Standard Three-electrode Configuration Research Articles

Tailoring the interface magnetron sputtered silver/tungsten disulfide for battery-supercapacitor hybrids: Electrochemical assessment of redox activity

The emergence of two-dimensional transition metal dichalcogenides as a promising material has attracted significant interest in its potential applications. Also, there is a dire need to explore binder-free routes to fabricate electrodes for enhanced energy storage performance. In this study, tungsten disulfide (WS2) films of varying thicknesses were magnetron sputtered onto nickel foam with silver serving as an interface layer for use in a variety of energy storage applications. Using atomic force microscopy, Raman spectroscopy, X-ray diffraction, and the surface and structural characteristics are explored. The Ag/WS2 electrodes were initially evaluated electrochemically in a standard three-electrode cell configuration to identify the best performing sample. By combining the most superior electrode with activated carbon (AC), a hybrid supercapacitor device (Ag/WS2//AC) was assembled. A maximum energy density of 56.5 Wh kg−1 and 4000 W kg−1 power density was displayed by the hybrid device, with remarkable long-term cyclic stability. Calculating the ‘k’ regression coefficients and separating the capacitive-diffusive current contribution were accomplished using Dunn's model. The superior outcomes of Ag/WS2 may enable their integration into advance energy storage devices of the future.

Electrochemical Characterizations of Ternary MnO2/Cus/Rgo Materials for Supercapacitor Applications

Supercapacitors are considered as a new class of energy storage device because of their high power density, environmentally friendliness, long cycleability, and flexible design capabilities. MnO2 and CuS have been found to be promising for supercapacitor applications because of their low cost, abundance in nature, and are environmentally friendly. Besides this, reduced graphene oxide emerged as most promising carbon materials for energy storage applications because of its high specific surface area, good electrical conductivity, and ability to attach metal oxide withoutany agglomeration. Recently, it has been reported that ternary nanocomposites have superior electrochemical performances because of their synergistic effect, which help to enhance the charge movement within the electrode material. We already reported that the specific capacitance of CuS and MnO2 as 158 F/g and 300 F/g at current densities of 0.5 A/g, respectively [1,2]. In this work we have synthesized MnO2/CuS/rGO ternary nanocomposite by hydrothermal method. The physical characterization of the synthesized materials was carried out using X-Ray diffraction, scanning electron microscopy, differential scanning calorimetry(DSC), and thermogravimetric analysis (TGA). All electrochemical measurements were conducted in standard three-electrode configuration, using a platinum wire, Ag/AgCl, and MnO2/CuS/rGO as a counter, reference, and working electrode, respectively. The results related to physical characterization, specific capacitance, cycleability, and energy density will be presented.Reference: Rahul Singhal, David Thorne, Peter K. LeMaire, Xavier Martinez, Chen Zhao, Ram K. Gupta, David Uhl, Ellen Scanley, Christine C. Broadbridgeand Rakesh K. Sharma, AIP Advances 10, (2020) 035307; https://doi.org/10.1063/1.5132713. Rahul Singhal, Justin Fagnoni, David Thorne, Peter K. LeMaire, Xavier Martinez, Chen Zhao, Ram K. Gupta, David Uhl, Ellen Scanley, Christine C. Broadbridge, Mani Manivannan, MRS Advances, 4 (13) 777-782 (2019), https://doi.org/10.1557/adv.2019.86

(Invited) Agriculture 4.0: Development of Chemical and Biochemical Smart Sensors Systems for Sustainable Food Production

IntroductionWith the global population expected to grow to over 9.6 billion by 2050 it is a projected that a 50-60 % increase in food production will be required. In addition, the increasing wealth of the BRIC (Brazil, Russia, India and China) countries is driving the transition from traditional to more westernized high protein diets. A key challenge then, going forward, will be to close the food gap. This must be achieved against the backdrop of climate change & desertification, labor shortages and competition for energy, land & resources. It is clear then, that addressing this challenge will require the development of more efficient and sustainable food production techniques and processes. Digitizing the entire food chain using smart sensor systems would help enable such an approach. This convergence between the Internet of Things (IoT) and the agri-food industry requires sensor systems and technologies that provide real time data to producers and processers; required for rapid, but informed, decision making. To this end, we are using microelectronic fabrication approaches to develop advanced end-to-end chemical and bio-chemical nanosensor sensor systems specifically tailored to the needs of both producers and processors [1-3]. These sensor systems are being designed to be used by non-specialists and be rugged enough for field deployment [4, 5].Sensor DevelopmentOn-chip devices containing six gold microband electrodes, a gold counter and a platinum pseudo-reference electrodes were fabricated using standard nanofabrication processes on Si/SiO2 substrates as described in detail previously [6]. A custom built Teflon cell permit analysis of small sample volumes (~50 µL), see Fig 1. Gold contact pads were configured on-chip to permit electrical connection to the potentiostat via a microSD port. Chips could be easily plugged in/out enabling rapid analysis of multiple samples. Optical micrographs were acquired using a calibrated microscope (Axioskop II, Carl Zeiss Ltd.) with a charge-coupled detector camera (CCD; DEI-750, Optronics). Electrochemical experiments were carried out using an Autolab Potentiostat/ Galvanostat PGSTAT128N (Metrohm Ltd, Utrecht, The Netherlands) controlled by the Autolab NOVA software. All experiments employed a standard three-electrode cell configuration using a single gold nanoband as the working electrode, versus the on-chip gold counter and platinum pseudo-reference electrodes,. In this study, microband sensors were applied to the detection of Bovine IgG and anti-Fasciola antibodies in serum samples. On-chip microband electrodes were first cleaned using a mixed solvent clean process (acetone, isopropyl alcohol and DI water) for 15 minutes. Cyclic voltammetry was then employed for electropolymerisation of o-aminobenzoic acid (o-ABA, 50 mM in 0.5 M H2SO4) to create a carboxylic terminated polymer layer at the gold electrode surface. A fresh NHS/EDC mixture was prepared in 10 mM acetate buffer, pH 4.0 and subsequently deposited onto the polymerised electrodes, for approximately 30 min, to activate the surface. Concerning IgG, activated electrodes were modified with 1 ng/ml anti-Bovine IgG in 10 mM sodium acetate buffer, pH 4.0 (AB). Anti-IgG was incubated on the electrode for 15 min. Following deposition of these capture biomolecules, unbound active-sites on all electrodes were blocked with ethanolamine (1 M) for 20 minutes. A secondary blocking of 1 % NANNY care® goat based milk in PBS was used for the IgG assay, for a comparison. Results and Conclusions Electrochemical Impedance Spectroscopy (EIS) techniques allows for the monitoring of the increase of the Rct signal and was used to interrogate antigen binding. The reduction of the electron transfer causes an increase in the Rct as seen in Figure 2. Following exposure to igG antibodies an increase in impedance was observed. A semi-logarithmic relationship exists between the concentration of the target and the change in Rct. This correlates with the trend seen in the ELISA calibration plot. The Nyquist plot shows a much larger change in signal between each concentration of Bo IgG than the CV and thus EIS is widely used for evaluating immunosensors such as these.

(Invited) Agriculture 4.0: Development of Chemical and Biochemical Smart Sensors Systems for Sustainable Food Production

Introduction With the global population expected to grow to over 9.6 billion by 2050 it is a projected that a 50-60 % increase in food production will be required. In addition, the increasing wealth of the BRIC (Brazil, Russia, India and China) countries is driving the transition from traditional to more westernized high protein diets. A key challenge then, going forward, will be to close the food gap. This must be achieved against the backdrop of climate change & desertification, labor shortages and competition for energy, land & resources. It is clear then, that addressing this challenge will require the development of more efficient and sustainable food production techniques and processes [1]. Digitizing the entire food chain using smart sensor systems would help enable such an approach. This convergence between the Internet of Things (IoT) and the agri-food industry requires sensor systems and technologies that provide real time data to producers and processers; required for rapid, but informed, decision making. To this end, we are using microelectronic fabrication approaches to develop advanced end-to-end chemical and bio-chemical nanosensor sensor systems specifically tailored to the needs of both producers and processors [2]. These sensor systems are being designed to be used by non-specialists and be rugged enough for field deployment [3]. Sensor Development On-chip devices containing six gold microband electrodes, a gold counter and a platinum pseudo-reference electrodes were fabricated using standard nanofabrication processes on Si/SiO2 substrates as described in detail previously [4]. A custom built Teflon cell permit analysis of small sample volumes (~50 µL), see Fig 1. Gold contact pads were configured on-chip to permit electrical connection to the potentiostat via a microSD port. Chips could be easily plugged in/out enabling rapid analysis of multiple samples. Optical micrographs were acquired using a calibrated microscope (Axioskop II, Carl Zeiss Ltd.) with a charge-coupled detector camera (CCD; DEI-750, Optronics). Electrochemical experiments were carried out using an Autolab Potentiostat/ Galvanostat PGSTAT128N (Metrohm Ltd, Utrecht, The Netherlands) controlled by the Autolab NOVA software. All experiments employed a standard three-electrode cell configuration using a single gold nanoband as the working electrode, versus the on-chip gold counter and platinum pseudo-reference electrodes,. In this study, microband sensors were applied to the detection of Bovine IgG and anti-Fasciola antibodies in serum samples. On-chip microband electrodes were first cleaned using a mixed solvent clean process (acetone, isopropyl alcohol and DI water) for 15 minutes. Cyclic voltammetry was then employed for electropolymerisation of o-aminobenzoic acid (o-ABA, 50 mM in 0.5 M H2SO4) to create a carboxylic terminated polymer layer at the gold electrode surface. A fresh NHS/EDC mixture was prepared in 10 mM acetate buffer, pH 4.0 and subsequently deposited onto the polymerised electrodes, for approximately 30 min, to activate the surface. Concerning IgG, activated electrodes were modified with 1 ng/ml anti-Bovine IgG in 10 mM sodium acetate buffer, pH 4.0 (AB). Anti-IgG was incubated on the electrode for 15 min.. Following deposition of these capture biomolecules, unbound active-sites on all electrodes were blocked with ethanolamine (1 M) for 20 minutes. A secondary blocking of 1 % NANNY care® goat based milk in PBS was used for the IgG assay, for a comparison. Results and Conclusions Electrochemical Impedance Spectroscopy (EIS) techniques allows for the monitoring of the increase of the Rct signal and was used to interrogate antigen binding. The reduction of the electron transfer causes an increase in the Rct as seen in Figure 2. Following exposure to igG antibodies an increase in impedance was observed. A semi-logarithmic relationship exists between the concentration of the target and the change in Rct. This correlates with the trend seen in the ELISA calibration plot. The Nyquist plot shows a much larger change in signal between each concentration of Bo IgG than the CV and thus EIS is widely used for evaluating immunosensors such as these.

Synthesis and characterization of CuS, CuS/graphene oxide nanocomposite for supercapacitor applications

Supercapacitors or electrochemical capacitors are receiving greater interest because of their high-power density, long life, and low maintenance. We have synthesized CuS nanoparticles and graphene oxide (CuS–GO) nanocomposites for supercapacitor applications because of their low cost and excellent electrochemical properties. The phase purity of each material was determined using powder XRD studies. The bandgap was determined by UV-visible spectrophotometric studies. Scanning electron microscope and transmission electron microscope images revealed the nano-scale morphology of the synthesized particles. All the electrochemical measurements were conducted in a standard three-electrode configuration, using a platinum wire as the counter electrode and Hg/HgO as the reference electrode. CuS and its composites with graphene oxide on nickel foam were used as working electrodes. All the electrochemical measurements were performed in 3M KOH solution. The CuS–GO nanocomposite electrode showed a specific capacitance of 250 F/g, 225 F/g, 182 F/g, 166 F/g, 161 F/g, and 158 F/g at a current density of 0.5 A/g, 1 A/g, 5 A/g, 10 A/g, 15 A/g, and 20 A/g, respectively. CuS–GO electrodes showed a specific capacitance retention of 70% after 5000 charge–discharge cycles at a current density of 5 A/g.

Facile synthesis of Mn-doped NiCo2O4nanoparticles with enhanced electrochemical performance for a battery-type supercapacitor electrode

We report the synthesis of manganese-doped nickel cobalt oxide (Mn-doped NiCo2O4) nanoparticles (NPs) by an efficient hydrothermal and subsequent calcination route. The material exhibits a homogeneous distribution of the Mn dopant and a battery-type behavior when tested as a supercapacitor electrode material. Mn-doped NiCo2O4 NPs show an excellent specific capacity of 417 C g-1 at a scan rate of 10 mV s-1 and 204.3 C g-1 at a current density of 1 A g-1 in a standard three-electrode configuration, ca. 152-466% higher than that of pristine NiCo2O4 or MnCo2O4. In addition, Mn-doped NiCo2O4 NPs showed an excellent capacitance retention of 99% after 1000 charge-discharge cycles at a current density of 2 A g-1. The symmetric solid-state supercapacitor device assembled using this material delivered an energy density of 0.87 μW h cm-2 at a power density of 25 μW h cm-2 and 0.39 μW h cm-2 at a high power density of 500 μW h cm-2. The cost-effective synthesis and high electrochemical performance suggest that Mn-doped NiCo2O4 is a promising material for supercapacitors.

(Invited) Nanostructured Photoelectrodes for Unassisted Solar Water Splitting with Enhanced Stability and Surface Catalysts

Nanostructured photoelectrodes with high surface area and tunable optical and electrical properties can potentially benefit a photoelectrochemical (PEC) water splitting system. PEC performance of a nanostructured photoelectrode is usually quantified in a standard three-electrode configuration under potential-assisted conditions because of the additional overpotentials for the two half-reactions of water splitting. However, it is a necessity to fully recognize their potential to split water under unassisted conditions by designing a tandem cell that can provide sufficient voltage to split water. Herein, we present a tandem cell comprised of a photocathode (e.g., carbon-modified cuprous oxide (C/Cu2O) nanoneedles and MoS2-coated Cu2O) and a photoanode (e.g., Co modified BiVO3 and oxygen-deficient titanium dioxide (TiO2−x ) nanorods) for unassisted solar water splitting. The synthesized photoelectrodes were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS) techniques. The tandem cell performance was analyzed by measuring the current-voltage responses in various photoelectrode configurations to validate the collective contributions of both photoelectrodes to unassisted solar water splitting. The PEC properties of these paired photoanodes and photocathodes in a tandem configuration exhibited reasonable photocurrent in the absence of any redox mediator and external bias. Surface active species of photoanode are studied with an ultra-micro electrode of a scanning electrochemical microscope (SECM) to reveal the relationship to substrate and photoexcitation.

Nanocomposites of Copper Sulphide and Graphene Oxide for High-Performance Supercapacitors

Supercapacitors or electrochemical capacitors are receiving greater interest because of their high-power density, long life, low maintenance, and safer operation. The low energy density of such devices needs to improve. In this work, copper sulfide (CuS), a cheap and environment-friendly compound, is used along with graphene oxide (GO) to provide high energy and power densities. CuS nanoparticles and its nanocomposites with GO was synthesized using a facile method for supercapacitor applications. For the synthesis of CuS, an appropriate amount of copper acetate was dissolved in a water-butanol solution for 30 minutes followed by the addition of thiourea. The final solution was then transferred into Teflon-lined stainless-steel autoclave and heated at 180oC for 24 hours. The resulting participate of CuS was recovered using a centrifuge, washed with DI water, and dried in air for 24 hours. A similar procedure was followed for the synthesis of CuS-GO nanocomposite with the addition of appropriate amount of GO in the water-butanol solution prior to the addition of copper acetate and thiourea. Phase purity of the synthesized materials was determined by using X-ray diffraction (XRD) studies. XRD patterns of CuS showed the peaks at 2θ angle of 10.38o, 28.42o, 28.88o, 32.48o, 33.18o, 46.54o, 48.28o, and 59.68o corresponding to (100), (101), (102), (006), (110), (108), (116) planes, respectively, which indicates the covellite CuS hexagonal structure [1,2]. There were no additional peaks found in the XRD pattern of CuS-GO composite, confirming the phase purity of the synthesized materials. TEM images revealed nano-scale morphology of the synthesized particles. The particle size of CuS and CuS/GO composite were found as 95.11 nm, and 64.70 nm, respectively. All the electrochemical measurements were conducted in standard three-electrode configuration, using a platinum wire as a counter electrode and Hg/HgO as a reference electrode. CuS and its composite with graphene oxide on nickel foam were used as working electrodes. All the electrochemical measurements were performed in 3M KOH solution. Electrochemical properties of the synthesized samples were investigated using cyclic voltammetry and galvanostatic charge-discharge studies. The specific capacitance was calculated from cyclic voltammogram, obtained at various scan rate between 10 - 300 mV/s. The specific capacitance of CuS and CuS-GO nanocomposite was found to be 400 and 600 F/g, respectively at a scan rate of 10 mV/s. The detailed results on synthesis, physical, and electrochemical characterization will be presented.

Investigation of enhanced electrochromic properties of α-Fe2O3/RGO nanocomposite thin film prepared by electrodeposition

The α-Fe2O3/reduced graphene oxide (α-Fe2O3/RGO) nanocomposite thin film was prepared by two steps electrodeposition method on the Fluorine doped Tin Oxide (FTO) coated glass substrate. The α-Fe2O3 and α-Fe2O3/RGO nanocomposite films were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The thickness of the nanocomposite film was measured below 400nm.The electrochromic properties of both α-Fe2O3 and α-Fe2O3/RGO nanocomposite films were studied by cyclic voltammetry, chronoamperometry and UV–Vis spectroscopy with the standard three-electrode configuration. The results showed that the α-Fe2O3/RGO thin film have higher optical modulation, faster switching time and better cycling performance compared with pure α-Fe2O3 film. Furthermore, the combination of reduced graphene oxide into iron oxide film enhanced the optical density (ΔOD) about 18% and raised the coloration efficiency (CE) from 18 to 35cm2C−1, at the wavelength of 640nm. The enhanced electrochromic performance is basically attributed to the incorporation of the RGO into α-Fe2O3 film.

BaMF4 (M = Mn, Co, Ni): New electrode materials for hybrid supercapacitor with layered polar structure

To pursuit high electrochemical performance of supercapacitors based on Faradaic charge-transfer with redox reaction or absorption/desorption effect, the intercalation efficiency of electrolyte ions into electrode materials is a crucial prerequisite to surpass the pure surface capacity with extra bulk contribution. Here we report layered barium transition metal fluorides, BaMF4 (M = Mn, Co, Ni) to be a series of new electrode materials applied in standard three-electrode configuration. Benefiting from the efficient immersing of electrolyte ions, these materials own prominent specific capacitance. Electrochemical characterizations demonstrate that all the BaMF4 electrodes show both capacitive behavior and Faradaic redox reactions in the cyclic voltammograms, and ability of charge storage by charging-discharging cycling with high cycling stability. Particularly, BaCoF4 shows the the highest specific capacitance of 360 F g-1 at current density of 0.6 A g-1, even the particle size is far beyond nanometer scale. In addition, first principles calculations reveal the possible underlying mechanisms.

Influence of molybdate ion and pH on the fretting corrosion of a CoCrMo – Titanium alloy couple

Recent findings suggest that during wear CoCrMo alloys develop a protein-rich protective tribochemical film formed by interaction of released molybdate ion with proteins in the lubricant. The purpose of this study was to determine the effect of adding molybdate ions directly to the medium on the fretting corrosion of a high carbon CoCrMo alloy in contact with a Ti6Al4V alloy. We also examined the effect of lowered pH to simulate acidification that may occur in enclosed areas, as within a modular joint.High-carbon CoCrMo cylindrical pins underwent fretting (±50μm, 17N, 60MPa) against a Ti6Al4V rod in a flat-on-cylinder configuration in a custom-designed fretting corrosion set-up that included a standard three-electrode configuration for electrochemical measurements. Four electrolytes were used, consisting of diluted bovine serum (30g/L of proteins), with or without added sodium molybdate (32mM), and at pH4.5 or 7.6. All the tests were performed potentiostatically at −0.25V versus SCE. Total Co, Cr, and Ti release to the media was determined by ICP-MS.The addition of molybdate ion decreased the release of cobalt by 32% and increased the after-to-before ratio of the polarization resistance by 8× at pH4.5, but had not effect on these parameters at pH7.6. Film deposits in the wear scar were more pronounced in the presence of molybdate ion. The addition of molybdate ion to the medium had a significant protective effect for the CoCrMo only at pH4.5, possibly because the lower pH allowed for more molybdate-induced protein film formation.

Classification of vinegar with different marked ages using olfactory sensors and gustatory sensors

An improved classification of vinegar with different marked ages is presented using a combination of gustatory sensors and olfactory sensors. Herein, the gustatory sensor system is developed using four electrodes (gold, copper, platinum and glassy carbon) in a standard three-electrode configuration, and the olfactory system is developed based on a colorimetric sensor array. Initially, the data obtained from the two sensor systems were analyzed separately. Then, the potential of the combination of the two sensor systems for classification is investigated. Principal component analysis (PCA) and linear discriminant analysis (LDA), as two classification tools, are used for data classification. The results show that the capability of discrimination of the combined system is superior to that obtained with the two sensor systems separately, and eventually LDA achieved 100% classification rate by cross-validation. This work indicates that the combination of gustatory sensor systems and olfactory sensor systems can be a useful tool for the classification of vinegar with different marked ages.

Classification of different varieties of Oolong tea using novel artificial sensing tools and data fusion

An improved classification of Oolong tea with different varieties is presented combining two novel artificial sensing tools (i.e. gustatory sensors and olfactory sensors). Herein, the gustatory sensors system was developed by using four electrodes (gold, copper, platinum and glassy carbon) in a standard three-electrode configuration, and the olfactory sensors system was developed based on a colorimetric sensors array. Initially, the data obtained from the two sensor systems was analyzed separately. Then, the potential of the combination of two sensors systems for classification was investigated. Principal component analysis (PCA) and linear discriminant analysis (LDA), as two classification tools, were used for data classification. The results show that the discrimination capability of the combined system is superior to that obtained with the two sensors systems separately, and eventually LDA achieved 100% classification rate by cross-validation. This work indicates that the combination of gustatory sensors system and olfactory sensors system can be a useful tool for the classification of Oolong tea with different varieties.

Temperature effect on water splitting using a Si-doped hematite photoanode

The influence of temperature on the performance of a photoelectrochemical (PEC) cell prepared with Si-doped hematite photoanode was studied for water splitting. The cell performance was characterized by photocurrent-voltage (J–V) characteristic curves and electrochemical impedance spectroscopy at different cell operating temperatures, from 25 °C to 65 °C. A standard three-electrode configuration comprehending the photoelectrode of hematite, the counter-electrode of pure platinum wire (99.9%) and the reference electrode of Ag/AgCl/Sat.KCl was used. The identification of possible degradation pathways was addressed. It was observed that the generated photocurrent density increased with temperature. However, the photoelectrode became unstable above 50 °C. The experiments performed concerning the study of the temperature effect and the aging showed that the optimal operation temperature of the PEC cell is ca. 45 °C; this temperature ensures simultaneously the highest photocurrent density and stability. This study is important for understanding the behavior of hematite photoelectrodes operating under real outdoor conditions.

Synthesis and Electrochromic Characterization of the Graphene/Poly(ethylene oxide)/V2O5·nH2O Ternary Nanocomposite Films

The graphene/poly (ethylene oxide)/V2O5·nH2O films (GPV) were fabricated by sol-gel method. The structure of the ternary nanocomposite films were investigated by X-Ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). V2O5·nH2O layered structure was intercalated by poly (ethylene oxide) (PEO) and graphene. The electrochemical properties of the nanocomposite films were measured by the cyclic voltammetry (CV) and chronoamperometry (CA) measurements with the standard three-electrode configuration. The optical properties were characterized by ultraviolet–visible spectrophotometer. The electrochromic response rate of the GPV films is enhanced evidently. Its bleaching time is 1.8 second, and the coloration time is 3.8 second. These results demonstrate that the GPV films have a potential application in the fast switching electrochromic devices.

Direct mapping of local redox current density on a monolith electrode by laser scanning

An optical method of mapping local redox reaction over a monolith electrode using simple laser scanning is described. As the optical signal is linearly proportional to the maximum redox current that is measured concomitantly by voltammetry, the optical signal quantitatively maps the local redox current density distribution. The method is demonstrated on two types of reactions: (1) a reversible reaction where the redox moieties are ionic, and (2) an irreversible reaction on two different types of enzymes immobilized on the electrode where the reaction moieties are nonionic. To demonstrate the scanning capability, the local redox behavior on a “V-shaped” electrode is studied where the local length scale and, hence, the local current density, is nonuniform. The ability to measure the current density distribution by this method will pave the way for multianalyte analysis on a monolith electrode using a standard three-electrode configuration. The method is called Scanning Electrometer for Electrical Double-layer (SEED).

Detection of Edible Oils Based on Voltammetric Electronic Tongue

A voltammetric electronic tongue to classify five different types of edible oil samples is described in this study. The standard three-electrode configuration composes the sensor array: gold electrode, platinum electrode and saturated calomel electrode. Using cyclic voltammetric measurement, respectively, on five different types of edible oil samples (peanut oil, corn oil, soybean oil, sesame oil and sunflower oil) collected data. The data extracted from the cyclic voltammetry are processed by three algorithms: Principal Component Analysis (PCA), Factor Analysis (FA) and Hierarchical Cluster Analysis (HCA). The result shows that the voltammetric electronic tongue could discriminate all of the five edible oil samples very well.

Synthesis and Electrochromic Characterization of Vanadium Pentoxide/Graphene Nanocomposite Films

The vanadium pentoxide (V2O5)/graphene nanocomposite films have been synthesized by direct intercalation method using V2O5 sol and graphene. The structure of the films was investigated with X-Ray Diffraction (XRD). The electrochemical properties of the nanocomposite films were studied by cyclic voltammetry and chronoamperometry with the standard three-electrode configuration. The optical properties were characterized by UV–Visible spectrophotometer. The intercalation of graphene improves the stability and reversibility of the V2O5 xerogel films. The response rate of the V2O5/graphene nanocomposite films is enhanced. The optical modulatory range of the V2O5/graphene nanocomposite films is 1.5 times larger than that of V2O5 xerogel films. These results demonstrate that the nanocomposite films can be used potentially in fast switching electrochromic devices.

Classification of rice wine according to different marked ages using a portable multi-electrode electronic tongue coupled with multivariate analysis

A developed multi-electrode electronic tongue combined with multivariate analysis was attempted to classify Chinese rice wine according to four different marked ages (3, 5, 8 and 10years) for authentication. The electronic tongue consisted of three working electrodes (glassy carbon, gold and platinum) in a standard three-electrode configuration, using cyclic voltammetry technique to record signals. Characteristic values were extracted from the raw data signals for further multivariate analysis. In developing the discrimination models, linear (SIMCA, PLSDA and KNN) and nonlinear (BPANN and SVM) pattern recognition methods were comparatively employed, and they were optimized by cross-validation. Compared with other models, BPANN model achieved the best result, with the identification rate of 100% in the calibration set, and 100% in the prediction set. The overall results showed that this portable multi-electrode electronic tongue system with BPANN classification tool could successfully be used in identification of rice wine with different marked ages.

Multilayered Thin Metal Film Deposition by Sequential Operation of Nanosilicon Electron Emitter in Metal–Salt Solutions

The use of a nanocrystalline silicon (nc-Si) ballistic electron emitter in metal–salt solutions induces the deposition of thin metal films. The nc-Si emitter is composed of a thin Au/Ti film, an anodized polycrystalline Si layer, and an n+-Si substrate. When the emitter is driven in NiCl2, CoSO4, and ZnSO4 solutions without using any counter electrodes, thin Ni, Co, and Zn films are deposited on the emission area, respectively, as well as a thin Cu film in CuSO4 solution. According to cyclic voltammogram measurements under a standard three-electrode configuration, the hot electron injection effect into the solution is clearly observed in all cases at potentials within the electrochemical window, in which no electrolytic reactions occur. Energetic electrons injected into the solutions cause the direct reduction of metal ions. As a possible application, the multilayered deposition of different metals is demonstrated by sequential operation in NiCl2 and CuSO4 solutions.