Fluorescence Correlation Spectroscopy of Macromolecules Using Maximum Entropy

Semiconductor quantum dots (QDs) have attracted wide interest in chemical sensing applications such as bio-imaging because of their unique size-dependent properties and robust luminescence.1-3 To dissolve semiconductor QDs in water, their surfaces are coated with hydrophilic groups. Various ligands are then bound to the surface of the QDs in order to bind them to specific compounds. These surface treatments increase the nonspecific binding of QDs and can cause their aggregation.4-6 Fluorescence correlation spectroscopy (FCS) is a sensitive analytical method that measures the concentration and diffusion coefficient of fluorescent molecules by analyzing the flu-orescence intensity fluctuation (based on photon count correlations) that occurs as the molecules pass through the laser focus.7-10