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A simple amperometric detection (AD) method based on mesoporous platinum (Pt) electrodes has been developed for the determination of sugars (glucose, fructose, and sucrose) with high-performance anion-exchange chromatography (HPAEC). The amperometric detection is based on the direct oxidation of sugars on mesoporous Pt films formed on a gold electrode. The mesoporous Pt electrode (roughness factor of 243) sensitively responded to glucose, fructose, and sucrose in 80 mM sodium hydroxide solution as an alkaline mobile-phase for HPAEC. Under the optimum conditions, the limits of detection (S/N = 3) in these sugars were 0.24, 0.29, and 1.8 mM, for glucose, fructose, and sucrose, respectively. The reproducibility (relative standard deviation) of the measurements was less than 3.5%. The present method was applied to the determination of sugars in apple juice. The recoveries for all sugars ranged from 97 to 99%.

A new two-point calibration method for the subcutaneous amperometric continuous glucose sensor is reported. The proposed method is based on direct measurement of the background current (I(o)) using a non-enzyme electrode. For in vivo test, three electrodes were implanted in rabbits. Two of the three were identical needle-type enzyme electrodes with perfluorinated polymer outer layers (Pt/enzyme layer/Kel-F/PTFE/Kel-F/Nafion) that were placed in subcutaneous tissue and in a vessel (ear artery), respectively. And one non-enzyme electrode with exactly the same membrane composition as those of other two was in the subcutaneous layer to measure the background current. Implantation in the subcutaneous layer generated many crevices on the protecting layers of the electrodes. The signals from enzyme electrodes were effectively corrected by the measured background current from the non-enzyme electrode. In addition, a telemetric monitoring system was developed and evaluated for in vivo continuous glucose monitoring in order to alleviate the problems of motion artifact.

Herein, sol–gel-processed Y2O3 resistive random-access memory (RRAM) devices were fabricated. The top electrodes (TEs), such as Ag or Cu, affect the electrical characteristics of the Y2O3 RRAM devices. The oxidation process, mobile ion migration speed, and reduction process all impact the conductive filament formation of the indium–tin–oxide (ITO)/Y2O3/Ag and ITO/Y2O3/Cu RRAM devices. Between Ag and Cu, Cu can easily be oxidized due to its standard redox potential values. However, the conductive filament is easily formed using Ag TEs. After triggering the oxidation process, the formed Ag mobile metal ions can migrate faster inside Y2O3 active channel materials when compared to the formed Cu mobile metal ions. The fast migration inside the Y2O3 active channel materials successfully reduces the SET voltage and improves the number of programming–erasing cycles, i.e., endurance, which is one of the nonvolatile memory parameters. These results elucidate the importance of the electrochemical properties of TEs, providing a deeper understanding of how these factors influence the resistive switching characteristics of metal oxide-based atomic switches and conductive-metal-bridge-filament-based cells. [ABSTRACT FROM AUTHOR]

In this study, we fabricated sol-gel-processed Y2O3-based resistive random-access memory (RRAM) devices. The fabricated Y2O3 RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require the forming process. The long-term stability of the RRAM devices was investigated. The Y2O3 RRAM devices with a 20 nm thick Ag top electrode showed an increase in the low resistance state (LRS) and high resistance state (HRS) and a decrease in the HRS/LRS ratio after 30 days owing to oxidation and corrosion of the Ag electrodes. However, Y2O3 RRAM devices with inert Au-passivated Ag electrodes showed a constant RRAM device performance after 30 days. The 150 nm-thick Au passivation layer successfully suppressed the oxidation and corrosion of the Ag electrode by minimizing the chance of contact between water or oxygen molecules and Ag electrodes. The Au/Ag/Y2O3/ITO RRAM devices exhibited more than 300 switching cycles with a decent resistive window (>103). They maintained constant LRS and HRS resistances for up to 104 s, without significant degradation of nonvolatile memory properties for 30 days while stored in air. [ABSTRACT FROM AUTHOR]

In this letter, sol–gel-processed SnO2 films were deposited, with thicknesses varying from 3.5 to 5.0 nm, by controlling the concentration of the precursor solutions. Through electrical and spectroscopic investigations, it was found that the optical energy bandgap and the electron affinity were affected by the quantum confinement effect and Burstein–Moss effect. Moreover, the increased barrier height between Au and SnO2 semiconductors was enhanced when thinner SnO2 layers were used, resulting in strong Schottky diode characteristics. This letter allows one to examine the size scaling effects of ultrathin electrical devices with SnO2 channel layers. In addition, a generalized energy band diagram derived from the bandgap broadening in ultrathin SnO2 semiconductors is presented, which will allow the elucidation of the carrier transport mechanism and optical properties of quantum confined SnO2 semiconductor-based optical and electrical devices. [ABSTRACT FROM AUTHOR]

A sol-gel-processed ZrO2 layer was used as an active layer for a resistive random-access memory (RRAM). With top Ag electrodes, the fabricated devices show conventional bipolar switching memory properties. The impacts of device size and ZrO2 film thickness on device performance were investigated. The scaling of the device area and the successful increase in ZrO2 film thickness increased the high-resistance state (HRS)/low-resistance state (LRS) ratio values and improved the non-volatile memory properties, such as retention and endurance. The fabricated ITO/ZrO2/Ag RRAM shows good retention and endurance properties. The HRS and LRS were found to last for 104 s without any significant degradation. [ABSTRACT FROM AUTHOR]

Abstract: To find the best operating conditions and oxygen electrode catalyst of the PEM unitized regenerative fuel cell (URFC) system, we examined the effect of reaction conditions and the performance of several bifunctional electrocatalysts for oxygen electrode in a single cell PEM URFC system. When Pt black was employed for both electrodes, the URFC performance improved with increasing cell temperature up to 70 °C and catalyst loading up to 6.7mgcm−2. Among the catalysts prepared in the present study for oxygen electrode, fuel cell performance decreased in the order of Pt black > PtIr > PtRuO x > PtRu ∼ PtIr > PtIrO x , whereas, water electrolysis performance decreased in the order of PtIr ∼ PtIrO x > PtRu > PtRuIr > PtRuO x ∼ Pt black, showing significant performance improvement by addition of second metals such as Ir or IrO x to Pt black. Consequently, PtIr had the best URFC performance with high round-trip efficiency and stability during the cycling operation of the URFC system. Therefore, PtIr is promising as an oxygen electrode of the PEM URFC system. [Copyright &y& Elsevier]

Abstract: DNA-modified electrode has been used for the highly selective and sensitive electrogenerated chemiluminescent determination of phenothiazine drugs in urine sample. Double-stranded calf-thymus DNA was immobilized by covalently bonding to a conducting polymer containing a carboxylic group, which was electrochemically polymerized on a glassy carbon electrode with a monomer of thiophene-3-acetic acid. Phenothiazine derivatives were selectively preconcentrated onto the DNA-modified electrode due to their intercalative binding properties with DNA double helix. The phenothiazine derivatives as coreactants were then sensitively detected with the electrogenerated chemiluminescence. The present method can detect phenothiazine drugs in the linear range of 1.0×10−8 M–1.0×10−5 M with detection limits of nanomolar concentration level. Moreover, the interference from ascorbic acid, glutamic acid, and amino acids was almost negligible because of electrostatic repulsion between the negatively charged DNA-modified electrode and anionic interfering species. The present detection method exhibited 95.2% recovery in human urine sample. Therefore, the present method can be applicable for real sample analysis. [Copyright &y& Elsevier]

The performance of calix[2]furano[2]pyrrole and related compounds used as neutral carriers for silver selective polymeric membrane electrode was investigated. The silver ion-selective electrode based on calix[2]furano[2]pyrroles gave a good Nernstian response of 57.1 mV per decade for silver ion in the activity range 1×10−6 to 1×10−2 M. The present silver ion-selective electrode displayed very good selectivity for Ag+ ion against alkali and alkaline earth metal ions, NH4+, and H+. In particular, the present Ag+-selective electrode exhibited very low responses towards Hg2+ and Pb2+ ions. The potentiometric selectivity coefficients of the silver ion-selective electrode exhibited a strong dependence on the solution pH. In particular, the response of the electrode to the Hg2+ activity was greatly diminished at pH 2.5 compared to that at pH 5.0. Overall, the performance of the present silver ion-selective electrode based on the ionophore, calix[2]furano[2]pyrrole, is very comparable to that of the electrode prepared with the commercially available neutral carrier in terms of slope, linear range, and detection limits. [Copyright &y& Elsevier]

Abstract: Detection of estrogen, a steroid hormone, has intensively been investigated due to the hormone''s functionalities of estrus arising and carcinogenic elements. More importantly, it is well known that estrogen contamination in environment disturbs the endocrine system in the ecosystem. In this study, the binding reaction between the hormone and its receptor is applied for the detection of estrogen, which enables high selectivity. Moreover, the electrochemical impedance spectroscopy (EIS) method has been employed for a highly sensitive detection in a wide range of concentration. In order to fabricate the electrode covalently bonded with estrogen receptor, the surface modification was firstly done by the molecules including thiol groups and carboxyl groups. It forms self-assembled monolayers (SAMs) with the carboxylic ends in the open side. The cross linkers are involved to form a solid covalent bonding to the estrogen receptor. The interfacial properties of the modified electrodes have been evaluated in the presence of Fe(CN)6 4−/3− redox couple of the probe by EIS. The accumulation of the treated substances on the electrode surface affects the electrochemical behavior of the redox probe. X-ray photoelectron spectroscopy (XPS) provides intermolecular bonding energy to confirm the surface modifications at each step. Estrogen hormone has been successfully detected in 10−6 M concentration. [Copyright &y& Elsevier]