Mesoporous Silicas Impregnated with Cobalt and Nickel Oxide Nanoparticles and the Growth of Carbon Nanotubes There from

Metal oxide-based nanoparticles of cobalt or nickel were deposited inside the pores and on the surface of hexagonal mesoporous silicas by a direct synthesis technique using Pluronic P85 and P123 surfactants as structure directing agents with the appropriate metal phthalocyanine as a metal precursor. Metal loadings were between 0.4–3.2 wt.%. XPS studies showed that the initial form of the metal oxide nanoparticles were [CoO] and [NiO] respectively. Samples of these materials formed from the P85 surfactant and 3.0 wt.% were used to grow carbon nanotubes (CNTs) from acetylene feedstock in a catalytic chemical vapour deposition (CCVD) reactor at 800 °C. CNT growth appeared to be random and the CNTs had diameters ranging from <10 to >90 nm. Treatment of the metal impregnated silicas with nitric acid produced materials which, under the same CNT growth conditions, afforded more uniform CNTs with diameters between 5–15 nm. No significant loss in mesophase ordering was seen in the TEM, PXRD or nitrogen physisorption analysis of the acid washed samples. CNTs grown with cobalt impregnated silicas formed with the P123 surfactant had diameters in the range 15–25 nm. Raman spectroscopy of the CNT products showed the nanotubes were highly graphitised and of good quality.