Precipitation of dichloromethane as low-chlorine carbon nanoparticles from water by femtosecond laser pulses

Abstract We report on the transformation of dichloromethane to low-chlorine carbon nanoparticles by the exposure of aqueous dichloromethane solution and/or dichloromethane/water biphasic solution to femtosecond laser pulses. The pH of either solution immediately decreased due to the reduction of dichloromethane by hydrated electrons. The time evolution of transmittance revealed that particle formation was suppressed when the initial pH was low because protons scavenge hydrated electrons. The size and morphology of nanoparticles was independent of the initial pH and the reaction solution used. The analysis of the elemental composition of carbon particles showed that the Cl/C atomic ratio was, independent on the initial pH values, greatly reduced to 0.06. We propose that the violent destruction of dichloromethane and elimination of chlorine atoms not only as Cl − but also Cl 2 excludes chlorine atoms from the carbon network construction processes toward the formation of carbon nanoparticles.