Graphitization of Chlorohydrocarbons in Laser-induced Plasma Filaments

Abstract

The decomposition of aqueous chlorohydrocarbons regarded as environmental pollutants has been widely studied. However, it is usually difficult to separate liquid and/or volatile products originated from chlorohydrocarbons from reactant solution. We succeeded to precipitate hydrophobic carbon nanoparticles and their agglomerates from aqueous dichloromethane by femtosecond laser (0.8 µm, 40 fs) irradiation. In the case of water/dichloromethane bilayer solution, the precipitates were produced in abundance when the water layer was exposed to femtosecond laser pulses. The time evolution of pH and transmittance revealed that the precipitation of carbon particles was preceded by dechlorination. Focusing intense femtosecond laser pulses onto water creates a high density of reactive species in a well-confined volume; i.e., plasma filament. The graphitization hence solidification by using laser pulses could be an useful way to remove chlorinated compounds from their aqueous solution.