Ming Chang Yang

Electrodeposition of Indium Antimonide from the Water-Stable 1-Ethyl-3-methylimidazolium Chloride/Tetrafluoroborate Ionic Liquid

The electrodeposition of indium antimonide was investigated in a basic l-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid containing In(III) and sb(III). Energy-dispersive spectroscopy data indicate that the composition of the In-Sb code-posits can be varied by deposition potential and concentration of In(III) and Sb(III) in the solution. At potentials where the deposition of antimony and indium is mass-transport limited, InSb compound can be obtained from solutions containing equal moles of Sb(III) and In(III). Analysis of the X-ray diffraction patterns indicates that the crystallinity of the electrodeposits is affected strongly by deposition temperature. The crystallinity of the deposits improves as the deposition temperature increases and crystalline InSb can be directly electrodeposited at 120°C. Photocurrent experiments indicate that the electrodeposited InSb was a p-type semiconductor. Infrared absorption measurements of the InSb deposits indicate a direct optical transition with an optical bandgap of 0.20 eV.

A microfluidic system with integrated molecular imprinting polymer films for surface plasmon resonance detection

This paper presents a novel microfluidic system with integrated molecular imprinting polymer (MIP) films designed for surface plasmon resonance (SPR) biosensing of multiple nanoscale biomolecules. The innovative microfluidic chip uses pneumatic microvalves and micropumps to transport a precise amount of the biosample through multiple microchannels to sensing regions containing the locally spin-coated MIP films. The signals of SPR biosensing are basically proportional to the number of molecules adsorbed on the MIP films. Hence, a precise control of flow rates inside microchannels is important to determine the adsorption amount of the molecules in the SPR/MIP chips. The integration of micropumps and microvalves can automate the sample introduction process and precisely control the amount of the sample injection to the microfluidic system. The proposed biochip enables the label-free biosensing of biomolecules in an automatic format, and provides a highly sensitive, highly specific and high-throughput detection performance. Three samples, i.e. progesterone, cholesterol and testosterone, are successfully detected using the developed system. The experimental results show that the proposed SPR/MIP microfluidic chip provides a comparable sensitivity to that of large-scale SPR techniques, but with reduced sample consumption and an automatic format. As such, the developed biochip has significant potential for a wide variety of nanoscale biosensing applications.

An 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-immobilized electrode for the simultaneous detection of dopamine and uric acid in the presence of ascorbic acid

An 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS)-immobilized carbon nanotube (CNT) electrode was used to simultaneously detect dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) with differential pulse voltammetry. When ABTS was immobilized onto the CNT electrode in the presence of DA, UA and 100 μM AA, the sensitivity to DA increased from 0.600 (±0.013) to 1.334 (±0.010) μA/μM in the concentration ranges of 0.90-10 μM and 1.87-20 μM, respectively, and the sensitivity to UA increased from 0.030 (±0.005) to 0.078 (±0.006) μA/μM in the concentration ranges of 2.16-240 μM and 3.07-400 μM, respectively. These findings demonstrate that the ABTS-immobilized CNT electrode attained a higher sensitivity to UA and also a wider linear range of concentrations.

Micro and nano scale metal oxide hollow particles produced by spray precipitation in a liquid-liquid system

Microfabrication of Al2O3, TiO2 and ZrO2 hollow particles were carried out by spray precipitation that the fast polymerization is induced from dehydration or acid–base neutralization on the interface of the sprayed droplet to form rigid shell structure, and then removing the remained solvent within the shell. High yield of the smooth hollow particles can be achieved by selecting a highly polymeric precursor, which has higher surface tension, viscosity and density than those of the precipitation agent. In this work, micro to nano scaled Al2O3, TiO2, and ZrO2 hollow particles are obtained, respectively, by spraying their precursor solutions including: aluminum chlorohydrate, titanium chloride, and zirconly chloride into the precipitation agents including acetone, triethylamine and tributylamine. Subsequently, the remained water in the inner shell particles are allowed to vaporize carefully and calcinated. A bottle structure was demonstrated by increasing the momentum of sprayed droplets to impact with the precipitation agent.

Impedance Analysis of Working PEMFCs in the Presence of Carbon Monoxide

A three-electrode membrane electrode assembly including anode, cathode, and pseudoreference electrode was used in a working proton exchange membrane fuel cell PEMFC. The pseudoreference electrode was directly prepared onto a Nafion membrane by an impregnation-reduction method. The electrochemical behaviors of the anode and cathode were separately studied when this three-electrode cell performed. The CO tolerance of the fuel cell with various anode compositions of Ru/Pt 0.12‐3.33 was investigated with both polarization curves and ac impedance analysis. An equivalent circuit model was proposed to explain the impedance spectra for both the anode and the cathode. With the presence of CO, the overpotential due to CO poisoning on the anode was due to the increase of both charge-transfer resistance and ohmic resistance in the catalytic layer.

Platinum Electrodes Modified by Tin for Electrochemical CO Sensors

Carbon monoxide, a toxic gas, is produced from incomplete combustion of fuel, e.g., gasoline and natural gas, and the amperometric CO sensor is one of the commonly used sensors. One of the common electrodes for this type of sensors is catalytic Pt on a Nation membrane. The Pt electrode modified with Sn was studied to improve the sensitivity of CO. In the present study, the sensitivity of CO on a Sn-modified Pt/Nafion assembly was 5.5 times larger than that on a Pt/Nafion assembly in the concentration range 0-400 ppm. With a Pt W /Nafion/Pt C assembly, the CO sensing current on a Sn-modified electrode was also about three times larger than that on a non modified electrode in the concentration range 0-100 ppm.

Electrodeposition of Nickel Oxyhydroxide Films Through Polymer Masks

Electrochromic materials have attracted much attention for devices including ``smart windows`` and displays. Nickel oxyhydroxide films were electrodeposited through gelatin masks, whose thicknesses may control the optical transmittances of the deposited electrochromic films. The difference of transmittance, {Delta}T{sub 540}, between bleaching and coloration states at wavelength of 540 nm has a linear relationship with the gelatin mask thickness. {Delta}T{sub 540} increased if nickel oxyhydroxide was prepared in agitated electrolyte. The electrodeposited films, prepared with gelatin masks, may have higher stability. These results showed the feasibility of fabricating an electrochromic device with a controlled image whose contrast and brightness are adjustable with potential or current.

Ultrasonic irradiation effect in the impregnation-reduction process of preparing Pt/Nafion(®) NH4/+ sensor

A systematic study on the ultrasonic irradiation effect in the impregnation-reduction (I-R) process for preparing a Pt/Nafion electrode was carried out in a flow-injection system of ammonium ion detection. Both the impregnation and the reduction stages were affected by ultrasonic irradiation which increased the sensing currents of electrodes. Moreover, the effect of ultrasonic irradiation was found more significant in the reduction process than in the impregnation process. The relationship between sensing current and power of ultrasonic irradiation was also obtained. The specific active surface area of the Pt/Nafion electrodes were evaluated by the cyclic voltametric technique. Meanwhile, the surfaces of the electrodes were characterized by XRD and SEM.

The Use of Air Fuel Cell Cathodes to Remove Contaminants from Spent Chromium Plating Solutions

Abstract Results from experiments using an impregnation‐reduction (I‐R) Pt ? Nafion membrane electrode assembly (MEA) in an air fuel cell cathode to remove contaminants (Cu(II), Ni(II), and Fe(III)) from spent chromium electroplating baths are presented in this study. A platinum‐carbon (Pt‐C) ? Nafion MEA and a Pb planar cathode were also used for comparison. The average removal rates of Cu(II) and Ni(II) were almost the same (0.39 and 0.40 mM hr‐1 (or 0.117 and 0.12 mmol h‐1), respectively) but higher than that of Fe(III) (0.16 mM hr‐1, or 0.048 mmol hr‐1) in accordance with the Nernst‐Planck flux equation. The removal rates for the same cation were independent of the cathode used. The average removal rate of each impurity was approximately proportional to the product of its initial concentration and separator area/anolyte volume ratio using Pb cathodes. Under constant current conditions the system using the Pt‐C ? Nafion cathode needed the highest cell voltage, about 3 V more than needed for the system with the Pt ? Nafion cathode. The cell voltage required using the Pt ? Nafion cathode was similar to that using the conventional planar Pb cathode. Analyses of cathode deposits by SEM/EDS and XPS techniques indicated they were minimal on the Pb and Pt ? Nafion cathode and more apparent on the Pt‐C ? Nafion cathode. The primary deposits on the Pb cathode were chromium oxides (e.g., Cr2O3) with minor amount of lead chromate (lead dichromate or lead trichromate) and other chromium solids (Cr black). As expected, the dominant deposit on the lead anode surface was PbO2‐

A study on monitoring of vinyl chloride gas by an indirect sensing method

An indirect sensing method is described for vinyl chloride with an amperometric sensor connected to a prepyrolysis column. Significant sensing ability to the pyrolyzed gas, produced from pyrolysis of 0-30 ppm vinyl chloride gas, was obtained with a Pt/porous alumina substrate assembly. Furthermore, the sensing current was proportional to the concentration of vinyl chloride gas in the investigated concentration range. The sensitivity and sensing limit for vinyl chloride were observed as functions of pyrolysis temperature, gas flow rate, and applied potential. Preferable sensing parameters were 400°C, 150 mL min -1 , and 1.2 V (vs. Ag/AgCl), in which the sensing reaction was controlled by gas diffusion. Effect of porosity of porous alumina substrate on the sensing performances was also studied. The electroactive species, which was contained in the pyrolyzed gas and electrochemical oxidized on the sensing electrode, was suggested to be hydrogen chloride vapor.