Separations nanotube

Electron microscopy analyses of the separated fractions revealed no significant differences in their images from those of the pre-separated mixtures.Major differences were observed in their near-infrared (IR) absorption (Figure 6.5) and resonance Raman spectra, consistent with the metallic and semiconducting fractions.In Raman spectra (Figure 6.6), the G-band of the metallic fraction was much broader and more asymmetric, known as the Breit-Wigner-Fano (BWF) feature, as compared with those for the pre-separation nanotube sample and more so the semiconducting fraction. 

The superior conductivity of separated metallic SWNTs was also verified in the transparent conductive PEDOTiPSS composites. A suspension of the separated metallic SWNTs or the pre-separation nanotube mixture in DMSO was mixed with aqueous PEDOTiPSS for spray coating on to glass substrate. 

High power characteristics, more than 20 kW/kg at very high current densities to several hundreds of ampere per gram, were obtained in a number of works for EDLCs based on SWCNTs in sulfuric acid electrolyte. Such high power characteristics are explained by a regular structure of pores located between separate nanotubes and their sttands (see Fig. 27.23). The porous structure regularity means the practical absence of tortuous and corrugated pores and therefore the maximum conductivity of electrolyte in pores. 

Figure 23-10 Purification of carbon nanotubes by molecular exclusion chromatography. An electric arc struck between graphite rods creates nanometer-size carbon products, including tubes with extraordinary strength and possible use in electronic devices. Molecular exclusion chromatography separates nanotubes (fraction i) from other forms of carbon in fractions 2 and 3. The stationary phase is PLgel MIXED-A, a polystyrene-divinylbenzene resin with pore sizes corresponding to a molecular mass range of 2 000 to 40 000 000 Da. Images of carbon in each fraction were made by atomic force microscopy. [B. Zao, H. Hu, S. Niyogi, M. E. Itkis. M. A. Hamon, P. Bhowmik, M. S. Meier, and R. C. Haddon, . Am. Chem. Soc. 2001, i23,11673.]...

In the first institutimi of this laboratory module, an assessment of the overall deposition enviromnent of the nanotubes in association with catalyst particles was to be made. Therefore, no purification methods were used to separate nanotubes from catalyst particles. Although methods such as sonication in mineral acids for 15 min have been used to completely remove metal and support particles for MgO-supported nanotubes, this method is not so easily performed for alumina or silica... 

One of the new trends in chemical analysis appeared in the last decade is that the miniaturization. It becomes apparent in the miniaturization of analytical devices, separation procedures, measuring tools, analyzing samples and as a consequent the term micro have appeared. Further development of this trend have led to transfer from the term micro to nano one (nanoparticles, nanofluides, nanoprobes, nanoelectrodes, nanotubes, nanoscale, nanobarcode, nanoelectrospray, nanoreactors, etc). Thereupon a nanoscale films produced by Langmuir-Blodgett (LB) technique are proposed for modifying of chemical sensors. 

We next address selected Raman scattering data collected on nanotubes, both in our laboratory and elsewhere. The particular method of tubule synthesis may also produce other carbonceoiis matter that is both difficult to separate from the tubules and also exhibits potentially interfering spectral features. With this in mind, we first digress briefly to discuss synthesis and purification techniques used to prepare nanotube samples. 

Metal nanotube membranes with electrochemically suitable ion-transport selectivity, which can be reversibly switched between cation-permeable and anion-permselective states, have been reported. These membranes can be viewed as universal ion-exchange membranes. Gold nanotube molecular filtration membranes have been made for the separation of small molecules (< 400 Da) on the basis of molecular size, eg. separation of pyridine from quinine (Jirage and Martin, 1999). 

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