Laser-initiated chemical reactions in carbon suspensions

We report on laser-initiated chemical reactions in colloidal carbon suspensions. Irradiation of carbon particles ranging in size from 13 to 75 nm in diameter suspended in water, toluene, and benzene with high power nanosecond, picosecond, and feratosecond laser pulses leads to the formation of a number of gaseous hydrocarbons as well as a series of liquid-phase products. In the product gas above irradiated carbon suspensions in water, H-2 and CO, the main reaction products of the carbon-steam reaction, and numerous hydrocarbons ranging from C-1-C-4 were detected. Irradiation of particulate carbon in toluene and benzene gave H-2 as the main gas product with small amounts Of C-1-C-3 hydrocarbons. Bibenzyl and biphenyl were found as the main liquid products produced in toluene and benzene suspensions, respectively, but with numerous polycyclic aromatic hydrocarbons in smaller concentrations. The amount of products generated by pulsed laser irradiation is shown to depend on particle size and concentration, as well as the laser fluence and pulse width. The chemical reactions reported take place under conditions characterized by extremely high temperatures and pressures of short duration.