Covalent Modification Of Carbon Nanotubes And Its Application In Electrochemical Analysis

The current research involved covalent functionalization of single-wall carbon nanotubes (SWCNTs) and its application in the field of electrochemical analysis. The following two aspects were included.Covalent functionalization of SWCNTs with polymer was accomplished by emulsion polymerization using sodium dodecylbenzene sulfonate (SDBS) as emulsifying agent. The polymerizable vinyl groups were incoperated on SWCNTs surfaces by successive chemical reaction process, including oxidation, hydroxylation, and vinylation reactions. The as-prepared vinylated SWCNTs were then dispersed in water in the presence of SDBS, resulting in the exfoliation of SWCNT bundles into individual SWCNTs and formation of SWCNT micelles simultaneously. Subsequent addition of methyl methacrylate (MMA) resulted in its absorption into the formed SWCNT micelles due to the interactions between the monomer and the tube surface functionalities. Grafting copolymerization of MMA with vinyl groups on the SWCNT surface was thus performed in the micelles to produce poly(methyl methacrylate) (PMMA) functionalized SWCNTs. Thermogravimetric analysis (TGA) indicated that the average polymer content in the functionalized SWCNTs ranged from 42 wt% to 63 wt%, depending on the pre-emulsion time of monomer. Further characterization was accomplished by transmission electron microscopy (TEM), which was utilized to image SDBS exfoliated SWCNTs and polymer-functionalized SWCNTs.Carbon nanotubes have been increasingly used in electrochemical analysis because of their excellent electrical conductivity and good catalytic activity. A new electrochemical sensor combined with the excellent electrochemical properties of SWCNTs and the recognition ability ofβ-cyclodextrin (β-CD) to guest molecule was fabricated in this paper. Firstly,β-CD was covalently incorporated on the surface of SWCNTs through the reaction of carboxylic chloride groups on the SWCNTs surface with mono-6-(hexanediamino)-β-cyclodextrin (HDA-β-CD), resulting inβ-CD functionalized SWCNTs (SWCNT-β-CD). Subsequently, SWCNT-β-CD modified glassy-carbon electrode (GCE) was constructed by dropping SWCNT-β-CD suspension onto the GCE. The modified GCE was used to simultaneously determine the mixture of ascorbic acid (AA) and uric acid (UA). The electrochemical behaviors of AA and UA were investigated by cyclic voltammetry (CV). The results demonstrated that SWCNT-β-CD modified GCE could discriminately determine AA and UA with their respective oxidation peaks. An enhanced analytical performance was obtained compared with non-modified GCE.