Isolated single-walled carbon nanotubes (SWNTs) adsorbed on an atomically flat and clean Cu(111) surface were studied by means of ultra-high vacuum (UHV) scanning tunneling microscopy and spectroscopy (STM / STS) at 300 K. A dispersion of SWNTs without unzipping molecules was sprayed in vacuum. Subsequently upon annealing of 800 K atomically flat terraces were recovered. STM/STS measurements revealed that some of the SWNTs had similar morphology and electronic local density of states as graphene nanoribbons (GNRs), indicating that the unzipping process could occur even without unzipping molecules.
Dipropylheterocoerdianthrone (DPHCD) was found to be a potential photo-reactive dispersant of single-walled carbon nanotubes (SWNTs). DPHCD was able to well disperse SWNTs in chloroform. DPHCD is easily photo-oxidized by the irradiation of visible light to form the endoperoxide with a bent structure under oxygen or air atmosphere. Then, SWNTs were photo-precipitated from the DPHCD/SWNTs dispersion. The precipitation was able to disperse again after the photochromic reaction to turn back DPHCD from the endoperoxide and sonication. Such photo-induced precipitation was also observed in DPHCD/SWNTs complex film. The SWNTs precipitates were analyzed by FT-IR and Raman spectra measurements, and discussed about selectivity of DPHCD on chirality, and elimination of the dispersant.
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