(Invited) Investigation into the Photophysics and Diffusion Properties of Water Soluble Quantum Dots Using Fluorescence Correlation Spectroscopy

Because of their superior photostability and fluorescence quantum yield, quantum dots are of great interest for biological applications. Unfortunately, most commercial quantum dots require a surfactant solubilizing layer to disperse in aqueous media. This significantly increases their effective diameter and limits their appeal for single molecule studies. Thus Carboxylate capped CdTe nanoparticles, which are water soluble, represent an attractive solution. We used fluorescence correlation spectroscopy to characterize the properties of these quantum dots. Our study confirms that they have small ~ 10 nm hydrodynamic radii. It also confirms that they undergo an excitation intensity dependent blinking process characterized by a power law distribution of "on" and "off" dwell times. This power law breaks down at dwell times on the order of ~10 μs.