Influence of molecular adsorption on the dielectric properties of a single wall nanotube: A model sensor

Abstract

Recent measurements of the resonance frequency of a copper disk covered with carbon nanotube bundles have shown characteristic resonance shifts during exposure with various gas molecules. The shifts were interpreted as the change of the dielectric permittivity of the system forming the sensor due to the electric properties of the adsorbed molecules. Starting from a simplified sensor model formed by one single wall nanotube, we develop a self-consistent approach to describe the variation of the linear dielectric susceptibility of the tube at the atomic scale when molecules are adsorbed at its external surface. The sensitivity of this model sensor is tested as a function of the apolar or polar nature of the admolecules, their adsorption geometry, their concentration, and the characteristics of the tube (length, diameter,...). The comparison with data on dielectric constant changes vs adsorption, coming from measurements of the resonance frequency shifts, displays striking agreement for most of the molecular species considered.

Electrical properties and reactivity under air–CO flows of composite systems based on ceria coated carbon nanotubes

“…2 represents the typical X-ray diffraction patterns obtained from the pure nanocrystalline ceria sample, and for the x = 15 wt.% composite sample. In full agreement with literature results [17][18][19]32], the two characteristic Bragg peaks of CNTs corresponding to the (0 0 2) and the (1 0 1) in the XRD pattern, are observed in this last sample close to the angle of 2 = 26.5 • . The ceria polycrystalline phase is clearly evidenced through the Bragg peaks of fluorite structure (JCPDS 89-8436): these diffraction peaks are systematically broadened, which confirms the nanostructuration of ceria phase.…”

“…7) is higher for the 15 wt.% sample. Our results can be compared with previous results obtained by gas chromatography (GC) [17][18][19][20]: the authors showed that the catalytic activity started from 50 • C (which corresponds to the beginning of the CO conversion). They observed that the complete CO conversion systematically occurred at 300 • C for all samples: in their work, the authors investigated nano-ceria, nanorods and individual nanotubes (without any DWNTs support).…”

“…This approach based on precipitation way is reported in previous works by several authors using carbon nanotubes (multi wall) [17][18][19][20] and anodic alumina membrane (AAM) [27] as template method. In our work, DWNTs are used as support for ceria nanoparticles.…”

“…CNTs based materials have attracted many technological and scientific interests: due to their remarkable properties linked to their tubular form and their nanoscale [11,12], they could offer exciting possibilities for a lot of applications including miniaturized and faster electronic devices. Carbon nanotubes seem also to be ideal for adsorption [13][14][15][16], sieving [17] and gas detection [18][19][20][21], due to their high specific surface and porosity. Chemical functionalization of carbon nanotubes would allow enhancing their electrical conductivity and generating new properties.…”

Fermi-Energy-Dependent Structural Deformation of Chiral Single-Wall Carbon Nanotubes

“…The calculations are performed for different values of ϵ in order to simulate a static screening due to the intrinsic permittivity of the nanotube and the environmental influence. The intrinsic dielectric constant ϵ NT for nanotubes and for graphene is approximately 4ϵ 0 (with ϵ 0 being the vacuum permittivity) [29]. For this reason, in the following analysis, we focus on what happens for ϵ ¼ 4ϵ 0 .…”