Reversible electron charge transfer in single-wall carbon nanotubes

Abstract

Single-wall carbon nanotubes (SWCNT) have proved to be very special materials due to their unique electronic properties. Over the last years many scientists have dedicated their research to the study of the these materials as an electronic system. Amphoteric doping effects (n-type and p-type), which can be reversed, became a very popular way of manipulating the optic and electronic properties of carbon nanotubes. In the particular case of SWCNT, the most common and widely used procedure, which changes their properties, is acid treatment applied as a purification procedure. The effect of the addition of this kind of the dopant has been widely studied but not fully understood so far. Here, we present a study, of two kinds of SWCNT, produced within different techniques: (i) chemical vapors deposition and (ii) laser ablation. The main difference between the two types is the diameter distribution of the obtained materials, which is broad in the first technique and narrow in the second. After the acid treatment it is possible to observe a diameter sensitive doping effect on both samples. Resonance Raman spectroscopy, optical absorption spectroscopy (OAS) in UV/Vis/NIR and the Fourier transform middle-infrared (FTIR) spectroscopy have been applied for the characterization of the samples.

Thermal and structural stability of single- and multi-walled carbon nanotubes up to 1800°C in Argon studied by Raman spectroscopy and transmission electron microscopy

“…The D-band center and width of present SWCNT specimens (Table 4) matched closely with literature data obtained from different SWCNTs using similar laser energy [24,25]. Since, D-band position significantly depends on laser excitation energy and shifts at a rate between 43 cm À1 /eV and 53 cm À1 /eV [11,26] thus, D-band location can vary between 1273 cm À1 and 1350 cm À1 depending on laser energy used [11,15,17,18,[24][25][26][27][28][29][30]. Further, the D-band center in CNT is usually lower than that observed in bulk sp 2 graphite and depends on tube diameter as v D-band 1 (1/d) [21].…”

“…The next Raman active peak obtained from the specimens was the disorder-induced D-band associated with vibrations of carbon atoms having dangling bonds in plane terminations of disordered graphite indicating the level of defects in CNT [18][19][20][21][22][23]. The D-band center and width of present SWCNT specimens (Table 4) matched closely with literature data obtained from different SWCNTs using similar laser energy [24,25]. Since, D-band position significantly depends on laser excitation energy and shifts at a rate between 43 cm À1 /eV and 53 cm À1 /eV [11,26] thus, D-band location can vary between 1273 cm À1 and 1350 cm À1 depending on laser energy used [11,15,17,18,[24][25][26][27][28][29][30].…”

Raman Study on Doped Multiwalled Carbon Nanotubes

“…The guest molecule can either intercalate the walls [16], or react with the defects in the surface creating attached functional groups [5]. It is known that both cases lead to an increase of the amount of defects in the CNT [17]. The D band indicates the defects in the graphitic structure and the G/D intensity ratio presents the relative sample purity.…”

Restriction of Phase Transformation in Carbon Nanotube-Reinforced Yttria-Stabilized Zirconia

“…The ratio of the peak intensities of the two bands indicates the quality of the C-C bond (i.e., similar intensities of both the bands indicate high degree of structural defects). [53] In SPSed pellets of the composites, the wave number of D-band as well as the I D /I G ratio increase when compared to that of the powdered samples owing to the changes in the structure of the MWNTs that occur during sintering. Such change in Raman spectra is reported by Bokobza et al due to heating effect induced by laser power.…”