We report on the structural transformation of organic copper phthalocyanine (CuPc) nanowires to hollowed rectangular nanotubes through the use of a hydrothermal process. The CuPc molecules have been chemically self-assembled into a form of nanowires, through reaction with trifluoroacetic acid. The mechanism of the chemical self-assembly for the CuPc nanowires is studied through analyzing the Fourier transform infrared spectra. After the hydrothermal process, it is observed that the a-phase CuPc nanowires are transformed to β-phase CuPc rectangular nanotubes, with crystal-linity in the (-101) direction. From X-ray diffraction patterns, the crystallinity of the CuPc nanowires is enhanced by annealing. The optical and electrical characteristics of the β-phase crystalline CuPc rectangular nanotubes are compared with those of a-phase CuPc nanowires, using ultraviolet and visible absorption spectra and current-voltage (I- V) characteristics. From the gate field-dependent I- V characteristics for a single nanowire/nanotube transistor, improved device performance in terms of the charge carrier mobility and the current on and off ratio have been observed in the β-phase CuPc crystalline rectangular nanotube compared with the self-assembled a-phase CuPc nanowire, because of the relatively strong π-π interaction between the CuPc molecules.
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