Resonant excitation of precursor molecules in improving the particle crystallinity, growth rate and optical limiting performance of carbon nano-onions

A catalyst-free and highly efficient synthetic method for growing carbon nano-onions (CNOs) in open air has been developed through the laser resonant excitation of a precursor molecule, ethylene, in a combustion process. Highly concentric CNO particles with improved crystallinity were obtained at a laser wavelength of 10.532νm through the resonant excitation of the CH₂ wagging mode of the ethylene molecules. A higher growth rate up to 2.1gh ^{- 1} was obtained, compared with that without a laser (1.3gh ^{- 1}). Formation of the CNOs with ordered graphitic shells is ascribed to the decomposition of polycyclic aromatic hydrocarbons (PAHs) into C ₂ species. The optical limiting performances of the CNOs grown by the combustion processes were investigated. CNOs grown at 10.532νm laser excitation demonstrated improved optical limiting properties due to the improved crystallinity.