Optical properties of gas-evaporated carbon nanoparticles

Extinction and Raman spectra of gas-evaporated carbon nanoparticles were studied. It was found from Raman spectroscopy that the gas-evaporated carbon nanoparticles consist of small sp2 carbon clusters and the sp2 clusters grow on thermal annealing without affecting the size of the particle itself. The as-deposited samples show an extinction peak at about 230 nm, which exhibits a red shift as the annealing temperature increases. Combining the results of Raman spectroscopy, we conclude that the extinction peak arises from the π-plasmon resonances in sp2 clusters and the resonant frequency decreases as the sp2 clusters grow.