Polyyne synthesis and amorphous carbon nano-particle formation by femtosecond irradiation of benzene

A range of carbon nanoparticles together with polyyne chains are formed when liquid benzene is irradiated with 120fs pulses of intensity≈1×10¹⁴ Wcm⁻². The morphology and composition of these nanoparticles are reported. Atomic force microscopy (AFM) shows irradiation result in the formation of spherical, ellipsoidal and toroidal nanoparticles with sizes between 1 and 50nm. Surface enhanced Raman spectroscopy (SERS) indicates that the composition of these particles is primarily amorphous carbon reinforced by polyyne chains with 8–14 carbon atoms. Time of flight mass spectroscopy (TOF-MS) has been used to determine the precursor molecules created in the irradiation of benzene and shows the importance of ring-opening reactions in particle formation. A simple chemical mechanism is proposed to explain the appearance of polyyne chains in irradiated benzene.