Formation of two-dimensional weak localization in conducting Langmuir-Blodgett films

We report the magnetotransport properties up to 7 T in the organic highly conducting Langmuir-Blodgett(LB) films formed by a molecular association of the electroactive donor molecule bis(ethylendioxy)tetrathiafulvalene (BEDO-TTF) and stearic acid CH$_3$(CH$_2$)$_{16}$COOH. We show the logarithmic decrease of dc conductivity and the negative transverse magnetoresistance at low temperature. They are interpreted in the weak localization of two-dimensional (2D) electronic system based on the homogeneous conducting layer with the molecular size thickness of BEDO-TTF. The electronic length with phase memory is given at the mesoscopic scale, which provides for the first time evidence of the 2D coherent charge transport in the conducting LB films.Comment: 5 pages, 1 Table and 5 figure

Flow immunosensor system with an electrode replacement unit for continuous cortisol monitoring for fish

Blood cortisol concentration change in fish is widely used as an indicator of stress. In this study, we developed a flow system which equipped by an electrode replacement unit which can replace sensor conveniently. Multiple sensors sequentially disposed vertically in the holder, and the conductive portion of the sensor to be used was bonded with which set in the bottom of the holder. After measurement, next sensor was inserted into the holder and the replacement would be completed by sequentially moving. The flow system was constructed by replaceable working electrodes which sequence placed in the electrode replacement unit and count electrode into a reaction loop which operated by micro-pump. During the measurement, the potassium ferricyanide was transported into the flow loop and applied a voltage (+250 mV). Output current values were measured both before and after the immune-reaction and the change between them was calculated to determine the cortisol levels. As a result, replacement of the immunosensor performed in only several seconds and a good linear relationship was observed between the sensor response and cortisol in the range of 0–40 ng ml−1. We also performed a measurement of cortisol levels in plasma of tilapia (Oreochromis niloticus) both by proposed biosensor system and ELISA which got a good correlation. We believe that the proposed system can provide a simple and rapid detection of cortisol levels for fish and its principle could be a foundation of a continuous in vivo monitoring of fish cortisol change in fish in the future. Keywords: Electrode replacement unit, Immunosensor, Flow system, Cortisol, Fish stres

Study on the development of carbon nanotube enhanced biosensor for gender determination of fish

To efficiently produce seedlings in aquaculture farms, it is essential to control the ratio of males and females by sex distinguishing. On the other hand, the concentration of 11-ketotestosterone (11-KT), which is contained in the plasma, would be an excellent indicator that is significantly different between males and female fish.However, the concentration of 11-KT is challenging to measure due to its low concentration. In this study, we attempted to develop a high-sense biosensor system enhanced by single-walled carbon nanotubes (SWCNTs) with high conductivity and improved the efficiency and accuracy of fish gender determination. First, a self-assembled monolayer (SAM)was formed on the surface of a disk-type gold electrode, and an anti-rabbit IgG was immobilized on the SAM end.Next, an anti-11-KT antibody was immobilized on this IgG antibody, and then SWCNTs were immobilized on the electrode surface to fabricate the biosensor.Then, we attempted to quantify 11-KT by analyzing the minor electrochemical changes on the electrode surface before and after the reaction of an anti-11-KT antibody with 11-KT as an antigen by cyclic voltammetry.Next, after examining the influence of various conditions (temperature, pH, reaction time) on the response value of this sensor, the specificity of the sensor using other hormones was confirmed.Furthermore, as an application of this sensor to the actual sample, the 11-KT concentration in a Nile tilapia (Oreochromis niloticus) plasma was measured and correlated with the measurement value obtained by the conventional method (ELISA) was compared

Optimization of electrode parameters of NaxCo[Fe(CN)6]0.88/NaxCd[Fe(CN)6]0.99 tertiary battery

A tertiary battery, which is charged by temperature change, has two performance indexes: the thermally induced voltage (Vcell) and discharge capacity (Qcell).Among them, Qcell is determined by the electrode parameters such as charge coefficient [β+ (β−)] of redox potential (V) and weight [m+ (m−)] of the active material in the cathode (anode). In this report, we optimized electrode parameters to maximize Qcell of NaxCo[Fe(CN)6]0.88/NaxCd[Fe(CN)6]0.99 tertiary battery. By this optimization, Qcell reaches 4.9 mAh/g between 293 K and 312 K