Carbon nanotubes molecules

Agapito LA, Bautista EJ, Seminario JM (2007) Conductance model of gold-molecule-silicon and carbon nanotube-molecule-silicon junctions. Phys Rev B 76 115316... 

Carbon Nanotubes Molecules made up of carbon atoms arranged in hexagonal patterns on the surface of cylinders. 

Single-walled carbon nanotubes Molecules composed solely of carbon which are cylindrical in cross section. See also fullerene. 

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970 s through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of 10 nm diameter [11, 12]. However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima s observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1], The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The lijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un-... 

The diameter distribution of single-wall carbon nanotubes is of great interest for both theoretical and experimental reasons, since theoretical studies indicate that the physical properties of carbon nanotubes are strongly dependent on the nanotube diameter. Early results for the diameter distribution of Fe-catalyzed single-wall nanotubes (Fig. 15) show a diameter range between 0.7 nm and 1.6 nm, with the largest peak in the distribution at 1.05 nm, and with a smaller peak at 0.85 nm [154]. The smallest reported diameter for a single-wall carbon nanotube is 0.7 nm [154], the same as the diameter of the Ceo molecule (0.71 nm) [162]. 

In general, nanotechnology MBBs are distinguished for their unique properties. They include, for example, graphite, fullerene molecules made of various numbers of carbon atoms (C60, C70, C76, C240, etc.), carbon nanotubes, nanowires, nanocrystals, amino acids, and diamondoids [97]. All these molecular building blocks are candidates for various applications in nanotechnology. 

Figure 17.4 Cartoon representation of strategies for studying and exploiting enzymes on electrodes that have been used in electrocatalysis for fuel cells, (a) Attachment or physisorption of an enzyme on an electrode such that redox centers in the protein are in direct electronic contact with the surface, (b) Specific attachment of an enzyme to an electrode modified with a substrate, cofactor, or analog that contacts the protein close to a redox center. Examples include attachment of the modifier via a conductive linker, (c) Entrapment of an enzyme within a polymer containing redox mediator molecules that transfer electrons to/from centers in the protein, (d) Attachment of an enzyme onto carbon nanotubes prepared on an electrode, giving a large surface area conducting network with direct electron transfer to each enzyme molecule.

Dong, L.F. etal. (2009) Cytotoxicity effects of different surfactant molecules conjugated to carbon nanotubes on human astrocytoma cells. Nanoscale Research Letters, 4 (12), 1517-1523. 

A new approach to improve the performance of solar devices using natural pigments is to employ carbon nanotube (CNT)-based counter-electrodes. As previously reported, the excited dye transfers an electron to Ti02 and so it acquires a positive charge. Then, the cationic molecule subtracts an electron from the counterelectrode which is transported by the electrolyte. This reaction is usually catalyzed by means of conductive and electrocatalytically active species for triiodide reduction of carbon coatings. CNTs have a high superficial area, which represents a very... 

The aluminum is incorporated in a tetrahedral way into the mesoporous structure, given place to Bronsted acidic sites which are corroborated by FTIR using pyridine as probe molecule. The presence of aluminum reduces the quantity of amorphous carbon produced in the synthesis of carbon nanotubes which does not happen for mesoporous silica impregnated only with iron. It was observed a decrease in thermal stability of MWCNTs due to the presence of more metal particles which help to their earlier oxidation process. 

Figure 8.18 TbPc2-based molecular spin-tronic devices, (a) Graphene nanotransistor with sensitivity at the single-molecule level [39, 256], (b) Scheme of the supramolecular spin valve architecture [217]. (c) Scheme of the carbon nanotube NEMS. The magnetization reversal of a TbPc 2 SIMM from a spin state Jz = +6 to Jz = -6 results in a rotation...

G. Pastorin, K. Kostarelos, M. Prato, and A. Bianco, Functionalized carbon nanotubes Towards the delivery of therapeutic molecules, /. Biomed. Nano-technol., 1 (2005) 133-142. 

The orbital bonding nature within carbon nanotubes creates unique electrical properties within a non-metallic molecule, which is a result of the delocalization of the -electron donated by each atom. Electrical conductivity can take place along the entire nanotube due to the freedom of -electron flow, making possible the design of circuits of extremely low nanometer diameter. 

Some of the better solvents for pure SWNTs are the amide-containing ones, like DMF or N-methylpyrrolidone, but they still do not permit full dissolution, just dispersion (Boul et al., 1999 Liu et al., 1999). The addition of surfactants to carbon nanotube suspensions can aid in their solubilization, and even permit their complete dispersion in aqueous solution. The hydro-phobic tails of surfactant molecules adsorb onto the surface of the carbon nanotube, while the hydrophilic parts permit interaction with the surrounding polar solvent medium. 

Figure 15.12 Detergent molecules can be used to solubilize carbon nanotubes by adsorption onto the surface through hydrophobic interactions and create half-micelle structures with the hydrophilic head groups facing outward into the aqueous environment.

Figure 15.13 Tween 20 can be activated with CDI using its hydroxyl groups to create an amine-reactive imidazole carbamate intermediate that then can be used to coat a carbon nanotube. The result is an activated nanotube that can be used to couple proteins and other amine-containing molecules.

Figure 15.14 The NHS ester of a pyrene butyric acid derivative can be used to modify a carbon nanotube by adsorption of its rings onto the surface of the tube. The NHS ester groups then can be used to couple amine-containing molecules to form amide bonds.

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. 

The covalent methods previously discussed for fullerene modification using cycloaddition reactions also can be applied to carbon nanotubes. This strategy results in chemically linking molecules to the graphene rings on the outer surface of the cylinder, resulting in stable... 

K. Besteman, J.O. Lee, F.G.M. Wiertz, H.A. Heering, and C. Dekker, Enzyme-coated carbon nanotubes as single-molecule biosensors. Nano Lett. 3, 727-730 (2003). 

Improving the electroanalytical sensitivity and selectivity for small biological and pharmic molecules with carbon nanotubes... 

Y.D. Zhao, W.D. Zhang, H. Chen, and Q.M. Luo, Direct electron transfer of glucose oxidase molecules adsorbed onto carbon nanotube powder microelectrode. Anal. Sci. 18, 939-941 (2002). 

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