Laser Ablation of Graphite in Water in a Range of Pressure from 1 to 146 atm Using Single and Double Pulse Techniques for the Production of Carbon Nanostructures

In the present work, laser ablation of a graphite target submerged in pure water was tested as a methodology for the production of carbon-based nanoparticles. The effect of varying the external pressure imposed to the liquid was investigated for the first time, in the range from 1 to 146 atm. Single or double laser pulses were used to ablate the target and the produced nanoparticles were characterized by atomic force microscopy (AFM) and by Raman spectroscopy. A spectroscopic study of the laser induced plasma features was carried out with a Ti target and interpreted in terms of laser-induced cavitation phenomena. Tubular nanoparticles of 25 nm average diameter were obtained only by single pulse (SP) ablation of graphite, while particles formed with the double pulse (DP) technique mainly consisted of graphite particulates. At 1 atm, these tubular nanoparticles were few and mixed with diamondlike carbon, while at 146 atm they were produced in a larger amount, suggesting that the high density effect induced by pressure plays a key role for their generation.