Carbon spheres (CSs) were synthesized by chemical vapor deposition in Ar atmosphere using acetylene as carbon source. Vinyl-functionalized CSs was prepared by nitric acid oxidation and reacting with allylamine. The morphology, structure and effect of functionalization of CSs at different processing steps were characterized using field-emission scanning electron microscopy, Fourier-transform IR spectra, X-ray photoelectron spectroscopic and thermogravimetric analysis. The results show that some oxygen-containing groups such as carboxyl and hydroxyl were produced on the surface of CSs by nitric acid treatment, and vinyl groups were introduced on the surface of CSs by allylamine treatment. Acid-treated CSs are well dispersed in water and allylamine-treated CSs are well dispersed in organic solvent, which is preconditions of reactivity of CSs in liquid phase and lays the basis for the application of CSs. (C) 2011 Elsevier B. V. All rights reserved.