In situ detection of soot nanoparticles by time-resolved fluorescence analysis

We present a new implementation of the time-resolved fluorescence anisotropy technique for the analysis of carbon nanoparticles directly in a Bunsen-type propane flame. By exploiting femtosecond laser excitation, UV-visible laser-induced fluorescence and time resolution of the experimental set-up, small soot nanoparticles have been identified within the flame. From the measurement of the decay time of the anisotropy ratio, we determined an ensemble-averaged diameter of the carbon particles of approximately 10 nm, with a slightly larger value in the outer edge of the flame compared to its centre.