1,721,037 research outputs found
Time resolved fluorescence polarization anisotropy of carbonaceous particles produced in combustion systems
No full textThe 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
On detection of nanoparticles below the sooting threshold
No full textIn this communication we have examined the presence of nanoparticles in laminar premixed ethylene flames below soot formation by probe sampling/scanning mobility particle sizer (SMPS). For this purpose, we have measured the size distribution function of particles produced in ethylene/air premixed flames, analyzing the effect of neglecting diffusion losses in the sampling–detection system. We also extended the distribution function determined by the instrument software to a particle diameter below 3 nm
Characterization of ultrafast fluorescence from nanometric carbon particles
No full textWe present two distinct implementations of the time resolved fluorescence polarization anisotropy (TRFPA) technique for the analysis of carbon nanoparticles collected from laminar laboratory flames and from the exhaust of a gasoline vehicle engine. By exploiting the high time-resolution and the spectral resolution of our TRFPA setups, we could identify two groups of particles, with diameter of 1.4 and 2.2 nm, respectively, within the laminar flame sample. On the other hand, the high time-resolution TRFPA analysis of the gasoline sample led to the identification of two distinct decay channels. The slower one was consistent with a single kind of small particle with diameter of 1.3 nm. Moreover, an analysis of the fast decay versus the temperature allowed us to rule out that it was due to the presence of lighter particles within the sample. Most likely, it is related to the relaxation of internal degrees of freedom
Optical and Spectroscopic Characterization of Rich Premixed Flames across the Soot Formation Threshold
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