1998A&A...330.1127H

Infrared Laser Pyrolysis (IRLP) of gaseous molecules is a versatile method of synthesising a wide variety of nanopowders. The synthesis mechanism is based on condensation of heated gaseous precursors. This is the same mechanism as postulated for carbon dust formation in the envelopes of evolved C-rich stars. An advantage of this technique, in contrast with furnace- or plasma-heated gas phase techniques, is its well-defined reaction zone and its infrared heating process. Using hydrocarbon molecules C₂H₄ or C₄H₆ as precursors, a series of carbon-based nanoparticles have been obtained in synthesis conditions corresponding to a variety of reaction temperatures. The nanoparticles were characterised by Transmission Electron Microscopy (TEM) and infrared (IR) spectrometry. Both IR spectrum and molecular organisation appear to depend on the synthesis conditions: the lower the reaction temperature, the stronger the amorphous character and the more intense the IR bands. When present, IR bands are essentially due to aromatic CC and CH groups. Our experimental results are compared with results reported on other carbonaceous compounds and with astronomical observations.