SWCNT dispersions diluted

The same Carbolex and HiPCO SWCNT dispersions as those previously studied in Section 3.1.2 were examined with UV-Vis spectroscopy. Samples were taken regularly during the sonicating process, diluted and UV-Vis spectra were recorded. Since desorption processes are typically quite slow, it was assumed that the amount of SDS molecules adsorbed on the CNT walls was not significantly influenced by dilution, and UV-Vis spectra were typically immediately recorded after dilution. " Please note that the dilution factor — in other words, the CNT concentration after dilution [i.e., 6.7 x 10 wt% for the standard SWCNT dispersions) — was chosen in such a way that all the UV-Vis absorbance values remained below 1 so that the error inherently present in the measurement itself is reduced. At this dilution, the contribution of scattering can be ignored. " ... 

A 200-fold excess of freshly prepared and filtered (Celite) solution of the nucleophilic carbene dipyridylimidazolidene was added to a dispersion of SWCNTs in THF at -60 °C. After stirring at -60 °C for 3 h, the reaction mixture was slowly warmed to room temperature and then diluted with ethanol. The precipitated functionalized nanotubes were isolated by centrifugation and washed with ethanol [148],... 

Davis et al. [89] reported an important work regarding the immobilization of metalloproteins and enzymes on oxidized, purified and vacuum-annealed SWCNTs in aqueous solution. AFM experiments showed that the immobilization is mainly physical, without need for covalent activation or electrostatic interaction. In fact, cytochrome c at pHs below the isoelectric point and ferritin at pHs above the isoelectric point showed an important adsorption obtained just by stirring the nanotubes dispersion (0.03 mg/mL) in dilute protein solutions (50-100 pg/mL) for a given time (2-20 h). GOx could be also adsorbed in a very efficient... 

The SWCNTs were dispersed in DMF at a concentration of 0.5 g L by bath sonication for 40 min at 40—50 °C. In a typical procedure, 20 mL of this dispersion was filtered and washed on the filter with 10 mL of methanol and 10 mL of water. The solid was transferred into 20 mL of 8 M HNO3 in a glass vial, and the mixture was sonicated in a bath at 40—50 °C for a time ranging firom 30 min to 5 h. The mixture was diluted 1 2 with deionized water and filtered using a 0.45 pm PTFE filter. The solid was washed on the filter with water until the filtrate was neutral, washed with 10 mL of methanol, washed with 10 mL of DMF, and redispersed in 20 mL of DMF by bath sonication for 60 min. The filtrates from CoMoCat and HiPco nanotubes were colorless, but the filtrate from PLV nanotubes was Hght gray. AFM analysis of the PLV filtrate indicated the presence of nanotubes (Tchoul et al., 2007). 

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