Ying Wen

Synthesis of vertically aligned carbon nanotubes on metal deposited quartz plates

Without plasma aid, we have successfully synthesized vertically aligned carbon nanotubes (CNTs) on iron-, cobalt- or nickel-deposited quartz plates by chemical vapor deposition with ethylenediamine as a precursor. The amine serves as both etching reagent for the formation of metal nanoparticles and carbon source for the growth of aligned carbon nanotubes. The carbon nanotubes were vertically aligned in high density on a large area of the plain silica substrates. The density and diameter of CNTs is determined by the thickness of the deposited metal film and the length of the tubes can be controlled by varying the reaction time. High-resolution transmission electron microscopy analysis reveals that the synthesized CNTs are multiwalled with a bamboo-like structure. Energy dispersive X-ray spectra demonstrate that the CNTs are formed as tip growths. Raman spectrum provides definite evidence that the prepared CNTs are multiwalled graphitic structure.

Synthesis of vertically aligned carbon nanotubes films on silicon wafers by pyrolysis of ethylenediamine

Well-aligned carbon nanotubes (CNTs) have been grown on nickel-deposited silicon wafers by thermal chemical vapor deposition (CVD) of ethylenediamine precursor. The CNTs are vertically aligned at high density over large areas on the silicon surface. The size and the density of the nanotubes were found to be dependent on the thickness of the Ni film. The length of the nanotube array can be controlled by varying the CVD time. High-resolution transmission electron microscopy analysis revealed that the CNTs present bamboo-like multi-walled structure.

Electrochemical functionalization of vertically aligned carbon nanotube arrays with molybdenum oxides for the development of a surface-charge-controlled sensor

The modification of inorganic polymeric oxides at the surface of carbon nanotubes is of paramount importance for developing new sensors. In this study, molybdenum oxide (MoOx) film was electrodeposited on the surface of multi-walled carbon nanotubes (MWNTs) by cycling the potential between +0.20 and ?0.80?V (versus 3?M KCl?Ag|AgCl) in Na2MoO4 solution. The MoOx-modified nanotube (MoOx/MWNT) electrode displays well-defined redox transitions in 5?mM H2SO4 or in phosphate buffer solution (PBS), which can be attributed to the reductive formation and the re-oxidation of hydrogen molybdenum oxides. X-ray photoelectron spectra (XPS) showed that the deposited MoOx films are mainly Mo6+ complexes. Both MWNT and MoOx/MWNT electrodes have ideal reversibility in 5?mM K3[Fe(CN)6] in 1?M KCl as supporting electrolytes at all sweep rates (0.02?1.00?V?s?1) by cyclic voltammetry. The negatively charged surface of MoOx/MWNTs can further attract molecular cations such as Ru(NH3)63+. The MoOx/MWNT electrode exhibited electrocatalytic ability towards the reduction of bromate due to high surface area and the fast electron transfer rate of nanotubes. Thus, electrochemical modification of inorganic polymeric oxides on the carbon nanotube provides a simple method for the preparation of novel sensors.