The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

Kinetic regularities of electrochemical oxidation of the methionine anion on platinated platinum

The purpose of this study was the determination of the kinetic regularities of the methionine electrooxidation process on the Pt(Pt) electrode in an aqueous-alkaline medium.The main kinetic regularities of the methionine anion electrooxidation process were determined using by the methods of cyclic voltammetry, coulometry, and electrochemical impedance spectroscopy. The concentration of methionine in the alkaline solution before and after anodic oxidation was determined spectrophotometrically using spectrophotometer UNICO 2800. The measurements were carried out at room temperature both in an argon atmosphere and in an aerated aqueous solution. The results of voltammetric measurements were adjusted for the limiting oxygen recovery current and the charging current of the double electric layer.The range of potentials of the electrochemical activity of the methionine anion on the Pt(Pt) electrode, the number of electrons involved in the anode process, and its kinetic scheme were determined. The main product of the electrooxidation of methionine in an alkaline medium on Pt(Pt) was the methionine sulfoxide anion. It was shown that the electrooxidation of the methionine anion on Pt (Pt) was carried out from the adsorbed state and was irreversible.

Poisoning Effect of CO: How It Changes Hydrogen Electrode Reaction and How to Analyze It Using Differential Polarization Curve

The hydrogen electrode reaction (HER) on Pt electrode in a H2SO4 solution when CO gas was injected/stopped was studied using polarization resistance curve [...]

Activation of Porous Pt Electrodes Deposited on YSZ Electrolyte by Nitric Acid Treatment

The effect of nitric acid treatment on the electrochemical performance of porous Pt electrodes deposited on YSZ (abbreviation from yttria stabilized zirconia) electrolyte was investigated. Two identical symmetrical Pt/YSZ/Pt cells with porous Pt electrodes were fabricated, after which the electrodes of the first cell were kept as sintered, while those of the second cell were impregnated with HNO3 solution. The electrochemical behavior of the prepared electrodes was studied using impedance spectroscopy and cyclic voltammetry. Significant reduction of the polarization resistance of the HNO3-treated electrodes was revealed. The observed enhancement of the electrochemical performance of porous Pt electrodes was assumed to be caused by adsorption of NOx-species on YSZ and Pt surfaces, which promotes oxygen molecules dissociation and transport to the triple phase boundary by the “relay-race” mechanism. The obtained results allow for considering the nitric acid treatment of a porous Pt electrode as an effective way of electrode activation.

Single Entity Behavior of CdSe Quantum Dot Aggregates During Photoelectrochemical Detection

We demonstrate that colloidal quantum dots of CdSe and CdSe/ZnS are detected during the photooxidation of MeOH, under broad spectrum illumination (250 mW/cm2). The stepwise photocurrent vs. time response corresponds to single entities adsorbing to the Pt electrode surface irreversibly. The adsorption/desorption of the QDs and the nature of the single entities is discussed. In suspensions, the QDs behave differently depending on the solvent used to suspend the materials. For MeOH, CdSe is not as stable as CdSe/ZnS under constant illumination. The photocurrent expected for single QDs is discussed. The value of the observed photocurrents, > 1 pA is due to the formation of agglomerates consistent with the collision frequency and suspension stability. The observed frequency of collisions for the stepwise photocurrents is smaller than the diffusion-limited cases expected for single QDs colliding with the electrode surface. Dynamic light scattering and scanning electron microscopy studies support the detection of aggregates. The results indicate that the ZnS layer on the CdSe/ZnS material facilitates the detection of single entities by increasing the stability of the nanomaterial. The rate of hole transfer from the QD aggregates to MeOH outcompetes the dissolution of the CdSe core under certain conditions of electron injection to the Pt electrode and in colloidal suspensions of CdSe/ZnS.

Evaluation of the catalytic activity of graphene oxide and zinc oxide nanoparticles on the electrochemical sensing of T1R2-Rebaudioside A complex supported by in silico methods

Herein, we report on the performance of graphene oxide (GOx) and zinc oxide nanoparticles (ZnONPs) on a platinum (Pt) electrode, immobilized with the human T1R2 sweet taste receptor subunit for the detection of rebaudioside A (Reb-A). The characterization studies performed in this work confirmed the thin-layered structure of GOx and the polydispersed nature of ZnONPs. The elucidation of the mass loss observed by TGA demonstrates the stability of GOx. The cyclic voltammetry results for Pt/GOx revealed good catalytic activity over Pt/ZnONPs for adsorption of the T1R2-Reb-A complex. In addition, a series of computational modelling studies were carried out to better understand the surface adsorption phenomena of GOx and ZnONPs to mimic the layer-by-layer electrode modification strategies independently. The strongest interaction energy observed (−573 kcal mol−1) for the direct interaction of ZnONPs onto the Pt electrode surface, demonstrates a stronger adsorption in contrast to the GOx modified Pt electrode (−23 kcal mol−1). However, the overall results for the layered-nanocomposite revealed that the GOx (−256 kcal mol−1) were more strongly adsorbed in contrast to ZnONPs (−231 kcal mol−1) for the detection of the T1R2-ReB-A complex, demonstrating the reliability of our GOx electrode functionalization strategy. The results of this study can potentially be used to improve the design of rapid Reb-A sensors for the food and beverage industry.