Fabrication and Characterization of Carbon Nanotubes for Biomedical Applications

Rong, Zhiyang

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Fabrication and Characterization of Carbon Nanotubes for Biomedical Applications

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Recently, nanomaterials have been vigorously studied for the development of biosensors. Among them, carbon nanotubes (CNTs) have stimulated enormous interest for constructing biosensors due to their unique physical and chemical properties such as high surface-to-volume ratio, high conductivity, high strength and chemical inertness. Our study is to develop a general design of biosensors based on vertically aligned CNT arrays. Glucose biosensor is selected as the model system to verify the design of biosensors. In the preliminary design, glucose oxidase (GOx) is attached to the walls of the porous alumina membrane by adsorption. Porous highly ordered anodized aluminum oxide (AAO) prepared by two-step anodization are used as templates. Deposited gold on both sides of template surfaces serve as a contact and prevent non-specific adhesion of GOx on the surface. In order to find out optimized thickness of gold coating, the oxidation and reduction (redox) reaction in [Fe(CN)6]3Â¨C /[Fe(CN)6]4Â¨C system is monitored by Cyclic Voltammetry (CV). Subsequently, enzymatic redox reaction in glucose solutions is also attempted by CV. We expect protein layers with GOx form a conductive network. However, no obvious enzymatic redox reaction is detected in the voltammogram. To take advantage of the attractive properties of CNTs, the design of enzyme electrodes is modified by attaching CNT onto the sidewalls of AAO template nanopores and then immobilizing GOx to the sidewalls and tips of CNTs. AAO templates provided vertical, parallel, well separated and evenly spacing nanochannels for CNT growth. Cobalt is used as a catalyst to fabricate CNTs. As a result, multi-walled carbon nanotubes (MWCNTs) are fabricated inside the AAO templates by catalytic chemical vapor deposition (CCVD). Characterization of AAO templates and cobalt electrochemical deposition are employed by scanning electron microscope (SEM), and energy dispersive X-ray spectrometry (EDS). Detailed structure and texture of CNTs are examined by transmission electron microscope (TEM).

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