Study On Preparation, Characterization And Electrocatalytic Properties Of The Polyamide-amine, Ionic Liquid Modified Carbon Nanotube Hybrids

Due to the unique structure and the properties, carbon nanotubes shows attractive prospect in the biomedical field (including the intracellular carriers of biological molecules, biosensors, bioseparation/bioenrichment and biocatalysis and so on). Polyamideamine (PAMAM) dendrimers with precise molecular structure, a large number of surface functional groups, cavity inside of the molecule, controllable relative molecular weight, nanometer molecule size and other characteristics. It can be used in many aspects, such as drug carrier, nanocomposite materials, catalyst and so on. On the other hand, room temperature ionic liquids (ILs) with high ionic conductivity, good biocompatibility and other characteristics. Strong "cation-π" force can generate between ILs and CNTs, which may promote electron transfer between CNTs and biomolecules. This may expend the application of the CNTs electrochemical biosensing. Based on the above analysis, in this paper, combining the advantages of carbon nanotubes with the polyamideamine and ionic liquids, the CNT-PAMAM and CNT-IL hybrids were prepared by using in-situ polymerization, adsorption and other methods. And the microstructure of the hybrids, protein immobilization ability and electrocatalytic properties were investigated in detail by using a variety of analytical methods. The main work is summarized as follows:1. A brief overview of the structure and properties of carbon nanotubes, polyamideamine and ionic liquids, methods to modify carbon nanotubes and their application, developing trends in the field of biomedicine and electrochemical biosensor has been introduced.2. Preparation and characterization of ethylenediamine-modified multi-walled carbon nanotubes (MWCNTs) and its cellular toxicity to MG-63 cell. Ethylenediamine (EDA) was tethered to the surface of multi-walled carbon nanotubes (MWCNTs) under different reaction temperatures. Micro-morphology and surface functional groups of the prepared EDA-functionalized MWCNTs were characterized and indentified by transmission electron microscopy and Fourier transform infrared spectrophotometry. Cytotoxicity of MWCNT-EDA to human osteosarcoma MG-63 cells was evaluated in detail. The results show that under the action of the crosslinking agent, EDA was successfully modified onto the surface of carbon nanotubes; the hybrids with better biocompatibility and lower cellular toxicity to MG-63 cells compared with mixed acid treated MWCNTs.3. Preparation, characterization and protein immobilization ability of MWCNTs/PAMAM complexes. MWCNT-NH2 was used as the initiator core of the reaction, PAMAM with different generations (Different end groups and molecular weight) modified multi-walled carbon nanotubes complexes were prepared by in situ polymerization (repetitive Michael addition and amidation reactions) with appropriate monomer. The MWCNT-PAMAM hybrids were characterized and indentified by Fourier transform infrared spectrophotometry, transmission electron microscopy and electrochemical methods, a preliminary study of protein immobilization ability of the complex was also given. The results indicated that PAMAM with different generations can be successfully modified onto the surface of MWCNTs. The prepared MWCNT-PAMAM hybrids exhibited an improved bovine serum albumin (BSA)-immobilization ability.4. Ionic liquids were functionalized onto the surface of multi-walled carbon nanotube/glass carbon (MWCNTs/GC) electrode by using adsorption method. And glucose oxidase (GOx) was immobilized on the surface of ILs/MWCNTs/GC electrode through Nafion entrapping to to prepare Nafion+GOx/ILs/MWCNTs/GC electrode. The micro-morphology of ILs/MWCNTs/GC electrode and electrocatalytic properties of the Nafion+GOx/ILs/MWCNTs/GC electrode to glucose were investigated by scanning electron microscopy, Fourier transform infrared spectrophotometry and electrochemical methods. On the other hand, the effect of ionic liquid type and modification methods to the electrocatalytic properties of the resulting enzyme electrode were also studied in detail. The results suggested that the modification of MWCNTs/GC electrode with ionic liquids can improve electrocatalytic properties of glucose enzyme electrode; in optimize electrode preparation conditions, enzyme electrode based on N-butyl-pyridine tetrafluoroborate ionic liquids has better electrocatalytic performance (the detection limit of glucose up to 10μM). The Nafion+GOx/ILs/MWCNTs/GC electrode will have potential applications in biofuel cells, electrochemical glucose biosensor.