration (Cb,app) of QDs obtained by FCS. The effects of certain factors such as laser intensity, growth process, and ligands on blinking of QDs were investigated. The Kblink data of QDs obtained were successfully used to characterize the blinking state of QDs and explain certain experimental results.
authors.affiliation: School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, P. R. China.
authors.forename: Chaoqing
authors.initials: C
authors.lastname: Dong
authors.forename: Heng
authors.initials: H
authors.lastname: Liu
authors.forename: Jicun
authors.initials: J
authors.lastname: Ren