Carbon nanotubes multiwall arrays

Yu, H. Quan, X. Chen, S. Zhao, H., Ti02-multiwalled carbon nanotube heterojunction arrays and their charge separation capability. J. Phys. Chem. C 2007, 111, 12987-12991. 

T.D. Wilkinson, X. Wang, K.B.K. Teo, W.I. Milne, Sparse multiwall carbon nanotube electrode arrays for liquid-crystal photonic devices. Adv. Mater. 20, 363-366 (2008)... 

Fig. 12.3 Fabrication of the nanocomposite paper units for battery, (a) Schematic of the battery assembled by using nanocomposite film units. The nanocomposite unit comprises LiPF6 electrolyte and multiwalled carbon nanotube (MWNT) embedded inside cellulose paper. A thin extra layer of cellulose covers the top of the MWNT array. Ti/Au thin film deposited on the exposed MWNT acts as a current collector. In the battery, a thin Li electrode film is added onto the nanocomposite, (b) Cross-sectional SEM image of the nanocomposite paper showing MWNT protruding from the cel-lulose-RTIL ([bmlm] [Cl]) thin films (scale bar, 2pm). The schematic displays the partial exposure of MWNT. A supercapacitor is prepared by putting two sheets of nanocomposite paper together at the cellulose exposed side and using the MWNTs on the external surfaces as electrodes, (c) Photographs of the nanocomposite units demonstrating mechanical flexibility. Flat sheet (top), partially rolled (middle), and completely rolled up inside a capillary (bottom) are shown (See Color Plates)...

Fig. 12.3 Fabrication of the nanocomposite paper units for battery, (a) Schematic of the battery assembled by using nanocomposite film units. The nanocomposite unit comprises LiPF6 electrolyte and multiwalled carbon nanotube (MWNT) embedded inside cellulose paper. A thin extra layer of cellulose covers the top of the MWNT array. Ti/Au thin film deposited on the exposed MWNT acts as a current collector. In the battery, a thin Li electrode film is added onto the nanocomposite.

An other interesting strategy is the modification of the surface of the electrodes with multiwalled carbon nanotubes (MWNTs) or single-walled carbon nanotubes (SWNTs) [13,32]. The MWNTs are grown on the electrodes covered with a nickel catalyst film by plasma-enhanced chemical vapour deposition and encapsulated in Si02 dielectrics with only the end exposed at the surface to form an inlaid nanoelectrode array [13]. In the other case, commercial SWNTs are deposited on SPE surface by evaporation [32], The carbon nanotubes are functionalised with ssDNA probes by covalent attachment. This kind of modification shows a very efficient hybridisation and, moreover, the carbon nanotubes improve the analytical signal. 

Figure 1.6. Carbon nanotube structures obtained by chemical vapor deposition synthesis, (a) SEM image of self-oriented MWNT arrays. Each tower-like structure is formed by many closely packed multiwalled nanotubes, (b) SEM top view of a hexagonal network of SWNTs (line-like structures) suspended on top of silicon posts (bright dots), (c) SEM top view of a square network of suspended SWNTs, (d) Side view of a suspended SWNT power line on silicon posts (bright) and (e) SWNTs suspended by silicon structures (bright regions). Reproduced from reference 3 with permission from American Chemical Society.

All known types of carbon nanotubes are potential field emitters (Figure 3.55b). Single and bundled SWNT as well as multiwalled species show this behavior. Individual tubes may be attached to a conductive support, but they might just as well be employed in the shape of ordered or unordered films or as structured arrays (Section 3.3.5). The respective products can be selected depending on the desired application. The choice of single- or multiwalled species influences emission properties, too SWNTs feature a low work function, whereas MWNTs better suit continuous use because they are clearly more stress resistant... 

Trace concentrations of triazines in drinking water may be determined by U.S. EPA Method 525.2, which involves a solid-phase extraction followed by GC/MS analysis. Alternatively, such substances may be detected by GC/NPD following liquid-liquid extraction (U.S. EPA Method 507). Pinto and Jardim (2000) have described a method to measure triazine residues in water. Their method involves concentrating the samples with C-18 solid-phase extraction cartridges followed by HPLC analysis using a C-18 column with UV detection at 230 nm. The method was applied to measure atrazine, simazine, cyanazine, and ametryne in water at a detection level of O.l/irg/L. Zhou et al. (2006) used multiwalled carbon nanotubes as the adsorbents for preconcentration of triazines in water followed by their measurement by HPLC with a diode-array detector. The method was used to analyze atrazine and simazine in environmental waters. The authors have reported detection limits of 33 and 9 ng/L, respectively, for these two compounds under their optimal conditions. 

Zhou, Q., J. Xiao, W. Wang, G. Liu, Q. Shi, and J. Wang. 2006. Determination of atrazine and simazine in environmental water samples using multiwalled carbon nanotubes as the adsorbents for preconcentration prior to high performance liquid chromatography with diode array detector. Talanta 68(4) 1309-15. 

Gas sensors based on field ionization from multiwall carbon nanotube arrays grown on PSi templates have been developed (Nikfaijam et al., 2010). Such sensors showed good sensitivity, selectivity and short response times, as well as higher discharge current and good mechanical stability in comparison with those which were fabricated on polished silicon substrates. Validation of the compatibility between PSi-based gas sensor technology and standard microelectronic processes has been demonstrated (Barillaro etal.,2010). 

H. Butt, Q. Dai, P. Farah, T. Butler, T.D. Wilkinson, J.J. Baumberg, G.A.J. Amaratunga, Metamaterial high pass filter based on periodic wire arrays of multiwalled carbon nanotubes. Appl. Phys. Lett. 97, 163102 (2010)... 

Jun L, Stevens R, Delzeit L, Hou Tee N, Cassell A, lie H, et al. Electronic properties of multiwalled carbon nanotubes in an embedded vertical array. Appl Phys Lett 2002 81 910-2. 

Wang X, Wilkinson TD, Mann M, Teo KBK, Milne WI. Characterization of a liquid crystal microlens array using multiwalled carbon nanotube electrodes. Appl Opt 2010 49 3311-5. 

Yun, Y.H., Shanov, V., Tu, Y., et al. Growth mechanism of long aligned multiwall carbon nanotube arrays by water-assisted chemical vapor deposition. J. Phys. Chem. B 1KK47),... 

Sheng LM, Liu P. et al., Effects of carbon-containing gases on the field-emission current of multiwalled carbon-nanotube arrays. Journal of Vacuum Science and Technology A, 2003. 21(4) 1202—1204. 

There are two main types of CNTs, i.e., single-waUed carbon nanotubes (SWCNT) consisting of a single sheet of graphene rolled seamlessly to form a cylinder and multiwalled carbon nanotubes (MWCNT) consisting of an array of such cylinders formed concentrically and separated by 0.35 nm. 

Cao, A., X. Zhang, C. Xu et al. 2001. Grapevine-Uke growth of single walled carbon nanotubes among vertically aligned multiwalled nanotube arrays. App/. Phys. Lett. 79 1252—1254. 

Some TEM micrographs of CNTs (a) multiwall carbon nanotubes and (b) multi-wall carbon nanotube arrays. (With permission from Cnano Company.)... 

Ago, H, Komatsu, T, Ohshima, S, Kuriki, Y and Yumura, Y (2000), Dispersion of metal nanoparticles for aligned multiwall carbon nanotube arrays , Appl Phys Lett 77,79-81. 

Aligned multiwall CNT arrays were synthesized as a basis for a microstructured catalyst, which was then tested in the Fischer-Tropsch reaction in a microchannel reactor [269]. Fabrication of such a structured catalyst first involved MOCVD of a thin but dense A1203 film on a FeCrAlY foam to enhance the adhesion between the catalyst and the metal substrate. Then, multiwall CNTs were deposited uniformly on the substrate by controlled catalytic decomposition of ethene. Coating the outer surfaces of the nanotube bundles with an active catalyst layer results in a unique hierarchical structure with small interstitial spaces between the carbon bundles. The microstructured catalyst was characterized by the excellent thermal conductivity inherent to CNTs, and heat could be efficiently removed from the catalytically active sites during the exothermic Fischer-Tropsch synthesis. 

In addition to SWNT, several other novel forms of carbon nanostructures have received much attention in recent years and hold great promise to find interesting and important applications among them, we can mention double- and multiwalled nanotubes, graphene ribbons, and nanohoms. At the same time, researchers have recently developed methods of producing nanotubes in a variety of arrangements. Due to the potentially different properties and applications of these arrangements (vertical forests, parallel arrays, yarns, ribbons, etc.) they are treated in separate sections. 

Fig. 12 (a, b) An 80 jjim carbon nanotobe island grown on a 100 xm conductive titanium nitride pad scale bar is 10 p.m [91]. These entwined nanotubes give a matted surface scale bar is 100 p.m. Reproduced with permission (c) Vertically aligned multiwalled carbon nanofiber array after elec-trodepositing a 40-nm-thick conformal polypyrrole film scale bar is 500 nm [92]. Reproduced with permission, (d) PEDOT nanotubes formed using PLLA templates [93]... 

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