Electron multiplying CCD based detection for spatially resolved fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy (FCS) is carried out with an electron multiplying CCD (EMCCD). This new strategy is compared to standard detection by an avalanche photo diode showing good agreement with respect to the resulting autocorrelation curves. Applying different readout modes, a time resolution of 20 mu s can be achieved, which is sufficient to resolve the diffusion of free dye in solution. The advantages of implementing EMCCD cameras in wide-field ultra low light imaging, as well as in multi-spot confocal laser scanning microscopy, can consequently also be exploited for spatially resolved FCS. First proof-of-principle FCS measurements with two excitation volumes demonstrate the advantage of the flexible CCD area detection.