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The silver-modified Pd (Ag/Pd) electrode was prepared by underpotential deposition of Cu adatoms, followed by galvanic displacement with Ag atoms to investigate the effect of silver modification on the catalysis and mechanism for glycerol oxidation reaction (GOR) of Pd. Cyclic voltammograms in alkaline glycerol solution exhibited that the Ag/Pd electrode had ca. 100 mV less positive onset potential of the GOR current density and higher peak current density than the Pd electrode, indicating that the GOR activity of Pd was enhanced by surface modification with Ag atoms. In potentiostatic electrolysis at −0.1 V vs. Hg/HgO, GOR mainly began with the oxidation of a terminal OH group for both electrodes, and glycerate and glycolate were major products. The glycolate production was more active for the Ag/Pd electrode. The in situ infrared reflectance-absorption spectra (IRAS) exhibited that GOR products with one or two carbons were detected at lower potentials for the Ag/Pd electrode, indicating that the C C bond cleavage was facilitated by the Ag modification.

Coulometric detection of an analyte in a solution at nanoliter scale was conducted by having redox reactions proceed simultaneously on a platinum electrode. The analyte was oxidized on a part of the electrode in one flow channel and silver was deposited on an array of circular microelectrodes formed in another flow channel at a mixed potential. Coulometric determination of the deposited silver showed a steep change in the generated charge as a result of the complete oxidation of silver. The short measurement time after the start of the coulometry suppressed the increase in background charge, resulting in significant lowering of the detection limit. The lower detection limit for H2O2 was 30 nM (3σ). To improve selectivity and minimize the influence of coexisting interferents, the shifting of the mixed potential, application of a permselective membrane, and electrochemical elimination of the interferents were effective modifications.

A simple evaluation method has been developed for a metal thin layer on a sphere-like plastic microstructure, based on its light-scattering property since, according to our results, the light-scattering intensity of silver-coated microbeads depends significantly on the silver coverage. Our attempt was carried out by using a dark-field microscopy coupled with a spectrometer.

In this paper, we propose a novel method to measure the free spectral range (FSR) of a Fabry-Perot cavity (FPC) using single-frequency modulation (FM) with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a cosine-wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FPC. The transmission light from the FPC is observed and converted to an RF signal by a highspeed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier (LIA) by referring to the oscillator. We theoretically and experimentally demonstrate that the LIA signal become null with a steep slope, when the modulation frequency equals the FSR under the condition that the carrier frequency is slightly detuned from the resonance of the FPC. The experimental results show that the proposed method has the capability to determine the FSR by the null method with a small measurement uncertainty.

Determination of the activity of an enzyme in a solution of nL order was conducted using an electrochemical device with a plug-based microfluidic processing function. β-galactosidase (β-Gal) and adenosine triphosphatase (ATPase) were used as analyte enzymes. β-Gal is often used to be conjugated with antibodies, whereas the latter plays critical roles in cell functions. The activity of the enzymes was determined by measuring the concentration of one of the final products, p-aminophenol (PAP) or hydrogen peroxide (H 2 O 2 ) by coulometry. Preparation of plugs of solutions of predetermined volumes and mixing of solutions was carried out using a T-junction on the device. A partially shallow flow channel structure was designed in the sensing area to improve collection efficiency. The observed output charge was correlated well with the amount of PAP or H 2 O 2 , which served as an indicator of the enzyme activity.

Subclinical mastitis is a common infectious disease of dairy cows. To develop an early diagnostic device for mastitis, we focused our attention to the increase in the number of neutrophils in raw milk of mastitic cows. Since neutrophils secrete superoxide anion (O 2 −), it can be a good indicator to estimate the number of neutrophils. Neutrophils were separated from fat globules using the difference in specific gravity and specific adhesion of neutrophils to P-selectin. Neutrophils trapped in a microchannel were subsequently concentrated in an array of micropillars of a working electrode modified with P-selectin and superoxide dismutase (SOD). The O 2 − secreted from the trapped neutrophils was electrochemically detected. A distinct difference was observed between milk samples containing neutrophils and normal milk samples.

Subclinical mastitis is a common infectious disease affecting dairy cows. To develop an early diagnostic device for this disease, we focused on measuring an increase in the number of neutrophils in raw milk of mastitic cows. Superoxide anions (O(2)(-)), secreted by neutrophils, can be a good indicator of neutrophil concentration, and therefore, the seriousness of the mastitis. In this study, neutrophils in raw milk samples were separated from fat globules in a flow channel using differences in specific gravity and specific adhesion of neutrophils to P-selectin. Neutrophils trapped in the flow channel were subsequently concentrated in an array of micropillars of a working electrode modified with P-selectin and superoxide dismutase. The O(2)(-) secreted from the trapped neutrophils was electrochemically detected. A difference in the detection current was observed between normal and mastitic milk samples. A clear linear relationship between the electric current and cell density was observed.