Direct Formation of SiO2 Nanohole Arrays via Iron Nanoparticle-Induced Carbothermal Reduction

Abstract

Hexagonally patterned SiO2 nanohole arrays having sub-10 nm of width were directly formed via carbothermal reduction of SiO2 with carbon-dissolved iron nanoparticles (NPs) (C(on iron NPs, s) + SiO2(s) <-> SiO(g) + CO(g)). Iron NPs prepared by hydroxylamine-mediated synthesis method resulted in not only nanoholes but also nanotrenches because the diameter of these iron NPs is suitable for the growth of single-walled carbon nanotubes (SWNTs) that further react with underneath SiO2 to produce nanotrenches. Higher yields of nanoholes were obtained by using larger-sized iron NPs (diameter: 3-8 nm) prepared from ferritins and by reducing the amount of active carbon precursor sources during the reaction, by which the growth of SWNTs were substantially suppressed. SiO2 nanohole arrays were then obtained from hexagonally self-arrayed iron NPs, which were fabricated using polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) micelles. In addition to the reactivity of carbothermal reduction, interparticular distance of the patterned iron NPs turned out to be a key factor to successfully form nanohole arrays. The interparticular distance was controlled by changing the composition of PS-b-P2VP micelles.