Time resolved fluorescence polarization anisotropy of carbonaceous particles produced in combustion systems

The size of nanometric carbonaceous particles produced in various combustion systems is determined by means of time resolved fluorescence polarization anisotropy (TRFPA). We also compare the performances of two different experimental implementations of the technique, which are complementary in terms of cost, simplicity and resolution. Both methods are first employed on standard molecules to demonstrate the reliability of the results. A study of the sizes of nanometric particles collected at the exhaust of diesel and gasoline vehicle engine, as well as from controlled laminar flames is presented. The high sensitivity (0.04 nm) achieved with the use of a streak camera as detector makes the TRFPA technique particularly suitable for characterizing nanometric particles.