| dc.description.abstract | Recently, electrochemical DNA biosensors have received particular interest due to their advantages such as sensitivity, selectivity, accurate, simple design, small dimension, inexpensive platforms, and low power requirements. In this thesis, electrochemical DNA biosensors were developed by immobilizing probe DNA onto zinc oxide (ZnO) nanorod surface to detect its complementary sequence. ZnO nanorods were fabricated onto indium-tin-oxide (ITO) coated glass plate by electrodeposition. A survey of electrodeposition parameters including electrodeposition time, ZnCl2 and KCl concentrations was carried out in order to find a good experimental condition which supply a high density and large surface area nanorods as well as fully cover the deposited ITO plane. Generally, the density, distribution, and dimension of ZnO nanorods are more stable and increase with the gain of electrodeposition time, ZnCl2 and KCl content. The results indicated that the electrodeposition acchieved in the solution containing 2.5mM ZnCl2, 0.5mM KCl, 20mM H2O2 in 25 minutes would let the ZnO nanorods grow with extremely high density, next to each other and cover all the survey area of the surface. This parameter was chosen to fabricate ZnO nanorods for electrochemical DNA biosensors. After that, (3 – glycidoxypropyl) dimethylethoxysilane was attached with ZnO nanorods as a linker to immobilize probe DNA. Cyclic voltammetry was employed to evaluate the sensors’ electrochemical properties with assistance of potassium ferricyanide (K3Fe(CN)6) as an electrochemical indicator. Cyclic voltammograms of the sensors revealed that ZnO nanorods had fast electron transfer kinetics with Fe(CN)64-/3- redox couple. The peak current values of our ZnO nanorods are higher in comparison with those of Das et al. ‘s nanostructured ZnO films due to their higher density and larger surface area, suggesting that the developed ZnO nanorods exhibited greater conductivity. The electrochemical response of the DNA–nsZnO/ITO bioelectrodes has also been investigated as a function of complementary target DNA concentration from 10-9M to 10-6M. The results uncovered that DNA-nanorod ZnO/ITO biosensors possesed great detectivity and sensivity due to high density and large surface area of synthesized ZnO nanorods. | en_US |