Nano-TiO2 powders were successfully prepared by laser pyrolysis of TiCl4 (vapours). Alternatively, air and nitrous oxide were used as oxygen precursors. C2H4 was used as an energy transfer agent. The underlying phenomena for this photon-based molecular nanotechnology are discussed. For the present report, different titania nanosized powder batches were obtained by variation of the oxidizer nature and TiCl4 precursor flows. X-ray diffraction, transmission electron microscopy, electron energy loss spectroscopy, x-ray dispersive energy analysis, and IR and Raman spectrometry have been used to analyse the nanostructures and morphologies of the as-synthesized powders. Medium and high resolution TEM analyses indicate mean grain sizes between 12 and 28 nm. The different characterization techniques suggest that in the obtained anatase and rutile mixture the fraction of rutile phase depends on the nature of the oxygen precursor. At low TiCl4 flows, no chlorine contamination was detected in the reaction product. Further examination of the influence of other important system parameters will open new possibilities for titania preparation by the laser pyrolysis of TiCl4.

Carbon soot has been prepared by laser-induced pyrolysis of a mixture of ethylene (C 2 H 4 ) and benzene (C 6 H 6 ) vapor. The soluble part of the carbonaceous powder has been separated from its insoluble counterpart by soxhlet extraction in toluene. Several techniques were applied to obtain information on the composition of the extract. These included UV/visible and IR spectroscopy in solid and liquid phase, gas chromatography combined with mass spectrometry, gas-phase laser spectroscopy in a supersonic jet, and matrix spectroscopy in helium droplets, the latter being also combined with mass spectrometry. The analysis revealed that the carbonaceous powder contained various polycyclic aromatic hydrocarbons (PAHs). The highest concentration was found for the three-membered catacondensed PAHs, phenanthrene and anthracene. The results are discussed in view of the possible role of these molecules as interstellar dust components.

No abstract

No abstract

No abstract