PQQ-dependent fructose dehydrogenase (PQQ-FDH), which is able to transfer electrons to metal electrodes, was immobilized onto an extended gold-gate of a chemical charge-coupled device (chemical CCD) to measure the catalytic electron transfer in the presence of the substrate. Rapid decrease of the output voltage of the FDH-immobilized gold-gate chemical CCD was observed by the addition of fructose and the extent of the decrease depended on the concentration of fructose. Furthermore, the output profile showed substrate-specificity of FDH. These results strongly suggest that enzymatic oxidation of the substrate and the subsequent direct electron transfer from the enzyme to the gold-gate was detected sensitively with the gold-gate chemical CCD. This finding will open a new field of bioelectronic sensors and devices.
Calcinations of a W12O41·[C5H5N(CH2)12CH3]7.8 complex under an argon atmosphere gave nano-sized WO2/carbon clusters composite materials. ESR spectral examinations suggest the possibility of an electron transfer from the carbon clusters to the WO2 particles.
The filling of trenches in ULSI interconnect structure by electroless copper deposition was investigated for the effect of bath additives. The additive effect was found to depend strongly on the reducing agent used in the bath. Void-free trench-filling was achieved by using polyethylene glycol (PEG) as an inhibiting additive in the bath containing glyoxylic acid as the reducing agent, while the combined addition of 8-hydroxy-7-iodo-5-quinoline sulfonic acid (HIQSA) and PEG was necessary for achieving void-free filling in the bath containing formaldehyde as the reducing agent. The effect of PEG on trench filling in the former bath was studied in detail based on electrochemical measurements. It is suggested that the rinse water remaining in trenches before electroless deposition causes a decrease in PEG concentration at the trench bottom during copper filling. The addition of PEG was found to shift the deposition potential in the negative direction. A new potential measuring apparatus was devised and used in model experiments, which revealed that the deposition potential depends on the local concentration of PEG at the trench bottom, where it is expected to be low. The observed preferential growth of copper deposit at the trench bottom is thus attributed to the effects of the variation of PEG concentration within the trenches on the deposition rate and potential.
The influence of chloride ion on the oxidation and dissolution of platinum has been studied by using Electrochemical Quartz Crystal Microbalance (EQCM) in combination with Inductively Coupled Plasma (ICP) analysis to clarify the deterioration mechanism of platinum catalyst in the Polymer Electrolyte Fuel Cell (PEFC). Platinum was electroplated on an Au-QCM electrode in 2% H2PtCl6 solution and used as the working electrode. A mass gain of the platinum electrode was observed during anodic polarization in 0.5 M H2SO4 solution ([Cl−] free solution) due probably to the formation of Pt oxide. The oxide film was not stable in the whole range of potential used in this study. On the other hand, a mass loss due to the dissolution of Pt as chloride complex ions was observed in more positive potentials than 0.85 V vs. SHE in chloride-containing solutions. As the chloride concentration increased, platinum showed a higher dissolution rate with the formation of chloride complexes, PtCl42− and PtCl62−. The amount of dissolved PtCl62− tended to increase with the increase of anodic potential limit. The EQCM results revealed that the dissolution of Pt was accelerated when potential was cycled between cathodic and anodic limits. The ICP analysis of the solution after anodic polarization supported the results obtained by EQCM.