| Single-walled carbon nanotubes (SWNTs) are molecular wires with carbon tubular structures consisting a single layer of graphite sheet. This unique structure leads to remarkable electrical, mechanical, and chemical properties. The exceptional properties make SWNTs promising materials for a variety of applications, such as nanoelectronic device and chemical sensors. This dissertation describes studies on chemical vapor deposition (CVD) of SWNTs and constructing SWNT chemical sensors. The studies primarily concentrate on overcoming existing barriers in developing SWNT chemical sensors, including variations in device performance and unclear sensing mechanism in aqueous solutions.; 1. A new method was developed to prepare uniform nanoparticles on flat substrates with high coverage. A self-assembled diblock copolymer, polystyrene-block-poly(2-vinyl-pyridine), was used as templates to make catalyst nanoparticles. Iron oxide and cobalt oxide nanoparticles with diameters between 2 and 6 nm were generated on flat surfaces. These nanoparticles served as seeds for producing high-quality SWNT networks on surfaces. Adjusting the size of the nanoparticles led to SWNTs with different diameters. Electrical measurements showed that the SWNT networks were a mixture of semiconducting and metallic SWNTs that could be used to fabricate field-effect devices with reproducible performance.; 2. Performance of SWNT network devices was studied in aqueous solutions. Conductance of the devices was significantly influenced by cationic surfactants present in the solutions. The effect was found to be associated with surfactant adsorption that leads to changes in surface charge density on the surfaces. The devices can reach a detection limit of 10-8M to the presence of the cationic surfactants, about two orders of magnitude lower than that with measured with mechanical methods.; 3. A new process was developed to integrate SWNT devices within microfluidic channels. Liquid flows with laminar properties were used to fabricate the devices in the microfluidic channels. Those devices operated as p-type semiconductor field-effect transistors, and their conductance decreased substantially when charged molecules flowing through the microfluidic channels. By controlling the locations of the flows in the devices, the changes in the conductance were found to arise from these molecules adsorbed around SWNTs. |
