CNT films

Filtering the tube suspension through a 0.2 xm pore ceramic paper leaves a uniform black deposit on the paper and can produce aligned CNT films [30]. The deposited material was transferred on a thin Teflon sheet by pressing the tube-coated side of the filter on the plastic and then the filter was lifted off to expose the surface. Scanning electron microscopic study reveals that the tubes are highly aligned perpendicular to the Teflon surface [30]. 

We have determined the optical properties as a function of temperature by measuring the reflectivity / (co) of the oriented CNT films from the far infrared (FIR) up to the ultra-violet (UV) (i.e., from 20 cm" up to 3x10 cm" ), using three spectrometers with overlapping frequency ranges [12, 13],... 

Fig. 3. Reflectivity (a) and optical conductivity spectra (b) of oriented CNTs films along the an and aj directions. Bruggeman (BM) and Maxwell-Garnett (MG) fits (see text and Table 2) are also presented.

Fig. 5. Schematic representation of the measured CNT films. The effective medium is the result of tubes dispersed in an insulating host (glassy graphite).

The formation mechanism is illustrated in Fig. 5. CNT film has also been found to grow epitaxially on the surface of a (3-SiC crystal particle [29], The present method should prove to be applicable to flat panel displays or to electronic devices utilising MWCNTs,... 

Field emission applicable to flat-panel display is one of the most advanced and energetically studied applications of CNTs. The apparatus is illustrated in Fig. 12 along with pictures of closed-tips of MWCNTs. In spite of their high workfunction (4..3 eV for MWCNTs [39]), CNTs emit electrons from their tips when high voltages (100-1000 V) are applied between the metal grid of the accelerator and the CNT film which are separated by 20 im [38]. 

Fig. 12. (a) Schematic illustration of the setup for field emission experiment using a CNT film, (b) TEM picture of a tip of an MWCNT where electrons are emitted, (c) Illustration of the electron emission by applied electric field [38]. 

CNT films are also of interest from morphological aspect because their structure provides nanoscale voids within the networks of CNTs. For example, composites with conducting polymers are very interesting both from scientific and technological interests, since we would expect CNTs to give a well-dispersed film. 

Fig. 16. Top Illustration of the macroscopic device. BCHA-PPV is poly(2,. i-bis(cholestanoxy)-1,4-phenylenevinylene) [3. il. Bottom Cross section of the device (a) Al contact, (b) polymer layer and (c) CNT film.

The lotus-like and honeycomb-like aligned CNT films with a combination of micro- and nanostructures were also reported (Sun et al., 2003 Choi et al., 2003). They all displayed super-hydrophobic properties as shown in Fig. 9.14. The well-aligned CNT-polymer films or coatings have potential on applications such as super-hydrophobic surfaces to textiles, coatings, gene delivery, micro-fluid channels, non-wetting liquid transfer, and so forth. 

Fig. 9.13 SEM images of aligned CNT films by pyrolysis of metal phthalocyanines (a) top view and (b) cross-sectional view (Kam et al., 2005. With permission from all authors and Wiley)...

I. Armentano, M. Dottori, D. Puglia, ).M. Kenny, Effects of carbon nanotubes (CNTs) on the processing and in-vitro degradation of poly(DL-lactide-co-glycolide)/CNT films, Journal of Materials Science-Materials in Medicine, vol. 19, pp. 2377-2387, 2008. 

Figure 3.14. CNT/polymer nanocomposites observed in SEM (a) and (b) P(S-ABu)/MW CNT films surface respectively prepared by evaporation and film formation or freeze-drying and hot-pressing but showing similar fillers distribution (c) and (d) PS matrix containing ungrafted or PS-grafted N-doped CNT a fracture performed at ambient temperature highlights the difference in fillers/matrix interface strength. Scale bars 1 pm.

Figure 2, AFM im es of logic gate on FET based on CNT film and carbon nanowire resistor a - general view, b - CNT film on carbon electrode c -nanowire in carbon electrode.

An amperometric biosensor for OPC pesticides based on a CNT-modified transducer and an OPH biocatalyst is described. A bilayer approach with the OPH layer on top of the CNT film was used for preparing the CNT/OPH biosensor. The CNT layer leads to a greatly improved anodic detection of the enzymatically generated p-nitrophenol product, including higher sensitivity and stability. The sensor performance was optimized with respect to the surface modification and operating conditions. Under the optimal conditions the biosensor was used to measure as low as... 

Similarly, perturbations such as those described above have also been reported in the case of PANI covalently functionalized SWNT samples prepared by electrochemical polymerization of aniline on a CNT film deposited on a Pt electrode. The covalent functionalization of SWNTs with PANI was explained, on the basis of the Raman and FTIR spectra shown in Figures 5.10 and 5.11, respectively, as taking place in two successive steps [26]. The first corresponds to the electrochemical polymerization of aniline on a SWNT film from which one obtains a composite of PANI-leucoemeraldine salt (LS)-functionalized... 

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