IR laser-induced ablation of Ag in dielectric breakdown of gaseous hydrocarbons: Simultaneous occurrence of metastable hcp and stable fcc Ag nanostructures in C:H shell

IR laser-irradiation of Ag in gaseous benzene or ethyne (1 T) results in ablation of Ag target and adjacent dielectric breakdown in gaseous hydrocarbons, the latter leading to dehydrogenation and carbonization reactions in the gas-phase and chemical vapor deposition on both substrate and target of Ag nanoparticles-containing carbonaceous films. The same irradiation of Ag in the hydrocarbons at 50 T induces only dielectric breakdown in the hydrocarbon and leads to gas-phase deposition of carbonaceous films. Volatile products of these processes were examined by FTIR spectroscopy and GC and GC/MS techniques and solid products were characterized by X-ray diffraction, FTIR, X-ray photoelectron and Raman spectroscopy and electron microscopy. These studies revealed co-existence of stable face-centered cubic and metastable hexagonal close-packed Ag-nanophases enveloped by a graphite-like shell and immersed in an amorphous hydrogenated carbon environment having both sp2- and sp3-hybridized structures. The nanosized Ag objects show stacking faults and undergo some oxidation in atmosphere to AgO and Ag3O4.