Catalyst-free synthesis of onion-like carbon nanoparticles

A one-step process for the synthesis of onion-like carbon nanoparticles is described. The process is based on a thermolysis of a NaN3-C6Cl6 mixture. The effect of buffer gas (Ar or air) on the yield,morphology,and structure of the carbon products was investigated by electron microscopy,X-ray diffraction,and Raman spectroscopy. The products contained carbon-onions,amorphous carbon nanoparticles,and NaCl. The byproducts were completely removed using a simple purification process. The formation of onion-like nanoparticles is likely caused by a shock wave,a rapid increase of pressure,during thermolysis,which induced the coalescence of phenyl radicals.