The formation of the double hydroxide and its electrolytic reduction at the cathode in zinc-nickel alloy deposition were investigated. By using an EQCM method combined with the electrochemical measurement, it was clarified that the hydrogen generation occurs prior to the alloy deposition and the double hydroxide adheres to the electrode surface. It was confirmed that the electrolytic reduction product of the adhered material on the quartz surface was the zinc/nickel alloy with a Zn : Ni ratio of about 9 : 1, from the analysis by using SEM/EDX. The double hydroxide adsorbed on the cathode surface probably acts as a precursor of the alloy deposition reaction.
The macroscopic fluid motion accompanying copper corrosion under a vertical magnetic field in 3 mol dm−3 nitric acid was visualized and examined using the tracer injection method with a liquid sumi ink. Distribution of the fluid velocity was measured with micro resin particles illuminated by slit laser light. A pair of rotations appeared over the electrode and slowly revolved about an axis. Characteristics of the fluid motion reflect the existence of the myriad vorticity, driven by local Lorentz forces over each active reaction site, and attributed to the non-uniformity of its distribution. This is a novel system with self-organized structure that is dependent on the interaction between local corrosion currents and magnetic field perturbations, which are amplified by the non-linearity of the reaction.
The electrochemical impedance spectroscopy simultaneously with scanning the electrode potential has been developed. By using the present method, the electrochemical impedance in the scanning potential range can be determined with the measurement of potentiodynamic polarization curve. The measured impedance was plotted on the 3-dimensional Nyquist diagram. The time variation of the impedance was compensated, and the impedance at an arbitrary potential was obtained. Furthermore, the linearity of the impedance measurement was discussed, and the present method was applied to the polarization measurement of iron electrode in sulfuric acid solution.
The regeneration mechanism of an ion exchange fabric inserted between the ion exchange membranes in the electrodeionizer has been investigated. The ion exchange fabric comprising cation- and anion-exchange fibers was introduced into the diluting compartment of a five-compartment electrodialysis cell. A significant pH change occurred in the adjacent concentrating compartments when a voltage was applied, probably due to migration of H+ and OH− ions generated by water dissociation in the diluting compartment filled with the ion-exchange fabric. By observing the color change in the ion-exchange fabric adsorbed with phenolphthalein, the water dissociation was found to occur at the boundary between the ion-exchange fabric and an ion-exchange membrane. These findings suggest that water molecules dissociate drastically under a strong electric field at the electrical double layer on the surface of ion-exchange membrane, and the H+ and OH− ions thus formed regenerate the ion-exchange material.
We have already shown that introduction of anthraquinone via a one-carbon linker into the sugar 2′-position of oligonucleotide provides a probe with high affinity and specificity in hybridization to DNA. In this paper, electrochemical properties of the anthraquinone-modified oligonucleotides (AQ-ODN) in an aqueous solution have been investigated to clarify the potential of AQ-ODN as an electrochemical probe of DNA. Positive shift of E1/2 and decrease in the peak current intensity of AQ-ODN were observed upon hybridization. Intercalation of the anthraquinone moiety and increase of the molecular size due to the hybridization are most likely responsible elements for these electrochemical changes.
The nitridation mechanism of the gate silicon dioxide by nitrogen ion implantation was investigated. In nitridation of the gate oxide, the activation energies of the nitrogen concentration are estimated 4.05 eV and 3.97 eV at the interfaces between the polysilicon gate and the gate oxide, and between the gate oxide and the silicon substrate, respectively. Nitridation of the gate oxide proceeds while breaking Si-O bond and forming Si-N bond. At 1100°C RTA for 30 seconds, there is not a difference in gate depletion whether with nitrogen ion implantation or without it.
Ozone is a multi-purpose gas and is widely applied to the industry and agriculture. However, ozone gas in the living environment is harmful to human body. The concentration of ozone gas in workplace environment is limited to below 100 ppb in many countries. At present ozone sensors are expensive, cumbersome and incapable of detecting ppb-level ozone. Here, we report an optical waveguide (OWG) for the determination ozone, which is based on evanescent field adsorption for detection of ozone gas (oxidant) in air. The highly sensitive element of this sensor is a starch-potassium iodide film/K+ ion exchanged glass OWG, fabricated by coating the starch-potassium iodide film over the potassium ion exchanged glass OWG. The low cost and reproducible fabrications make the sensor applicable to be disposable. The device has a short response time, highly sensitive, and detection limit is 10 ppb.