Characterization and Electrochemical Application of Ruthenium Oxide Thin Films Prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) Method
Date Issued
2010
Date
2010
Author(s)
Huang, Hen-Wen
Abstract
Successive ionic layer adsorption and reaction (SILAR) method has been widely used in the synthesis of group VIA compounds of metals, such as oxides, sulfides, and selenides. It involves cycles of alternate dipping of a substrate into two separate solutions, which are made of a cation precursor and an anion precursor, respectively, and results in the formation of thin films for the intended compound. The thickness of the film formed can be controlled through adjusting the number of reaction cycles. The film synthesized is not limited by the macroscopic area of the substrate. The SILAR method is easy to control, simple, less expensive, and uses less organic solvents. In this thesis research, we studied the chemistry involved in the SILAR synthesis of ruthenium oxide (RO) films on silicon and indium tin oxide (ITO) substrates. The driving forces that determine the formation of RO films are known to include the presences of moderate oxidizing agent and hydroxide ion in the solution as well as heat. In the study, the cation precursor was ruthenium (III) chloride and the anion precursor was generated in the solution via manipulating the driving forces mentioned above. The RO thin films synthesized were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). The XPS spectra revealed that a stronger oxidizing condition favored the formation of RO films having higher oxidation states of ruthenium and a basic condition caused a hydroxide phase to become dominate.
The use in electrochemical sensing of the ITO substrates that were modified by RO films (termed RO/ITO herein) was investigated by using RO/ITO as the working electrode in a three-electrode system for detection of some molecules, such as vitamin C, acetaminophen, and dopamine, in 0.1 M phosphate buffer solutions of pH 7.0. Cyclic voltammograms, chronoamperograms, and the calibration curves for sensing these molecules were established. The RO/ITO electrode prepared under the condition of 1％ H2O2 solution gave the best sensitivity for vitamin C detection, the one made at 60℃ in DI water displayed the largest sensitivity for acetaminophen detection, whereas the electrode fabricated under sodium hydroxide solution of pH 12 offered the greatest sensitivity for dopamine detection. All RO/ITO electrodes made under different oxidizing agent/pH/heat conditions showed a better sensitivity for the detection of dopamine than that of vitamin C and acetaminophen.
Subjects
Ruthenium Oxide Thin Films
SILAR
Electrochemical Application
Type
thesis
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