Tse-Chuan Chou

Nano-crystalline tungsten oxide NO2 sensor

Sensitive porous tungsten oxide nano-crystalline based NO2 sensor was fabricated by thin film microfabrication technique. The sensitivity of this NO2 sensor was at parts per billion (ppb) level. The nano-crystalline porous tungsten oxide film was prepared from WCl 6 by a sol–gel technique. The surface morphology and sensitivity to NO2 of the tungsten oxide films calcined at various temperatures were investigated. The NO2 adsorption behavior on the tungsten oxide surface was carried out by XPS measurement. Experimental results indicated that the tungsten oxide film calcined at 550 ◦ C for 1 h showed the best performance as a sensing material to NO2, and the optimal operational temperature of the sensor was 300 ◦ C. The sensor showed high sensitivity to low NO2 concentration in the range from 50 to 550 ppb with relatively fast response time (∼3 min) and recovery time (∼1 min), respectively.

Polyacrylamide gels with electrostatic functional groups for the molecular imprinting of lysozyme

The system of polyacrylamide incorporated with methacrylic acid and 2-(dimethylamino)ethyl methacrylate was studied for the possibility of imprinting of lysozyme. The results show that approximately 27% (w/w) of the lysozyme template was not able to be extracted from the molecularly imprinted acrylamide polymers. The amount of the lysozyme template able to be extracted was increased by the addition of methacrylic acid. The molecularly imprinted polymer (MIP), which was prepared with 0.573 M acrylamide, 0.573 M methacrylic acid and 0.573 M 2-(dimethylamino)ethyl methacrylate at a total solution concentration of 20% (w/w), was able to adsorb 83% more lysozyme than the non-imprinted polymer. Selectivity of MIP was also studied.

Fabrication of glucose oxidase/polypyrrole biosensor by galvanostatic method in various pH aqueous solutions

The pH effect of pyrrole electropolymerization in the presence of glucose oxidase (GODx) on the performance and characteristic of galvanostatically fabricated glucose oxidase/polypyrrole (Ppy) biosensor is reported. Preparing the GODx/Ppy biosensors in 0.1 M KCl saline solution with various pH containing 0.05 M pyrrole monomer and 0.5 mg/ml GODx at 382 microA/cm2 current density for 100 mC/cm2 film thickness, both the galvanostatic responses and characteristics of these resulted biosensors were obtained. The results revealed that the galvanostatic glucose biosensor fabricated at neutral pH condition exhibited much higher sensitivity than those fabricated at lower or higher pH conditions, and had a good linearity form zero to 10 mM glucose with the sensitivity of 7 nA/mM. Finally, the long-term stability and the kinetic parameters, Michaelis constant and maximum current, of this biosensor were also reported.

Electrochemically promoted photocatalytic oxidation of nitrite ion by using rutile form of TiO2/Ti electrode

Abstract The photocatalytic oxidation of nitrite ion in a NaCl aqueous solution using the rutile form of TiO 2 /Ti as the working electrode was studied. Experimental results indicate that the rutile form of TiO 2 /Ti film electrode has excellent photoactivity by applying a bias potential and irradiation simultaneously. The incident photo-to-current conversion efficiency (IPCE) of this working electrode is a function of the applying bias potential. The photocurrent efficiency of nitrite ion oxidation was 33–40% at a pH of about 7. The oxidation rate of the nitrite ion in brine wastewater using the rutile form of TiO 2 /Ti electrode can be estimated by photocurrent measurements. The applying bias potential, light power and pH value were the major factors affecting the oxidation rate and the photocurrent efficiency of nitrite ion oxidation, while the concentrations of nitrite ion was minor.

An Amperometric Alcohol Sensor by Using Electroless Nickel as Working Electrode

An amperometric alcohol sensor by using electroless nickel as working electrode was developed. The sensing results were affected by the electrolyte composition, deposition time, and temperature of the electroless nickel. The results revealed that the best operating conditions of the electroless nickel were 70 °C deposition temperature, 20 min deposition time, and 2.632 ratio of reducing agent to nickel ion in the solution. The results also indicated that the response time of the prepared alcohol sensor is in the range from 10 to 13 s and the best sensitivity is 8.7 μA/ppm×cm2.

Electrochemical characterisation of a conductive polymer molecularly imprinted with an Amadori compound

Type II diabetes is a disease that is often characterised by elevated levels of advanced glycation end-products (AGEs), e.g. glycated haemoglobin (HbA(1c)), in a patients bloodstream. This glycation reaction occurs when the carbonyl group of a circulating sugar (glucose) reacts with the amino group of the terminal valine residue of a haemoglobin chain, to form an unstable imine. This compound then undergoes an Amadori rearrangement to form the stable Amadori compound N-(1-deoxy-beta-D-fructopyranose-1-yl)-L-valine (Fru-Val). As an initial approach to fabricating a sensor for the Fru-Val component of HbA(1c), molecular imprints of Fru-Val were made in poly-aminophenylboronic acid (p-APBA), using ammonium persulphate as the initiator, on conductive indium-doped tin oxide (ITO) electrodes (nominal working area 0.5 cm(2)). The affinity of the imprints formed in the p-APBA, for fructose and valine as individual molecules, as well as for the complete template used for imprinting (Fru-Val), was assessed electrochemically, by the use of open circuit potential (DeltaE(oc)) measurements. These showed that the imprinted materials when challenged with Fru-Val had an open circuit response of approximately 5.0x10(-3) V. D-fructose (10 mM), a component of the template, when introduced into the cell gave a far more significant change in the open circuit potential (DeltaE(oc)= approximately 2.9x10(-3) V) than did a similar concentration of d-glucose, a non-template carbohydrate (DeltaE(oc)= approximately 4.0x10(-4) V). Non-template structured p-APBA films, made as controls in the absence of Fru-Val, showed negligible response to either D-fructose or D-glucose. Additionally, we have shown that the imprinted films show a progressive reduction in response to sequential additions of D-fructose, implying the saturation of imprinted sites and a limit to non-specific recognition.

Selective hydrogenation of isoprene on eggshell and uniform palladium profile catalysts

Abstract The effects of palladium concentration profile on the selective hydrogenation of isoprene (IP) were investigated by comparing the catalytic performance of well-controlled eggshell and uniform profile catalysts. The catalytic performance test, combined with other complementary characterization techniques, provides the information for fundamental understanding of the relationship between catalyst preparation and performance. Experimental results indicate that the catalyst with an eggshell palladium profile has a higher partial hydrogenation selectivity and less coke formation. The results also indicate that the better activity maintenance for the eggshell catalyst is due to the lower tendency for coke formation from conjugated dienes polymerization. As a result, the eggshell catalyst is much more active, selective and stable than the uniform profile catalyst. In this study, the catalytic reactions were carried out at reaction conditions similar to those of a commercial run: 44°C and 30 atm. The palladium concentration profiles and particle sizes were determined by EPMA (electron probe microanalysis) and TEM (transmission electron microscopy) respectively. The coke deposited on the catalysts was characterized by DSC (differential scanning calorimetry) and the likely coke precursors were identified by GC/MS (gas chromatography/mass spectrometer) spectroscopy.

Effects of magnetic field on the reaction kinetics of electroless nickel deposition

Abstract Effects of a magnetic field on the kinetics of electroless nickel deposition were studied, γ-Alumina powder was used as substrate and mechanical agitation ensured that deposition proceeded under chemical kinetic control. A reaction mechanism based on chemisorption was proposed for electroless nickel deposition and the effects of magnetic field were discussed. The results indicate that electroless nickel deposition is a free radical reaction and an induction period was found. Experimental results of the magnetic field effects on the reaction orders with respect to both the nickel ion and hypophosphite ion correlated well with the theoretical analyses. The effect was due to the spin rephasing between the singletphased and triplet-phased radical pairs of Ni + · a and the hydrogen atom, respectively. The activation energy was decreased by the magnetic field because more singlet-phased radical pairs were obtained from the faster rephasing of triplet-phased radical pairs induced by the magnetic field. The empirical rate equations with and without the magnetic field were obtained. Change of frequency factors indicated that the spins of free radical pairs were different.

Paired electro-oxidation. I. Production of benzaldehyde

Oxidation of toluene to benzaldehyde by Mn3+ and OH free radicals, generated in the anodic and cathodic reactions respectively, was carried out simultaneously in the cathodic and anodic compartments of a cell. The selectivity of benzaldehyde was very high in both the anodic and cathodic reactions. The maximum total current efficiency for benzaldehyde production in the paired electrooxidation was 171%.

Criteria for Designing a Polypyrrole Glucose Biosensor by Galvanostatic Electropolymerization

The polypyrrole (Ppy) glucose biosensor prepared by the galvanostatic electropolymerization of pyrrole monomer in the presence of glucose oxidase (GODx) in a saline solution (pH 7.0) with a platinum electrode is reported. The performances of the biosensor prepared under the different conditions were investigated and compared. The colored-morphology of Ppy/GODx first presented with the optical microscope revealed that the immobilized GODx were over-covered by the polypyrrole which was a serious diffusion barrier of glucose when the pyrrole monomer concentration was higher than 0.075 M. Considering the sensitivity and selectivity, the optimal condition for galvnostatically preparing this biosensor was 0.05 M pyrrole, 0.5 mg/mL GODx, 382 μA/cm2 applied current density, and 50 mC/cm2 film thickness. Finally, the linear range of this optimized glucose biosensor was from zero to 12 mM and the sensitivity of that was 11 nA/mA. The kinetic parameters of Km and Imax for this sensor were 48.8 mM and 628 nA, respectively. The criteria for designing an optimal glucose biosensor by the galvanostatic electropolymerization were obtained.