Preparation Of Carbon Nanotube Based Nanostructured Thin Films Via Layer-by-Layer Self-assembly

Since it has been discovered in 1991 by Iijima, carbon nanotubes (CNTs) with unique properties and various applications in optical, electrical, magnetic and biological biosensors have been intensively investigated widely by researchers. Carbon nanotubes-polyelectrolyte multilayer thin films have been assembled using a layer-by-layer (LBL) self-assembly technique for various applications.However, carbon nanotubes are insoluble in general organic solvents and water due to chemical inert, it's a big challenge to obtain well-dispersed carbon nanotubes water dispersion. Therefore, surface modification of carbon nanotubes is necessary before they could be used in layer-by-layer self assembly. In this thesis, we use a polymer wrapping method to disperse MWCNT, which are then used as building blocks to construct multilayer thin films with polyelectrolyte, gold nanoparticles (Au NPs), polypyrrole (PPy) and titanium (IV) bis (ammonium lactato) dihydroxide (TALH). UV-visble absorption spectroscopy, scanning electron microscope and cyclic voltammetry are used to characterize the growth, morphology and electrochemical properties of the composite thin films, and the application has also been studied.The first chapter introduces carbon nanotubes and layer-by-layer self assembly technique, puts forward our research purposes and main work. In the second chapter, a poly (sodium 4-styrene-sulfonate) (PSS) wrapping method was used to disperse multi-walled carbon nanotubes, the result well-dispersed carbon nanotube water solution was negatively charged, so it can be assembled with a positively charged polyelectrolyte poly (diallyldimethylammonium chloride) (PDDA) via LbL self-assembly, then gold nanoparticles were absorbed on the outermost of MWCNT/PDDA multilayer films. The electronic conductivity of composite films was enhanced obviously and has excellent electrocatalytic activity towards the oxidation of nitric oxide (NO). In the third chapter, positively charged multi-walled carbon nanotube water solution was made by using a same PDDA wrapping method. This MWCNT dispersion can be LbL assembled with a negatively charged electrolyte polypyrrole (PPy) to form MWCNT/PPy hybrid thin films, which could then absorb horseradish peroxide (HRP) on the outside and be used as a hydrogen peroxide (H₂O₂) biosensor. The hybrid thin film electrode has good conductivity and good electrocatalytic activity to the reduction of H₂O₂. The fourth chapter, we LbL assembled the positively charged PDDA-MWCNT dispersion and negatively charged titanium (IV) bis (ammonium lactato) dihydroxide (TALH) to obtain a MWCNT/TiO₂ multilayer thin films. UV-vis spectroscopy was used to characterize the growth of thin films assembled in different pH of TALH solution, and the effect of the annealing treatment on the thin films was also investigated.