NANOPARTICLES PRODUCED BY LASER PYROLYSIS OF HYDROCARBONS - ANALOGY WITH CARBON COSMIC DUST

Infrared Laser Pyrolysis (IRLP) of gaseous molecules is a versatile me thod of synthesising a wide variety of nanopowders. The synthesis mech anism is based on condensation of heated gaseous precursors. This is t he same mechanism as postulated for carbon dust formation in the envel opes of evolved C-rich stars. An advantage of this technique, in contr ast with furnace-or plasma-heated gas phase techniques, is its well-de fined reaction zone and its infrared heating process. Using hydrocarbo n molecules C2H4 or C4H6 as precursors, a series of carbon-based nanop articles have been obtained in synthesis conditions corresponding to a variety of reaction temperatures. The nanoparticles were characterise d by Transmission Electron Microscopy (TEM) and infrared (IR) spectrom etry. Both IR spectrum and molecular organisation appear to depend on the synthesis conditions: the lower the reaction temperature, the stro nger the amorphous character and the more intense the IR bands. When p resent, IR bands are essentially due to aromatic CC and CH groups. Our experimental results are compared with results reported on other carb onaceous compounds and with astronomical observations.