Synthesis, doping and functionalization of carbon nanotubes

• Main Author: Maubane, Manoko Stephina
• Format: Others
• Language: en
• Published: 2011
• Online Access: http://hdl.handle.net/10539/9148

This study reports the synthesis of carbon nanotubes (CNTs) incorporated into polymeric materials for potential use in photovoltaic solar cells. Both undoped (CNTs) and nitrogendoped (N-CNTs) materials were made using the chemical vapor deposition (CVD), catalytic CVD and floating catalyst CVD methods. The procedures produced CNTs with an average yield of 1151 % using a 10 % Fe/Co catalyst supported on CaCO3. This is about three times that produced using 5 % Fe/Co catalyst (average 409 %). Morphology studies showed that the synthesized materials had an average diameter of 30 nm. CNTs were successfully incorporated into polythiophenes (PTh) using an in situ chemical oxidative polymerization method. TEM images showed that the functionalized CNTs in polythiophene, f-CNT/PTh, were thicker (average 192 nm) as compared to pristine CNTs (30 nm). TGA analysis then revealed that the new materials (f-CNT/PTh) were more thermally stable as compared to the pure polymer. N-CNTs were synthesized by the floating catalyst CVD method using toluene, ferrocene and tetramethylethylenediamine. Functionalization of the N-CNTs was then achieved using 3- thiophenecarboxaldehyde and sarcosine in 1,2-dichlorobenzene (Prato reaction). Elemental analysis showed nitrogen incorporation (1.8%) into the N-CNTs and this value tripled after functionalization with the nitrogen donor reagents. Morphology studies showed that the amount of monomer used in forming the N-CNT/PTh nanostructures had an influence on the average diameters of the materials. Different ratios of nanotubes to thiophene monomer by weight were used (1:3, 1:10 and 1:20). It was found that when the amount of thiophene monomer was increased, the overall diameter of the materials increased as did the thickness of the polymer attached onto the N-CNTs. Similar studies were undertaken in order to evaluate the influence of time on the formation of f-N-CNT/PTh nanostructures. Polymerization reactions were carried out for 1 h, 12 h and 24 h and it was found that when the polymerization time increased, the average diameter of the f-N-CNT/PTh also increased, as did the thickness of the polymer attached onto the f-N-CNTs.