Diameter controlled growth of single-walled carbon nanotubes from SiO2 nanoparticles

A rational approach is reported for the growth of single-walled carbon nanotubes (SWCNTs) with controlled diameters using SiO2 nanoparticles in a chemical vapor deposition system. The SiO2 nanoparticles with different sizes were prepared by thermal oxidation of 3-aminopropyltriethoxysilane (APTES) with different number of layers which were assembled on Si substrates. It was found that the size of SiO2 nanoparticles increased with the number of assembled APTES layers. Using these SiO2 nanoparticles as nucleation centers, the diameter distribution of as-grown SWCNTs were correlated with the size of SiO2 particles. In addition, both the classical longitudinal optical or transverse optical bands of SiC in in situ Raman spectra during the whole growth process and the Si 2p peak of SiC in the X-ray photoelectron spectra were not observed, suggesting that the carbon sources did not react with the SiO2 nanoparticles during the growth. Comparing to vapor-liquid-solid mechanism for metallic catalysts, vapor-solid mechanism is proposed which results in a lower growth rate when using SiO2 nanoparticles as nucleation centers. (C) 2011 Elsevier Ltd. All rights reserved.