Substantial progress are reported on field effect transistors (FET) consisting of semiconducting single wall carbon nanotubes (s-SWNTs) without detectable traces of metallic nanotubes and impurities. This outstanding result was made possible in particular by ultracentrifugation (250,000g) of solutions composed of SWNT powders with polyfluorene as extracting agent in toluene. Such s-SWNTs processable solutions were applied to realize FET, embodying randomly or preferentially oriented nanotube networks prepared by spin coating or dielectrophoresis. Devices exhibit a stable p-type semiconductor behavior in air with very promising characteristics: the on-off current ratio is 10 5 , the on-current level is around 10 µA and the estimated hole mobility is larger than 2 cm 2 /vs. The present results are demonstrated by optical absorption, Raman and electrical measurements.

A mild and efficient method for the functionalization of SWNTs by cycloaddition of azomethine ylides derived from trialkylamine-N-oxides is described. Selective reaction of semiconducting carbon nanotubes was achieved by preorganizing the starting N-oxides on the nanotube surface prior to generating the reactive ylides. Separation of met-SWNTs from functionalized sem-SWNTs was successfully accomplished by inducing solubilization of sem-SWNTs in the presence of lignoceric acid.