Substitutional nitrogen incorporation through rf glow discharge treatment and subsequent oxygen uptake on vertically aligned carbon nanotubes

Abstract

By employing polarization-and temperature-dependent near-edge x-ray-absorption fine structure ͑NEXAFS͒ studies, we show that vertically aligned carbon nanotubes when subjected to low-pressure radio-frequency ͑rf͒ glow discharge can easily be doped with nitrogen atoms at predominantly graphitelike substitutional sites and at the same time preserve their vertical alignment in contrast to commonly used wet chemical functionalization methods. The O K edge NEXAFS spectra and angle-dependent x-ray phoelectron spectroscopy measurements established the presence of a significant amount of oxygen containing functional groups localized at the outer part of the walls. The amount of oxygen adsorbed on the carbon nanotubes is dependent on the introduction of nitrogen sites and exposed edge plane defects generated by plasma N treatment. Thermal gravimetric analysis measurements revealed a lower decomposition temperature for the plasma treated carbon nanotubes, which has its origin in the presence of a large fraction of active sites induced by rf glow discharge plasma treatment that accelerates the oxidation rate of N-doped carbon nanotubes. Our results indicate that rf low-pressure glowdischarge-mediated doping of nanotubes is a promising route to control the electronic structure of nanotubes and their reactivity due to introduction of active site defects.

Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

“…These results further substantiate that the rf-PECVD plasma treatment promotes the three dimensional sp 3 bonding configuration; whereas the ECR N-doping promotes the more desirable sp 2 bonding configuration 34,37,38 and further establishes that for field emission, the nitrogen bonding configuration in doped graphene is the dictating factor rather than the absolute nitrogen content.…”

“…A similar reduction in the structural order has been previously by Abbas et al in their study of the rf-PECVD N2 functionalised vertically aligned carbon nanotubes. 34 It should be mentioned that since the FLG are vertically aligned on a Si-substrate, it is expected that only the top-most surfaces of the FLG would be predominantly accessible to atomic nitrogen during the functionalization procedure. Fig.…”

“…A similar reduction in the structural order has been previously by Abbas et al in their study of the rf-PECVD N2 functionalised vertically aligned carbon nanotubes. 34 It should be mentioned that since the FLG are vertically aligned on a Si-substrate, it is expected that only the top-most surfaces of the FLG would be predominantly accessible to atomic nitrogen during the functionalization procedure. hybridised bonds, upwards movement of the Fermi level (discussed later) as well as the creation of defect sites in the FLG:N(ECR) samples are responsible for the enhancement of electron field emission current; whereas for the FLG:N(PECVD) samples, comparatively higher sp 3 bonding configuration is observed in the Raman analysis.…”

One-dimensional N2 gas inside single-walled carbon nanotubes

“…[4][5][6][7]17] Since encapsulated N 2 is not found for Et-SWCNT, the logical conclusion is that N 2 enters the SWCNT during synthesis using acetonitrile. In this case, the C-N species dissociates upon interaction with the catalyst particle.…”

“…The identification of N 2 (400.3 eV) is further backed up by the opposite bond orientation than observed for cyanic N (399.5 eV), that would in the same geometry be enhanced for ϕ = 0 • . [17] By taking into account the overall increase of signal, seen in the isotropic total edge jump of the C1s, the nematic order of the N 2 molecules is ξ = 0.22. This is comparable to ξ = 0.25 obtained from the C1s of the host 5%Ac-SWCNT.…”