Abstract
Growth of amorphous carbon nanocoil (CNC) from acetylene on Si substrates was achieved by using nanosized Ag and K as the catalysts. The deposition of CNC was carried out inside a hot-wall reactor at 723 K using H 2 as the carrier gas. Based on the observed results, we propose a cooperative bimetal catalyst enhanced vapor - liquid - solid (VLS) growth mechanism to rationalize the CNC growth. In the reaction, the liquid phase metallic K dehydrogenated acetylene into the solid-state carbon, while the Ag nanoparticle assisted the extension of carbon one-dimensionally (1-D) via a tip-growth mechanism. Due to the adhesive force between the K liquid and the carbon, the 1-D solid curled along the C - K interface into the nanocoil shape. Some CNC samples were further heat-treated at 1423 K and showed very good field emission properties. They emitted electrons (10 μA/cm 2 ) at a turn-on field E to of 2.51 V/μm, while J max reached 17.71 mA/cm 2 at 5.64 V/μm. The field enhancement factor β was calculated to be 2124, comparable to other carbon nanotube (CNT) and CNC based emitters. The CNC was also characterized by using the electrochemical behavior of K 3 [Fe(CN) 6 ] via cyclic voltammetry (CV). The electrochemical surface area of a CNC electrode (geometric surface area 0.078 cm 2 ) was calculated to be 0.143 cm 2 . These properties suggest that the CNC electrodes may have potential applications in field emission and electrochemical devices. © 2010 American Chemical Society.