| Autor: |
Brotherton EE; Dainton Building, Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K., Chan DHH; Dainton Building, Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K., Armes SP; Dainton Building, Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K., Janani R; Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, South Yorkshire S1 1WB, U.K., Sammon C; Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, South Yorkshire S1 1WB, U.K., Wills JL; School of Physics and Astronomy, University of Kent, Canterbury, Kent CT2 7NH, U.K., Tandy JD; School of Chemistry and Forensic Science, University of Kent, Canterbury CT2 7NZ, U.K., Burchell MJ; School of Physics and Astronomy, University of Kent, Canterbury, Kent CT2 7NH, U.K., Wozniakiewicz PJ; School of Physics and Astronomy, University of Kent, Canterbury, Kent CT2 7NH, U.K., Alesbrook LS; School of Physics and Astronomy, University of Kent, Canterbury, Kent CT2 7NH, U.K., Tabata M; Department of Physics, Chiba University, Chiba 2638522, Japan. |
| Abstrakt: |
Polycyclic aromatic hydrocarbons (PAHs) are found throughout the interstellar medium and are important markers for the evolution of galaxies and both star and planet formation. They are also widely regarded as a major source of carbon, which has implications in the search for extraterrestrial life. Herein we construct a melting point phase diagram for a series of phenanthrene/pyrene binary mixtures to identify the eutectic composition (75 mol % phenanthrene) and its melting point (83 °C). The molten oil obtained on heating this eutectic composition to 90 °C in aqueous solution is homogenized in the presence of a water-soluble polymeric emulsifier. On cooling to 20 °C, polydisperse spherical phenanthrene/pyrene hybrid microparticles are obtained. Varying the stirring rate and emulsifier type enables the mean microparticle diameter to be adjusted from 11 to 279 μm. Importantly, the phenanthrene content of individual microparticles remains constant during processing, as expected for the eutectic composition. These new hybrid microparticles form impact craters and undergo partial fragmentation when fired into a metal target at 1 km s -1 using a light gas gun. When fired into an aerogel target at the same speed, microparticles are located at the ends of characteristic "carrot tracks". Autofluorescence is observed in both types of experiments, which at first sight suggests minimal degradation. However, Raman microscopy analysis of the aerogel-captured microparticles indicates prominent pyrene signals but no trace of the more volatile phenanthrene component. Such differential ablation during aerogel capture is expected to inform the in situ analysis of PAH-rich cosmic dust in future space missions. |
