Probing Interactions In Carbon Nanotubes Based Materials Though XANES And STXM

Carbon nanotubes have excellent physical and chemical properties due to their unique one-dimensional tubulose structure. CNTs have vast application in nano-electron devices, hybrid materials and catalysis. For carbon nanotubes, doping and compositing with nanoparticles are effective ways to regulate their properties and promote their practical applications. In this thesis, we used the synchrotron radiation based X-ray absorption near-edge structure (XANES) spectra technique and scanning transmission X-ray microscopy (STXM) technique to study the electronic structure and performance of CNTs and their hybrids. We revealed the mechanism in CNTs grow process, the relation between the functional treatment and hybrid. These studies made theoretical and experimental foundation for prepare CNTs based hybrids with better performances.N-doped carbon nanotubes (NCNTs) were synthesized and their electronic structures had been explored by XANES spectroscopy. With a surface sensitive mode, XANES confirms the N-doping in NCNTs. However, with a more bulk sensitive detection mode of XANES, large amount of gaseous N2have been found to be sealed in NCNTs, even in a high vacuum environment. The encapsulation of the ferrocene residues in carbon nanotubes had been revealed by scanning transmission X-ray microscopy (STXM), which may help for the N2sealing. The results suggest that the easily sealed gas should be taken into consideration for CNT-based applications.The coating of nanoscaled carboxylated carbonaceous fragments on carbon nanotubes (CNTs) has been directly observed in chemical imaging with a concurrent identification of their electronic structure by scanning transmission X-ray microscopy. Moreover, when decorating CNTs with nanoparticles, the CCF coating shades the detection of the CNT/nanoparticle interaction so that the removal of CCFs is mandatory in many foreseen applications.The formation of a carbon coating on carbon nanotubes (CNTs) was also observed in X-ray microscopy experiments. The coating shows some fingerprint features around the π*peak of the C ls XANES spectrum, which were widely observed in literature but attributed to chemical modification or interfacial interaction in carbon nanomaterials.The electronic structure of individual CNTs with different diameters has been investigated by scanning transmission X-ray microscopy (STXM). Various factors that may alter the STXM spectral features in CNT bundles have been discussed. Tube diameter has been found to be proportional to the spectral intensity, whereas it has negligible effect on the spectral shape. Disordered structure in CNTs introduced in the synthesis process was observed, which significantly affected the X-ray absorption spectrum by a reduction of the π*excitation. Moreover, tube-tube interaction in CNT bundles was detected, which can enhance the π*excitation. Insights into the nature of CNT bundles with various electronic structures may provide a new vision to understand the performance of CNT-based devices.