We have developed a process for chemical purification of carbon nanotubes for solution-processable thin-film transistors (TFTs) having high mobility. Films of the purified carbon nanotubes fabricated by simple drop coating showed carrier mobilities as high as 164 cm 2 V -1 s -1 , normalized transconductances of 0.78 Sm -1 , and on/off current ratios of 10 6 . Such high performance requires the preparation of a suspension of micrometer-long and highly purified semiconducting single-walled carbon nanotubes (SWCNTs). Our purification process includes length and electronic-type selective trapping of SWCNTs using recycling gel filtration with a mixture of surfactants. The results provide an important milestone toward printed high-speed and large-area electronics with roll-to-roll and ink-jet device fabrication.

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Controlling the morphology of single‐walled carbon nanotubes (SWNTs) is essential to realize their excellent device characteristics in electronics. DNA‐wrapped SWNTs provides an effective, scalable way to fabricate the super‐uniform networks of highly isolated, structure‐sorted SWNTs for thin‐film transistors (TFTs). The DNA‐SWNTs are easily formed into uniform, desired‐density networks of individual nanotubes.

We present an efficient method to extract inner shells of double-wall carbon nanotubes (DWCNTs) in liquid phase. The extraction of inner from outer shells is achieved by cutting the DWCNTs with vigorous sonication in water containing surfactants. The extracted shells are perfectly isolated single-wall carbon nanotubes (SWCNTs) and can be separated using density gradient ultracentrifugation. Statistical analysis using high-resolution transmission electron microscopy reveals that the enrichment of SWCNTs with narrow diameter (0.62-1.0 nm) up to 100% is achieved from highly pure DWCNTs. Furthermore, the (5,4) SWCNTs, which have the diameter of 0.62 nm, are concentrated. Our findings provide a novel way to obtain very narrow, highly isolated SWCNTs with ultraclean surface that have not been obtained in conventional synthesis methods.

We study exciton energy transfer in double-walled carbon nanotubes using femtosecond time-resolved luminescence measurements. From direct correspondence between decay of the innertube luminescence and the rise behavior in outertube luminescence, it is found that the time constant of exciton energy transfer from the inner to the outer semiconducting tubes is ∼150 fs. This ultrafast transfer indicates that the relative intensity of steady-state luminescence from the innertubes is ∼700 times weaker than that from single-walled carbon nanotubes.