Spectroscopic and scanning probe studies of single-walled carbon nanotubes
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The main topic of this dissertation is the spectroscopic and scanning probe studies of single-walled carbon nanotubes (SWNTs). Current synthetic methods for SWNT growth have limitations such as impurities, poor dispersibility in aqueous solvents, and the lack of ordered arrays. This dissertation includes a three part study to discuss the improvement of the limitations. The first part demonstrates multiple cycles of centrifugation as a method for nondestructive purification. Atomic force microscopy(AFM) and spectroscopies show this mild purification to be effective in order to obtain unbundled and purified high-aspect ratio SWNTs. In second part of this dissertation, the effect of Nafion on the dispersion of SWNT suspensions in bisolvents is discussed. Nafion is an ambipolar dispersant consisting of hydrophilic and hydrophobic groups. Nafion was used as a polymeric dispersant of SWNT suspensions in water/ethanol or water/isopropanol. The defect of SWNT-Nafion suspensions decreased in an aqueous solution with addition of alcohol due to improved dispersion. The debundling of SWNT-Nafion suspensions in water/alcohol also was demonstrated by blue-shifted peaks in near-infrared (NIR) spectroscopy. In the final section, well-ordered arrays of SWNT networks were investigated by depositing carbon nanotubes on self-assembled molecule-coated substrates. Aminosilane and aminothiol were coated on Si/SiO2 and Au substrates, respectively, to produce self-assembled monolayers (SAMs). An improved surface morphology with decreased defects occurred when a high concentration of self-assembled molecules was absorbed for a long period of time.