Electrochemical Studies of Nanostructured Materials: The Synthesis and Size Effect Dependence of the Adsorption of Organic Molecules and Applications to Biosensors

Nanoporous aluminum oxide films were synthesized and used as the templates to form nanostructured materials. In this work, gold nanowire arrays were formed by this template synthesis method involving electro- and electroless depositions. The applications of both nanoporous aluminum oxide films and gold nanowire arrays to biosensors have been explored for the detection of hydrogen ion and E.coli bacteria. Electrochemical transduction strategies, including Electrochemical Impedance Spectroscopy (EIS) and equilibrium potential measurements were applied. Preliminary experimental results showed that the combination of nanostructured materials and bioarchitecture improved the immobilization of the biological sensing components and the sensitivity of the biosensors. For the hydrogen ion sensor, a linear calibration curve between the sensor output signal and the logarithmic concentration of hydrogen ion precursor was obtained in the concentration range from 10-5 M to 10-2 M. For the E.coli senor, the attachment of every 50 E.coli cells on the surface can be detected by EIS. In order to understand the effect of the nano-scaled structure of the substrates on theperformance of biosensors, electrochemical studies of the adsorption of 1-dodecanethiolon gold substrates with different morphologies were carried out. The adsorption kinetics and the ordering of the adsorbed monolayer of 1-dodecanethiol were studied by electrochemical methods, including Cyclic Voltammetry (CV), Chronoamperometry, and EIS. It was found that the binding of 1-dodecanethiol contained a fast adsorption step followed by a relatively slow reorganization process. The nano-sized structure affected the ordering of the thiol monolayer by a spatial confinement effect and influenced the electrochemical measurements by changing the electrode-electrolyte interfacial properties.