Parasitic particle size, effect

The time-resolved monitoring and evaluation of the autocorrelation function of the emission intensity fluctuations yield information on the diffusion rate of fluorescent species. However, the experimental measurement is affected by a number of parasite side effects. First, the intensity of the focused beam is very high, which promotes photobleaching (mainly the transition to the triplet state). Hence, only a few very stable and resistant fluorophores (rhodamine dyes or BODIPY) can be employed and still an appropriate correction has to be used when evaluating the diffusion coefficients. Second, the multiple labeling of particles of finite size can generate additional problems. We will focus on some of these complications in Sects. 3.5 and 4.3. 

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