Analysis of the mechanism of the critical transition in irradiated acetylene that leads to generation of shell-shaped carbon nanoparticles

We have recently reported that onion-like shell-shaped carbon nanoparticles of high crystallinity could be generated through critical transition in the acetylene flow irradiated by a cw infrared CO2 laser [Choi et al. Advanced Materials 2004;16:1721–25]. This transition appeared as the temperature jump above a threshold value of the laser irradiance. The present paper explains the origin of this recent discovery. The heat balance on the surface of the growing particle is shown to allow the existence of two stable particle temperatures. Then, the temperature jump observed in our recent study is a transition from the low temperature regime to the high temperature regime. Implications of the finding for the processes of the carbon nanoparticle formation from hydrocarbons are also discussed.