Direct SWNTs

The formation of SWNT/MEHPPV composites was confirmed by absorption and fluorescence spectra. The DMF solution of SWNT/MEHPPV composites or the aqueous solution of the shortened SWNTs was then dropped onto a mica or glass plate. The magnetic processing of the composites or the SWNTs was carried out by using a superconducting magnet (8T) in the horizontal direction, as described below. 

Figure 15.2 Polarized absorption spectra of SWNT/MEHPPV composites on glass plates in (a) the absence (OT) and (b) the presence of magnetic processing (8T). In the absence of magnetic processing (OT), the polarization direction of the light against the longitudinal direction of the glass plates is horizontal...

In the case of the vertical direction of magnetic field, after drying at ambient temperature under the magnetic field at the three positions (top, middle, and bottom) and in the absence of a magnetic field (outside the bore tube) as the control, the AFM images of the SWNTs on the mica were measured (Figure 15.3). 

Figure 15.3 AFM images of SWNTs on mica placed at the top ((a) and (b)), the middle (c), and the bottom (d) positions using magnet apparatus (vertical direction of magnetic field) and outside position (e) of the bore tube (OT).

The appearance of oxidation peaks in the CV is a direct evidence of PF f and BF 7 anions incorporation within the SWNT structure. The macromolecule Cn should then bear a positive charge as a result of subsequent oxidation following. In the case of PF 7 the anodic oxidation is ... 

Maehashi et al. (2007) used pyrene adsorption to make carbon nanotubes labeled with DNA aptamers and incorporated them into a field effect transistor constructed to produce a label-free biosensor. The biosensor could measure the concentration of IgE in samples down to 250 pM, as the antibody molecules bound to the aptamers on the nanotubes. Felekis and Tagmatarchis (2005) used a positively charged pyrene compound to prepare water-soluble SWNTs and then electrostatically adsorb porphyrin rings to study electron transfer interactions. Pyrene derivatives also have been used successfully to add a chromophore to carbon nanotubes using covalent coupling to an oxidized SWNT (Alvaro et al., 2004). In this case, the pyrene ring structure was not used to adsorb directly to the nanotube surface, but a side-chain functional group was used to link it covalently to modified SWNTs. 

FTIR is also an effective way to assess the orientation or alignment of CNTs since the absorption is much stronger when the electric field of the incident light wave is parallel to the axis of aligned CNTs. The anisotropic feature has been found in SWNT-PAN composite [164], The infrared spectra of PAN fibers for the two polarization directions (parallel and perpendicular) are comparable, while the composite fibers show significant differences in the two polarization directions. 

CNT conductive surface modification Both SWNTs and MWNTs can be deposited directly from a CNT dispersion as a random network or thin film on conventional electrodes. From the point of view of their construction such electrodes are very easy to prepare but they may suffer from mechanical instability, thus limiting their application. 

Without doubt, the advent of carbon nanotubes has opened up iimovative perspectives for research and development of carbon electrodes. In this chapter, we have attempted to highlight the electrochemical properties of carbon nanotubes by rooting them mainly on their structural, electronic and chemical properties. If chirality of SWNTs could be controlled, it would be possible to probe electrochemically the unique electronic properties of the tubes with their corresponding unique DOS distribution and establish direct correlations between electronic structure and electrochemistry. However, so far, most of their electrochemical applications are based on ensembles of CNTs (MWNTs or SWNTs) in thin films supported on conductive surfaces or composites. Such ensembles, not so well defined from the structural point of view, contain a mixture of tubes with different diameters and DOS... 

In section IID, we introduced the utilization of chemical enhancement effect for higher sensitivity in TERS. Here, it should be pointed out that in addition to electromagnetic enhancement and chemical enhancement effects, physical deformation induced by tip-applied force showed extra enhancement effect in TERS on carbon materials such as SWNTs and fullerene molecules (Yano et al. 2005, 2006 Verma et al. 2006). This tip-pressurized effect is a unique feature of TERS and not observable in SERS. Since the spatial resolution of TERS with tip-pressurized effect is determined by the size of the very end of the metallic tip that has direct contact with the molecules, this is a very promising approach to improve the spatial resolution of the near-field microscope. 

The electronic properties of SWNTs depend on the direction in which the graphite sheet rolls up. Graphite itself is a 2-D metal, exhibiting metallic conductivity within the... 

These modification are indicative of a chemical mechanism in the SERS process in particular in very thin films for which chemical reactions are optimised. These experiments show in addition that metallic tubes are mainly involved, evidenced by the decrease of the Breit-Wigner-Fano component, as due to a possible direct interaction between nanotubes and C6o leading to the formation of SWNTs+C6o complexes [19]. 

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