Three-layer Electrode Research Articles

The Novel Three-Layer Electrode Based on Poly(Neutral Red) for Potentiometric Determination of Citrates

The three-layer electrode consisting of the inner, middle, and outer layers of polythiophene (PTh), polyaniline (PANI), and poly(neutral red) (PNR), respectively, was developed, characterized, and tested as a potentiometric sensor for citrates. The spectroscopic and morphological findings based on Raman spectroscopy and scanning electron microscopy, respectively, demonstrated the consecutive formation of individual polymeric layers derived from PTh, PANI, and PNR in the multilayer system. The sharper and narrower peak profiles of PNR in the case of the three-layer system revealed a more organized structure than for the PNR layer alone. The PNR layer in such a novel arrangement shows the highest selectivity towards citrates among the tested carboxylates. Simultaneously, the unwanted influence of the underlying Pt surface is eliminated. The potentiometric characteristics of the proposed potentiometric sensor were examined at the detection of citrates in the real-world samples, compared with results for PNR simple electrode, and corresponded with the reference capillary electrophoresis and literature-based spectrophotometric method.

A high-performance Ni-CeO2/Ni/Ni-Y2O3·ZrO2 three-layer anode for direct iso-octane feeding of solid oxide fuel cells.

Solid oxide fuel cells (SOFCs) directly fed with iso-octane are expected to be power sources for mobile devices and automobiles. However, the conventional anode catalysts nickel (Ni) or cerium oxide (CeO2) used for direct feeding of iso-octane do not suppress carbon deposition or generate high power. In this study, we investigated the Ni-CeO2/Ni/Ni-yttria-stabilized-zirconia (YSZ) three-layer anode to establish the suppression of carbon deposition and high-power generation in the SOFC. The anode consists of a Ni-CeO2 catalyst layer as the top layer, an Ni catalyst layer as the second layer, and a Ni-YSZ catalyst layer as the third layer on top of the electrolyte. The concept of the three-layer anode is as follows: fuel reforming occurs in the Ni-CeO2 layer, the reformed H2 or CO is electrochemically oxidized in the Ni-YSZ catalyst layer, and the Ni catalyst middle layer prevents the reaction between YSZ and CeO2. Scanning electron microscopy and electrochemical characterization confirmed carbon deposition suppression and improved power generation. The anode showed no carbon deposition and generated high-power, 600 mA cm−2 and 150 mW cm−2, at 950°C and a steam/carbon ratio of 3.0. Additionally, we discuss the fuel reforming reactions on the three-layer electrode by the results of exhaust gas analysis.

Back-Channel-Etched IGZO TFTs With Cu-Based Multilayer Electrodes Using MoAl Alloy and MoMn Alloy as Buffer Layers

We report high-performance IGZO TFTs with MoAl/Cu/MoAl and MoMn/Cu/MoMn three-layer electrodes, where MoAl or MoMn alloy is used as the buffer layer. The multilayer electrode has good electrical properties and can effectively prevent the oxidation and diffusion of the middle Cu layer. In addition, the multilayer electrode can be etched in a PAN etchant solution and match the etching rate with Cu. Based on these MoAl/Cu/MoAl and MoMn/Cu/MoMn electrodes, vacuum-processed IGZO TFTs exhibit a turn-on voltage of 0 V, an on-off ratio of 10⁹, and a mobility of 10.7 cm² V⁻¹ s⁻¹ after annealing at 115 °C in N₂. Under the gate bias stress test, devices with MoMn electrodes, which exhibit a small threshold voltage shift, show better performance than those with MoAl electrodes. The presented studies may provide another option for the Cu buffer layer.

Spectroscopic ellipsometry to precisely estimate the thickness for optimizing the performance of three-layer broadband transparent electrodes

This work utilized the optical properties of indium tin oxide/silver/indium tin oxide electrodes to set up the fitting range for spectroscopic ellipsometry (SE) analysis. Then, the SE fitting on the thickness and optical constants of each layer in several separate stages was investigated. In this way, the results suggest that the SE fitting can be able to converge rapidly and obtain the precise thickness of each layer. Experiment analysis shows that when the silver layer thickness was 8.5–11.5 nm, the sheet resistance of the uniform electrodes was 82.0% in the visible light region; the related Haacke indexes were > 22.0 × 10−3 Ω−1. For photovoltaic application, when the silver layer thickness was 7.5–8.5 nm, the sheet resistance of the three-layer electrodes was 77.5%; the related Haacke indexes were > 9.0 × 10−3 Ω−1. Comparing the SE results with experimental measurements, it is concluded that the uniformity of the silver layer and the stability of the sputtering system were the major factors affecting the optoelectronic performance of the three-layer electrodes.

An Active Concentric Electrode for Concurrent EEG Recording and Body-Coupled Communication (BCC) Data Transmission.

This paper presents a wearable active concentric electrode for concurrent EEG monitoring and Body-Coupled Communication (BCC) data transmission. A three-layer concentric electrode eliminates the usage of wires. A common mode averaging unit (CMAU) is proposed to cancel not only the continuous common-mode interference (CMI) but also the instantaneous CMI of up to 51Vpp. The localized potential matching technique removes the ground electrode. An open-loop programmable gain amplifier (OPPGA) with the pseudo-resistor-based RC-divider block is presented to save the silicon area. The presented work is the first reported so far to achieve the concurrent EEG signal recording and BCC-based data transmission. The proposed chip achieves 100dB CMRR and 110dB PSRR, occupies 0.044 mm2, and consumes 7.4μW with an input-referred noise density of 26nV/√Hz.

CRP-binding bacteriophage as a new element of layer-by-layer assembly carbon nanofiber modified electrodes

Recently, bacteriophage particles have started to be applied as a new biomaterial for developing sensing platforms. They can be used as both a recognition element or/and as building blocks, template/scaffold. In this paper, we studied a bacteriophage selected through phage-display technology. The chosen bacteriophage acted as a building block for creating a carbon nanofiber-based electrode and as a new receptor/binding element that recognizes C-reactive protein (CRP) – one of the markers of inflammatory processes in the human body. The binding efficiency of the selected phage towards CRP is two orders of magnitude higher than in the wild type. We demonstrate that the phage-based sensor is selective against other proteins. Finally, we show that layer-by-layer methods are suitable for deposition of negatively charged phages (wild or CRP-binding) with positively charged carbon nanofibers for electrode surface modification. A three-layered electrode was successfully used for molecular recognition of CRP, and the molecular interactions were studied using electrochemical, biological, and optical methods, including microscopic and spectroscopic analyses.

Electrochemical performance of a three-layer electrode based on Bi nanoparticles, multi-walled carbon nanotube composites for simultaneous Hg(II) and Cu(II) detection

Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals. This article proposes a novel composite electrode based on a polyaniline (PANi) framework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nanotubes (Bi NPs@GO-MWCNTs) for the simultaneous detection of multiple heavy metal ions. Composite electrodes are prepared on screen-printed electrodes (SPCEs) using an efficient dispensing technique. We used a SM200SX-3A dispenser to load a laboratory-specific ink with optimized viscosity and adhesion to draw a pattern on the work area. The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology. Electrochemical techniques, such as cyclic voltammetry and differential pulse voltammetry, were used to demonstrate the sensing capabilities of the proposed sensor. The sensitivity, limit of detection, and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×102 μA L μmol−1 cm−2, 0.01 nmol/L, and 0.01 nmol/L–5 mmol/L and 0.15×10−1 μA L μmol−1 cm−2, 0.5 nmol/L, and 0.5 nmol/L–5 mmol/L for mercury ion (Hg(II)) and copper ion (Cu(II)) detection, respectively. In addition, the electrode exhibits a good selectivity and repeatability for Hg(II) and Cu(II) sensing when tested in a complex heavy metal ion solution. The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected. Therefore, the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.

Characterization of Calcium Ion Release from a Polymer-Coated Electrode with a Plasticized PVC Membrane Containing Calcium Salts, and Its Contraction Examination of Vorticella Convallaria

Abstract Up to now several bio-imaging methods have taken very good pictures and/or recordings. With bio-imaging growing, a micro-stimulation method to limit in a fine region is required. Conventional chemical stimulation methods face difficulty in fulfilling this requirement, however, an electrochemical device is a potential response to this issue. This paper reports on the fabrication and the use of an electrochemical Ca2+-releasing device. The device consists of a three-layer electrode, including two transducers, a PVC membrane, PEDOT layer, and gold or carbon. The dynamic behavior of Ca2+ released from the device is evaluated by a two-dimensional 16 K pixel array Ca2+ image sensor, and is simulated using a diffusion model of Ca2+. Both experimental and calculated time and distance dependent profiles are almost in agreement when the PVC membrane is thin. As its biological application, a permeabilized Vorticella convallaria was set at a distance of ca. 0.1 mm from the Ca2+-releasing device. There was no response for some time just after switching-on, and then it gradually contracted. The gradual contraction after the interval proved that the Ca2+-releasing device can be used as a soft insertion based on the concentration diffusion.

Sacrificial layer-assisted one-step transfer printing for fabricating a three-layer dry electrode

A sacrificial-layer assisted one-step transfer printing method is presented to fabricate a three-layer dry electrode for detecting electrophysiological signals. First, an Au electrode layer was deposited on a silicon wafer covered by a Cu sacrificial layer. Then, a polyimide (PI) intermediate layer was patterned on the Au layer by a standard photolithography process, and subsequently the Au layer was patterned by wet etching, using the patterned PI layer as the etching mask. Finally, both the patterned Au layer and PI layer were transferred onto a stretchable film in one step to make a three-layer dry electrode by etching away the Cu sacrificial layer. This three-layer dry electrode exhibited excellent conformability and stretchability and low electrode-skin contact impedance. The performance of the three-layer dry electrode for long-term and dynamic electrocardiogram (ECG) monitoring was also examined. The quality of ECG signals was well maintained for 48 h, during which period the signal to noise ratio was kept at 40 dB. It was also found that the physical exercises had only slight effects on the ECG signal, where all features of the signal were clearly distinguishable when the volunteer ran at 5 km/h.

Finger Displacement Sensing: FEM Simulation and Model Prediction of a Three-Layer Electrode Design

There is a growing and significant interest in home-based therapy or telerehabilitation for physiological disabilities, for example, as a result of stroke. These technologies allow more flexibility in implementing rehabilitation sessions and offer the potential to reduce the economic burden of outpatient appointments and reduce the reliance on healthcare systems. However, extra effort needs to be made to make such systems effective. This paper investigates the feasibility of a home-based device, which is capable of detecting minute movements of patients’ fingers in regular training and testing sessions, addressing ease of use, motivation of practice, as well as feedback and guidance on performance. Toward this aim, the measuring techniques that are compatible with these targets were investigated. Based on a customizable three-layer electrodes design for use with an MGC3030 motion sensor IC, a finite-element method simulation in COMSOL Multiphysics and a nonlinear regression analysis using MATLAB were carried out. Four nonlinear equations were introduced to describe the motion of the index and middle fingers in the electrical field (E-field) generated. The form of the prediction models agrees with the hypothesis based on the quasi-static E-field sensing theory. In addition, these prediction models fit well with the relationship between finger distance and the voltage signals detected. With the prediction model, the targeted system is capable of detecting combined movements of two fingers at a resolution of 0.94 mm in a portable smart device for robust hand rehabilitation.

Behavior of Al/Cu/Ti electrodes in surface acoustic wave filter at high power

Driven by the need for high data-rates and continuous reduction in device size, surface acoustic wave filters are required to work under increasingly high power. In this work, a series of 2.7 GHz surface acoustic wave filters with Al/Cu/Ti three-layered electrode were fabricated and loaded with high power. Those three-layered electrodes showed weaker texture but higher stability than Al-Cu alloy electrode at high power. Morphologies, microstructures and elements distribution in cross section of fingers were analyzed carefully before and after high power loading. Results show that the circular-arc-shaped outline of fingers were appeared in most samples after high power loading, and the number of gains in the finger cross section changed from some into several with much larger volume. The features of distribution of Cu atoms also coincided with these microstructures. By finite element method and phase diagram analysis, the higher stability of Al/Cu/Ti three-layered electrodes are attributed to precipitation of θ-CuAl2 in the bottom edge of electrode finger and Cu-doped α-Al in the center top.

A multilayer gold nanoparticle-polydopamine hybrid membrane-modified indium tin oxide electrode for selective sensing of dopamine in the present of ascorbic acid

In this paper, dopamine (DA) ionic states in different pH solutions and corresponding electrochemical reaction characteristics on indium tin oxide (ITO) electrodes were discussed in detail. Polydopamine (PDA) and gold nanoparticles (AuNPs) have been used to modify ITO electrodes for selective sensing of DA in the present of ascorbic acid (AA). The impedance of PDA membranes and the catalysis of AuNPs on the interfacial properties of the modified electrodes were studied tentatively. Experiments show that a three-layer AuNP-PDA hybrid membrane-modified ITO electrode has an excellent property in DA detection without being interfered by the existence of AA. The sensitivity of DA detection was obtained to be 0.300 μA/μM with a detection limit of 0.06 μM (S/N = 3) in chronoamperometry measurement. The application of the electrode was verified in real sample analysis with both differential pulse voltammetry and chronoamperometry measurements.

Corrosion Behavior and Metallization of Cu-Based Electrodes Using MoNi Alloy and Multilayer Structure for Back-Channel-Etched Oxide Thin-Film Transistor Circuit Integration

Mo/Cu bilayer is the most conventional metal electrode with an excellent electrical conductivity and high environmental resistance for large-area back-channel-etch amorphous oxide thin-film transistors (TFTs) circuit integration. However, the Mo/Cu bilayer is metallized with a poor etch profile in conventional weak acidic H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based etchant solution. This is attributed to the formation of Mo-related oxide residue and a high etch rate ratio between Mo and Cu, which results in short circuit and electrical degradation in the following microscale metallization and induces electrical instability on oxide TFT. We have replaced Mo with a MoNi (Mo:Ni = 1:3) alloy that has a larger galvanic potential difference in Cu-Ni (E° <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cu-Ni</sub> : 0.597 V > E° <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cu-Mo</sub> : 0.492 V) and seldom induces metal oxide residues in conventional etchants. In addition, an alternative three-electrode structure (MoNi/Cu/MoNi) was proposed to suppress Cu ionization by offering sufficient galvanic current from top and bottom MoNi layers. As a result, this MoNi/Cu/MoNi exhibits a wet-etched morphology with a rectangular profile, optimal taper angle, and less CD loss, which allows the formation of microscale metal linewidth. Furthermore, the application of MoNi/Cu/MoNi three-layer electrode in TFTs leads to more reliable electrical performance and good uniformity.

Simulation research on gastric emptying measurement experiment by electrical impedance tomography with three-layer electrodes

Objective To verify the effectiveness of electrical impedance tomography (EIT) with multi-layer electrodes in gastric emptying measurement by simulation experiments using EIT with three-layer electrodes. Methods Firstly, EIT system with three-layer electrodes and gastric emptying measurement simulation equipment was designed and constructed to simulate gastric emptying process and obtain EIT reconstruction images. Secondly, the region where the electrical characteristic of gastric changes was selected as region of interest. Finally, the relative impedance change rate in region of interest for every image obtained from all three layers was consecutively recorded, then the gastric emptying curve was formed and gastric emptying time was calculated. Results There are obvious differences among the sharp of impedance change curves of interested region for three layers, and the gastric emptying time and process of each layer is also different from one another. It is suggested that the passing path and emptying manner of food in gastric emptying process reflected by EIT images varied from layer to layer. Therefore, the necessity and feasibility of using EIT with three-layer electrodes in gastric emptying measurement study is verified. Conclusions EIT with three-layer electrodes can provide more abundant information of gastric motility function associated with gastric emptying pathology and physiology state. It is likely to be a noninvasive, convenient and effective imaging method for the detection and evaluation research on gastric emptying and gastric motility. Key words: Electrical impedance tomography; Three-layer imaging; Gastric emptying; Simulation experiments

Graphene oxide/graphene vertical heterostructure electrodes for highly efficient and flexible organic light emitting diodes.

The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability, and good compatibility with HIL materials (MoO3 in this work). Moreover, the conductivity of the heterostructure is not sacrificed compared to the pristine three-layer graphene electrodes, but is significantly higher than that of pristine two-layer graphene films. In addition to high flexibility, OLEDs with different emission colors based on the GO/G heterostructure TCEs show much better performance than those based on indium tin oxide (ITO) anodes. Green OLEDs with GO/G heterostructure electrodes have the maximum current efficiency and power efficiency, as high as 82.0 cd A(-1) and 98.2 lm W(-1), respectively, which are 36.7% (14.8%) and 59.2% (15.0%) higher than those with pristine graphene (ITO) anodes. These findings open up the possibility of using graphene for next generation high-performance flexible and wearable optoelectronics with high stability.

Flexible electrochromic films based on CVD-graphene electrodes

Graphene synthesized via chemical vapor deposition is a notable candidate for flexible large-area transparent electrodes due to its great physical properties and its 2D activated surface area. Electrochromic devices in optical displays, smart windows, etc are suitable applications for graphene when used as a transparent conductive electrode. In this study, various-layer graphene was synthesized via chemical vapor deposition, and inorganic WOx was deposited on the layers, which have advantageous columnar structures and W6+ and W4+ oxidation states. The characteristics of graphene and WOx were verified using optical transmittance, Raman spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy. The optimum transparent conductive electrode condition for controlling graphene layers was investigated based on the optical density and cyclic voltammetry. Electrochromic devices were fabricated using a three-layer graphene electrode, which had the best optical density. The graphene in the flexible electrochromic device demonstrated a potential for replacing ITO in flexible electronics.

Preparation of the working electrode of dye-sensitized solar cells: Effects of screen printing parameters

The working electrode films of dye-sensitized solar cells are screen printed using a stainless steel cloth screen or a stencil screen. The as-prepared films and the corresponding cells are characterized and evaluated. The films prepared using the stainless steel cloth screen are thinner than those prepared using the stencil screen under the same screen printing conditions. Thus, while the stainless steel cloth screen is suitable for multi-layer film preparations, the stencil screen is ideal for mono-layer film preparations. Provided that the total working electrode film thickness is about the same, a three-layer working electrode prepared using the stainless steel cloth screen gives a cell with the conversion efficiency of 5.46% and a mono-layer working electrode prepared using the stencil screen gives a cell with the conversion efficiency of 5.30%. When using the stainless steel cloth screen for the working electrode preparation, a low squeegee angle and a low printing speed gives a porous thick film, which is ideal for dye absorption.

Improving electrochemical performances of LiFePO4/C cathode material via a novel three-layer electrode

As an improvement on the conventional two-layer electrode (active material layer|current collector), a novel sandwich-like three-layer electrode (conductive layer|active material layer|current collector) for cathode material LiFePO4/C was introduced in order to improve its electrochemical performance. LiFePO4/C in the three-layer electrode exhibited superior rate capability in comparison with that in the two-layer electrode in accordance with charge-discharge examination. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that Fe3+/Fe2+ redox couple for LiFePO4 in the three-layer electrode displayed faster kinetics, better reversibility and much lower charge transfer resistance than that in the two-layer electrode in electrochemical process. For three-layer electrode, the holes in the surface of active material layer were filled by smaller acetylene black grains, which formed electrical connections and provided more pathways to electron transport to/from LiFePO4/C particles exposed to the bulk electrolyte.

Homogeneous-aligned high-transmission and fast-response liquid crystal display with three-layer electrodes

A homogeneous-aligned, high-transmission, and fast-response liquid crystal display (LCD) with three-layer electrodes is proposed. The molecules of liquid crystals are more inclined to rotate above and between the pixel electrodes. This induces a much higher transmission than that of the cell driven by the fringe field switching method and a wide viewing angle simultaneously because of the combined fringe and in-plane electric fields. Furthermore, a trigger pulse voltage is applied between the top and common electrodes to forcibly align the liquid crystal molecules vertically to show the transient dark state, which results in a very fast turn-off time (>>1 ms). With high degree of transmission and fast response time, this kind of LCD is a potential candidate for large LCD panels.

Modeling of multilayer electrode performance in transverse electro-optic modulators

For some electro-optic (EO) modulators, lowering the driving voltage is necessary to reduce the power consumption of the modulators. There are four significant factors influencing the driving voltage of the EO modulators: geometrical parameters of wafer and electrodes, surface and embedded electrodes, material properties of wafer, and structure of modulators. Using the superposition method and surface charge technique, the electric fields, halfwave voltages, switching times and optical transmissions of EO modulators with two-layer, three-layer, and four-layer electrodes are calculated, respectively. It is found that the halfwave voltage decreases while the switching time increase slightly as the number of layers increases. Such study demonstrates that using multilayer electrodes is an effective technique of lowering the halfwave voltage, which may have implication of EO modulator design.