Physics of one-dimensional hybrids based on carbon nanotubes

PhD ceremony: Mr. J. Gao, 12.45 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Physics of one-dimensional hybrids based on carbon nanotubes

Promotor(s): prof. M.A. Loi

Faculty: Mathematics and Natural Sciences

In this thesis, we focus on two kinds of SWNT based one-dimensional organic-inorganic hybrids. We aimed to understand the fundamental properties and to find applications in optoelectronic device.

‘Peapods” in this work correspond to the hybrids in which organic small molecules are encapsulated inside single-walled carbon nanotubes (SWNTs). We introduce a family of peapods with thiophene oligomers. Configuration and kinetics of the encapsulated molecules inside the SWNTs were demonstrated by high-resolution transmission electron microscopy showing two arrays of molecules parallel to the SWNT walls. PL emission of the peapods compared to that of 6T in solution shows broader and less resolved feature. The PL lifetime of the peapods becomes shorter than that of the 6T molecule in the same solvent, indicating an interaction between ‘pea” and ‘pod” molecules. Theoretical calculations demonstrate van der Waals interaction as the bonding mechanism between the tube and the encapsulated molecule.

The other object has been explored in this study is named ‘polymer-wrapped SWNTs”. We investigated the mechanism of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO)-carbon nanotube interaction in toluene, which leads to a selective sorting of only 5 kinds of semiconducting SWNTs. The interaction is dominated by the octyl-octyl zipping mechanism that locks the polymer chains on the nanotubes. We also used PFO sorted semiconducting SWNTs in the application of field effect transistors (FETs). Extrinsic effects on the electrical characteristics of SWNT FETs were studied. Furthermore, we observed that SWNT dispersions are influenced by the molecular weight and the structure of side-chains of the polymer.