Zirconium n-butoxide was successfully synthesized using electrochemical method and characterized by IR and 1H-NMR spectra. The influence of various factors on the cell voltage of electrosynthesis process was studied. The cell voltage increased with an increase of electrode distance and current density, but decreased with the increasing Bun4NBr concentration and solution temperature. The ideal conditions for electrosynthesis of zirconium n-butoxide were obtained. The resulting zirconium n-butoxide solution was purified by distillation and n-hexane extraction. Infrared spectra conformed to chemical bonds excellently, and the peak area ratio of nuclear magnetic resonance coincided with number ratio of hydrogen atoms in Zr(OC4H9)4. The purity was close to 99.99%.
The corrosion behavior of high strength low alloy AISI 4135 steel was studied following extended exposure to a Qingdao field environment. When electrochemically active γ-FeOOH was formed in conjunction with easily reducible β-FeOOH, these corrosion products acted to accelerate corrosion attack in the marine splash zone (i.e., steel structure above the water line that is splashed by sea spray). It had also been observed that the pH beneath the rust layer exhibited a minimum during the non-splash part of wet and non-splash corrosion cycling. These acidic conditions contributed significantly to an increase in the rate of localized corrosion, both beneath the rust deposits and within rust cracks and voids within pockets of rust deposits over the steel surface.
Selective electrochemical determination of nicotinamide adenine dinucleotide (NADH) in the presence of ascorbic acid (AA) and uric acid (UA) at a long-length multi-walled carbon nanotube (CNT) electrode is presented. We demonstrate the effectiveness of CNT length toward the electrochemical response due to oxidation of NADH. The long-length CNT is 200 µm (average), whereas normal-length CNT as a comparison is 1 µm (average). In differential pulse voltammetry, the current peaks due to NADH, AA, and UA at long-length CNT electrodes were more distinct than those at normal-length electrode. Electrochemical impedance spectroscopy measurements suggested that the long-length CNT electrode formed a better electron transfer network than the normal-length electrode. The performance of selective determination of NADH are concentration range of 0.030–2.0 mM in the presence of 1.2 mM AA, and 0.059–2.0 mM in the presence of 0.12 mM UA.
A stepwise strategy of mediator-free amperometric biosensor for the detection of catechol was developed based on the covalent bonding of tyrosinase (TYR) onto thionine (TN)-electrodeposited glassy carbon (GC) surface via glutaraldehyde (GA). Prior to the TYR-immobilization, poly(thionine) was prepared on a GC electrode surface by an electrooxidative polymerization of thionine. The TYR/GA/pTN modified electrode was evaluated by SEM and EIS measurements. The terminal amino groups (-NH2) which electrodeposited on the GC surface were cross-linked with protein lysine group (or cysteine group) by GA. The resulting TYR/GA/pTN-immobilized GCE was utilized as a working electrode unit of a catechol-detect biosensor. Catechol was used as model analyte for the evaluation of catecholase activity, and the signal based on the electro-reduction of the enzymatically produced o-quinone species were monitored at −0.05 V vs. Ag/AgCl. The resulting TYR/GA/pTN/GCE biosensor exhibited rapid and sensitive response to catechol (100% response time: ≈5 s, sensitivity: 5.04 µA/mM, detection limit: 6.0 µM. The TYR/GA/pTN/GCE retained 71% of original activity for catechol oxidation after 1 month storage.
One-dimensional electrochemical cellular automata have been extended to incorporate a system of 300 × 300 cells for considering the flow of an electrolytic solution. The random-walk method is employed to deal with this problem in two steps: First, the velocity potential is determined as a steady-state solution. Second, the modified concentration, i.e., the product of the velocity potential and the concentrations of the oxidized and reduced chemical species, is calculated with the simultaneous application of the electrostatic potential. The model is applied to the calculation of the Cottrell current, or the transient response to the step voltage, and the results indicate that the limiting currents linearly increase with increasing flow velocity.