Nanotubular

The similarity of M0S2 to graphite has been noted. Like elemental carbon, which has been found to form nanotubular stmctures, M0S2 has also been found to form nested stmctures upon exposure to the electron beam in an electron microscope (23). Moreover, M0S2 displays a variety of intercalation reactions typical of layered materials. Single-layer M0S2 has been successfully prepared and manipulated (22). 

Frackowiak E., Jurewicz K., Delpeux S., Beguin F. Nanotubular materials for supercapacitors. J Power Sourc 2001 97-98 822-5. 

Rustom, A., Saffrich, R., Markovic, I., Walther, P. and Gerdes, H.-H. Nanotubular highways for intercellular organelle transport. Science 303 1007-1010, 2004. 

Structural aspects of these nanoparticles are also discussed in this chapter. Extensive mathematical research has been devoted to polyhedramade of a single layer (13). Surprisingly, however, mathematical analysis of polyhedra and nanotubular structures made of two interconnected layers and more has started only very recently, as a result of the discovery of IF phases [see, e.g., (14)]. Most of the inorganic layered materials are comprised of more than one atomic layer, with strong chemical bonds interconnecting between the atoms of the different layers. Therefore a mathematical analysis of multilayer polyhedra is called for. 

A.L. Ivanovsky. Quantum chemistry in material science. Nanotubular forms of substance. Ekaterinburg, UrD RAS, 199,176 p. 

Enzymes can also be trapped within a nanotubular membrane by capping both faces of the membrane with a thin layer of porous polymer. In effect, arrays of enzyme-filled microcapsules are formed. Small molecules pass through the po-... 

FIG. 23. Charge discharge curves for nanotubular (a) and thin film (b) LiMn204/ polypyrrole electrodes. Current density = 0.1 mA cm. Electrolyte was 1 M LiC104 in 1 1 (vol.) propylene carbonate dimethoxyethane. 

It is easy to show [124] that the polypyrrole present in these electrodes contributes 8.85 X 10 mAh to the total experimental discharge capacity. Furthermore, it is known that over the potential window used here, LiMn204 has a theoretical (maximum) capacity of 148.3 mAh g [124]. Correcting the experimental capacities in Fig. 23 for the polypyrrole contribution and dividing by the mass of the LiMn204 used shows that in the nanotubular electrode 90% (133.8 mAh g ) of the theoretical capacity is utilized, whereas in the control electrode only 37% (54.9 mAh g ) of the capacity is used. These data clearly show that the nanotubular electrode is superior to the control LiMn204 electrode. 

It was noted above that a unique feature of the nanotubular electrode is the thin tubule walls, which ensure that the distance over which the Li must diffuse within the LiMn204 is small. If this factor is partially responsible for the improved performance of the nanotubular electrode (vs. the control electrode), then the performance should be further improved at higher current densities. This is because higher current densities force the charge... 

Finally, the other factor that could contribute to the improved performance of the nanotubule electrode is its higher surface area. This higher surface area would make the true current density at the nanotubular material lower than at the control material. In order to access the contribution of surface area, Brunauer-Emmett-Teller (BET) measurements were made on both the nanotubular and control electrodes [124], The specific surface areas were found to be 40 m g (nanotubule electrode) and 13 m g (control electrode). This factor of 3 increase in surface area cannot account for the factor of 12 improvement in capacity observed at the highest current... 

Raja KS, Mahajan VK, Misra M (2006) Determination of photoconversion efficiency of nanotubular titanium oxide... 

Fig. 5.33 Transmittance spectra of glass (Corning 2947) substrate, and 450°C aimealed nanotubular titania film atop same glass (Corning 2947) substrate.

Fig. 5.34 Refractive index variation of 450°C annealed nanotubular titania film, and for comparison a glass (Corning 2947) substrate, in the range 380 to lOSOnm. The Ti02 film has an average refractive index in the visible range of 1.66.

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