Platinum Black Electrodes Research Articles

Deconvolution of Cyclic Voltammograms in the Hydrogen Region of the Platinum-Black Electrodes with the Asymmetric Double Sigmoid Function

Deconvolution of Cyclic Voltammograms in the Hydrogen Region of the Platinum-Black Electrodes with the Asymmetric Double Sigmoid Function

Electrolytic conductivity measurements for ten ionic liquids

Electrolytic conductivity measurements for a total of ten ionic liquids (ILs) (four N-alkyl-N-methyl pyrrolidinium cations [Cnmpyr] and six 1-(methyl)benzyl-3-alkyl imidazolium cations ([Bnmim] or [MeBnCnmim]), all paired with bistriflimide [Tf2N] anions) are reported at p = 0.1 MPa over T = 293.15 – 323.15 K. All samples were thoroughly dried under vacuum and their water content before and after measurements was determined by Karl Fischer titration. For the conductivity measurements, an impedance bridge technique was used in conjunction with a sealed cell equipped with platinum black electrodes. The cell constant (Kcell = 101 m − 1) was determined with standard aqueous KCl solutions before and after measurements. The results show that electrolytic conductivity increases with increasing temperature in both families of ILs, while conductivity decreases as the length of the IL side chain increases, which is associated with increase in IL viscosity. Conductivities of the pyrrolidinium ILs were consistent with other data for these compounds already reported in the literature. The conductivities of the 1-(methyl)benzyl-3-alkyl imidazolium ILs are reduced by ∼70-90% compared to the analogous 1-alkyl-3-methylimidazolium ILs

Evaluation of Activated Carbon and Platinum Black as High-Capacitance Materials for Platinum Electrodes

The application of direct current (DC) produces a rapid and reversible nerve conduction block. However, prolonged injection of charge through a smooth platinum electrode has been found to cause damage to nervous tissue. This damage can be mitigated by incorporating high-capacitance materials (HCM) (e.g., activated carbon or platinum black) into electrode designs. HCMs increase the storage charge capacity (i.e., “Q value”) of capacitive devices. However, consecutive use of these HCM electrodes degrades their surface. This paper evaluates activated carbon and platinum black (PtB) electrode designs in vitro to determine the design parameters which improve surface stability of the HCMs. Electrode designs with activated carbon and PtB concentrations were stressed using soak, bend and vibration testing to simulate destructive in vivo environments. A Q value decrease represented the decreased stability of the electrode–HCM interface. Soak test results supported the long-term Q value stabilization (mean = 44.3 days) of HCM electrodes, and both HCMs displayed unique Q value changes in response to soaking. HCM material choices, Carbon Ink volume, and application of Nafion™ affected an electrode’s ability to resist Q value degradation. These results will contribute to future developments of HCM electrodes designed for extended DC application for in vivo nerve conduction block.

A long-term stable and flexible glucose sensor coated with poly(ethylene glycol)-modified polyurethane

• A flexible glucose sensor with long service life and good consistency is proposed. • GOx is coated on the electrode surface by a self-developed electrospray apparatus. • PU surface is modified by chemical grafting to improve its biocompatibility. Flexible biosensors have the great potential to be applied in medical diagnosis, wearable devices, fermentation and other fields. This paper proposes a manufacturing scheme of a flexible enzymatic glucose sensor coated with polyurethane modified by poly(ethylene glycol), PU-PEG, as a protective membrane, which can overcome the problems of poor consistency and short service life of the electrochemical sensor. A platinum-black electrode formed by electroplating platinum-black nanoparticles onto a flexible gold electrode is used as an enzyme carrier. The enzyme is electrosprayed evenly onto the electrode to avoid aggregation and to control quality. Glutaraldehyde is used as a cross-linking agent to immobilise the enzyme layer. Additionally, using PU-PEG as the protective membrane improves the anti-interference performance, controls the enzymatic reaction rate and makes long-term stable operation of the sensor possible. The experimental results show that the linear range of the sensor is 0.5 ~ 25 mM, the minimum detection limit is 0.25 mM, and the sensitivity is as high as 3.418 μA/mM. The measurement results of the sensors show good consistency, with a maximum absolute deviation of only 5.52%. The effective working time in 37℃ bovine serum with a glucose concentration of 5 mM is up to 23 days.

Effect of oxygen terminated surface of boron-doped diamond thin-film electrode on seawater salinity sensing

Tremendous demands for highly sensitive and stable seawater salinometers have motivated intensive research on advanced electrode materials. Boron-doped diamond (BDD) is attractive in terms of its high mechanical stability and chemical inertness, but is usually hindered by its low double-layer capacitance (Cdl) for seawater salinity detection. Here, inspired by the principle of oxygen-terminated BDD electrode endowing higher Cdl than hydrogen-terminated surface, we introduce the oxygen terminated surface by oxygen plasma or reactive ion etch (RIE), and the fabricated oxygen terminated BDD electrodes demonstrate high sensitivity and long-term stability in seawater salinity detection comparing with the hydrogen terminated BDD electrodes. Significantly, the as-fabricated O-BDD-RIE electrodes not only show remarkable enhanced response even better than the commercial platinum black electrodes but also display long-time stability which is weekly verified by continuous monitor for 90 days. The outstanding performance of the oxygen terminated BDD electrodes can be ascribed to the enhancement of C-O surface functional group on Cdl. In addition, a comprehensive analysis of effective electroactive surface area (EASA) and Cdl proves that the surface oxygen is the major factor for the improved Cdl. In summary, the excellent oxygen terminated BDD electrodes promise potential application in seawater salinity detection.

Chemically synthesized Bi2S3, CuS and Bi2S3/CuS heterostructure materials as counter electrode: Dye sensitized solar cell application

In the present work, we have successfully synthesized Bi2S3, CuS, and its heterojunction Bi2S3/CuS thin film on fluorine doped tin oxide (FTO) coated glass as counter electrodes. These depositions are done by simple, cost effective, and simply executable sequential chemical bath deposition (S-CBD) method. Well optimized preparative parameters led to the formation of good quality thin films of Bi2S3 and CuS films and heterojunction. The structural validation Bi2S3, CuS, and its heterojunction were achieved by X-ray diffraction and Raman scattering, surface morphological study observed through Scanning Electron Microscopy (SEM) and topology was confirmed by Atomic Force Microscopy (AFM). We have employed Bi2S3/CuS heterostructure as a counter electrode (CE) in dye-sensitized solar cell (DSSC). We have observed different parameters like short circuit current density (Jsc), open circuit voltage (Voc), Fill Factor (FF) and efficiency (n) by Current–voltage (J-V) characteristics. Though we do not achieve an anticipated outcome for heterostructure compared with conventional Platinum and Carbon black counter electrode, CuS separately found worthy as Counter electrode (CE) in DSSC.

Nanostructured boron-doped diamond electrode for seawater salinity detection

Electrodes with high response and stability are urgently required to reach a steady and accurate measurement of seawater salinity. Herein, boron-doped diamond (BDD) is for the first time considered as a promising alternative to commercial platinum black in seawater salinity detection due to their considerable conductivity and outstanding stability. However, the intrinsical low double layer capacitance (DLC) of planar BDD film (BDDF) electrodes affect their response in the detection. To solve these problems, boron-doped diamond nanorod forest (BDDNF) electrodes are fabricated via hot filament chemical vapor deposition. Noted, four orders of magnitude larger of DLC (2820 μF/cm2) than BDDF (0.35 μF/cm2) is achieved on BDDNF due to a much enhanced electroactive surface area which is calculated to be 1.47 times larger than BDDF. Benefited from the enhanced DLC and accelerating diffusion resulted by the nanostructure, the response of BDDNF exhibits an enhancement by a factor of 1.5 compared to BDDF at the salinity of 40 ‰. Moreover, in striking contrast to commercial platinum black electrode, the obtained BDDNF electrodes exhibit outstanding stability thanks to the increased amount of carbon oxygen functional groups on BDDNF surface. This work greatly promises the potential applications of BDDNF electrodes in seawater salinity detection.

A nanoelectrode array for obtaining intracellular recordings from thousands of connected neurons

Current electrophysiological or optical techniques cannot reliably perform simultaneous intracellular recordings from more than a few tens of neurons. Here, we report a nanoelectrode array that can simultaneously obtain intracellular recordings from thousands of connected mammalian neurons in vitro. The array consists of 4,096 platinum-black electrodes with nanoscale roughness fabricated on top of a silicon chip that monolithically integrates 4,096 microscale amplifiers, configurable into pseudo-current-clamp mode (for concurrent current injection and voltage recording) or into pseudo-voltage-clamp mode (for concurrent voltage application and current recording). We used the array in pseudo-voltage-clamp mode to measure the effects of drugs on ion-channel currents. In pseudo-current-clamp mode, the array recorded intracellular action potentials and post-synaptic potentials from over thousands of neurons. In addition, we mapped over 300 excitatory and inhibitory synaptic connections from over 1,700 neurons that were recorded for 19 mins. This high-throughput intracellular-recording technology could benefit functional connectome mapping, electrophysiological screening, and other functional interrogations of neuronal networks.

Optimization of a microchip electrophoresis method with electrochemical detection for the determination of nitrite in macrophage cells as an indicator of nitric oxide production.

Nitric oxide (NO) is involved in many biological functions, including blood pressure regulation, the immune response, and neurotransmission. However, excess production of NO can lead to the generation of reactive nitrogen species and nitrosative stress and has been linked to several neurodegenerative diseases and cardiovascular disorders. Because NO is short-lived and generally difficult to detect, its primary stable degradation product, nitrite, is frequently monitored in its place. In this paper, an improved method using microchip electrophoresis with electrochemical detection (ME-EC) was developed for the separation and detection of nitrite in cell lysates. A separation of nitrite from several electroactive cell constituents and interferences was optimized, and the effect of sample and buffer conductivity on peak efficiency was explored. It was found that the addition of 10 mM NaCl to the run buffer caused stacking of the nitrite peak and improved limits of detection. A platinum black working electrode was also evaluated for the detection of nitrite and other electroactive cellular species after electrophoretic separation. The use of a modified platinum working electrode resulted in 2.5-, 1.7-, and 7.2-fold signal enhancement for nitrite, ascorbic acid, and hydrogen peroxide, respectively, and increased the sensitivity of the method for nitrite twofold. The optimized ME-EC method was used to compare nitrite production by native and lipopolysaccharide-stimulated RAW 264.7 macrophage cells.

Quantification of Signal-to-Noise Ratio in Cerebral Cortex Recordings Using Flexible MEAs With Co-localized Platinum Black, Carbon Nanotubes, and Gold Electrodes.

Developing new standardized tools to characterize brain recording devices is critical to evaluate neural probes and for translation to clinical use. The signal-to-noise ratio (SNR) measurement is the gold standard for quantifying the performance of brain recording devices. Given the drawbacks with the SNR measure, our first objective was to devise a new method to calculate the SNR of neural signals to distinguish signal from noise. Our second objective was to apply this new SNR method to evaluate electrodes of three different materials (platinum black, Pt; carbon nanotubes, CNTs; and gold, Au) co-localized in tritrodes to record from the same cortical area using specifically designed multielectrode arrays. Hence, we devised an approach to calculate SNR at different frequencies based on the features of cortical slow oscillations (SO). Since SO consist in the alternation of silent periods (Down states) and active periods (Up states) of neuronal activity, we used these as noise and signal, respectively. The spectral SNR was computed as the power spectral density (PSD) of Up states (signal) divided by the PSD of Down states (noise). We found that Pt and CNTs electrodes have better recording performance than Au electrodes for the explored frequency range (5–1500 Hz). Together with two proposed SNR estimators for the lower and upper frequency limits, these results substantiate our SNR calculation at different frequency bands. Our results provide a new validated SNR measure that provides rich information of the performance of recording devices at different brain activity frequency bands (<1500 Hz).

Towards non-invasive characterisation of coronary stent re-endothelialisation – An in-vitro, electrical impedance study

The permanent implantation of a stent has become the most common method for ameliorating coronary artery narrowing arising from atherosclerosis. Following the procedure, optimal arterial wall healing is characterised by the complete regrowth of an Endothelial Cell monolayer over the exposed stent surface and surrounding tissue, thereby reducing the risk of thrombosis. However, excessive proliferation of Smooth Muscle Cells, within the artery wall can lead to unwanted renarrowing of the vessel lumen. Current imaging techniques are unable to adequately identify re-endothelialisation, and it has previously been reported that the stent itself could be used as an electrode in combination with electrical impedance spectroscopic techniques to monitor the post-stenting recovery phase. The utility of such a device will be determined by its ability to characterise between vascular cell types. Here we present in-vitro impedance spectroscopy measurements of pulmonary artery porcine Endothelial Cells, Human Umbilical Vein Endothelial Cells and coronary artery porcine Smooth Muscle Cells grown to confluence over platinum black electrodes in clinically relevant populations. These measurements were obtained, using a bespoke impedance spectroscopy system that autonomously performed impedance sweeps in the 1kHz to 100kHz frequency range. Analysis of the reactance component of impedance revealed distinct frequency dependent profiles for each cell type with post confluence reactance declines in Endothelial Cell populations that have not been previously reported. Such profiles provide a means of non-invasively characterising between the cell types and give an indication that impedance spectroscopic techniques may enable the non-invasive characterisation of the arterial response to stent placement.

Advanced Functional Materials Solutions to Engineering the Neural Interface

Advanced Functional Materials Solutions to Engineering the Neural Interface

Flexible Graphene Solution‐Gated Field‐Effect Transistors: Efficient Transducers for Micro‐Electrocorticography

AbstractBrain–computer interfaces and neural prostheses based on the detection of electrocorticography (ECoG) signals are rapidly growing fields of research. Several technologies are currently competing to be the first to reach the market; however, none of them fulfill yet all the requirements of the ideal interface with neurons. Thanks to its biocompatibility, low dimensionality, mechanical flexibility, and electronic properties, graphene is one of the most promising material candidates for neural interfacing. After discussing the operation of graphene solution‐gated field‐effect transistors (SGFET) and characterizing their performance in saline solution, it is reported here that this technology is suitable for μ‐ECoG recordings through studies of spontaneous slow‐wave activity, sensory‐evoked responses on the visual and auditory cortices, and synchronous activity in a rat model of epilepsy. An in‐depth comparison of the signal‐to‐noise ratio of graphene SGFETs with that of platinum black electrodes confirms that graphene SGFET technology is approaching the performance of state‐of‐the art neural technologies.

Layered Xerogel Films Incorporating Monolayer‐Protected Cluster Networks on Platinum‐Black‐Modified Electrodes for Enhanced Sensitivity in First‐Generation Uric Acid Biosensing

AbstractAmperometric uric acid (UA) biosensing schemes incorporating networks of alkanethiolate‐protected gold nanoparticles, monolayer protected clusters (MPCs), and platinum black (Pt‐B) electrode modification through the layer‐by‐layer construction of xerogels are investigated. MPC doping and Pt‐B augmentation are implemented within hydroxymethyltriethoxysilane xerogel bilayers at platinum electrodes. The first xerogel adlayer is doped with an MPC network and houses uricase for the enzymatic reaction required for first‐generation schemes. Polyluminol–aniline and polyurethane are used as selective/stabilizing interfacial layers. The sensing performance with and without Pt‐B and/or MPC doping is assessed by amperometry with standardized UA injections. The use of each individual material results in an enhancement of UA sensitivity compared with analogous films without these materials. The use of Pt‐B and MPC doping in concert results in a biosensor design with the highest observed UA sensitivity (0.97 μA mm−1) and fast, linear responses over physiologically relevant UA concentrations. Enhancement is attributed to Pt‐B providing increased electrode surface area and integration into the xerogel for greater electronic coupling of the MPC network and more efficient reporting of H2O2 oxidation. The findings have implications for advancing clinical in vivo sensing devices that require scalability or additional biocompatibility layering, both of which would benefit from signal enhancement strategies.

Rough Gold Electrodes for Decreasing Impedance at the Electrolyte/Electrode Interface

Electrode polarization at the electrolyte/electrode interface is often undesirable for bio-sensing applications, where charge accumulated over an electrode at constant potential causes large potential drop at the interface and low measurement sensitivity. In this study, novel rough electrodes were developed for decreasing electrical impedance at the interface. The electrodes were fabricated using electrochemical deposition of gold and sintering of gold nanoparticles. The performances of the gold electrodes were compared with platinum black electrodes. A constant phase element model was used to describe the interfacial impedance. Hundred folds of decrease in interfacial impedance were observed for fractal gold electrodes and platinum black. Biotoxicity, contact angle, and surface morphology of the electrodes were investigated. Relatively low toxicity and hydrophilic nature of the fractal and granulated gold electrodes make them suitable for bioimpedance and cell electromanipulation studies compared to platinum black electrodes which are both hydrophobic and toxic.

Simultaneous Neuronal Activity Measurement Using a Microelectrode Array Recording and Voltage Sensitive Dye Imaging

Simultaneous Neuronal Activity Measurement Using a Microelectrode Array Recording and Voltage Sensitive Dye Imaging

Electrochemical Bubble-Based Bidirectional Microfluidic Transport

With the aim of application to biochemical analyses, efficient bidirectional microfluidic transport was achieved through the reversible electrochemical production and shrinkage of hydrogen bubbles. A three-electrode system with a platinum black working electrode, a Ag/AgCl reference electrode, and a platinum auxiliary electrode was incorporated into a poly(dimethylsiloxane) structure containing the necessary flow channels and compartments. The influence of the electrode and flow channel structures on the operation of the system was investigated. The production and shrinkage of bubbles was achieved by applying appropriate potentials to the working electrode, which minimized the influence of spontaneous shrinkage resulting from the oxidizing effect of dissolved oxygen. Device performance depended on the structure of the working electrode, meaning that further optimization will be necessary. The device was shown to withdraw solution through a minimally invasive needle and to process liquid plugs in a microfl...

Characterization of high capacitance electrodes for the application of direct current electrical nerve block.

Direct current (DC) can briefly produce a reversible nerve conduction block in acute experiments. However, irreversible reactions at the electrode-tissue interface have prevented its use in both acute and chronic settings. A high capacitance material (platinum black) using a charge-balanced waveform was evaluated to determine whether brief DC block (13 s) could be achieved repeatedly (>100 cycles) without causing acute irreversible reduction in nerve conduction. Electrochemical techniques were used to characterize the electrodes to determine appropriate waveform parameters. In vivo experiments on DC motor conduction block of the rat sciatic nerve were performed to characterize the acute neural response to this novel nerve block system. Complete nerve motor conduction block of the rat sciatic nerve was possible in all experiments, with the block threshold ranging from -0.15 to -3.0 mA. DC pulses were applied for 100 cycles with no nerve conduction reduction in four of the six platinum black electrodes tested. However, two of the six electrodes exhibited irreversible conduction degradation despite charge delivery that was within the initial Q (capacitance) value of the electrode. Degradation of material properties occurred in all experiments, pointing to a possible cause of the reduction in nerve conduction in some platinum black experiments .

Phonon-assisted near-field activation of electron transfer

An optical near field should promote phonon-assisted multiple excitation in nanoscale structures. With the phonon-assisted process, greater catalytic activity is expected without heating. To confirm this effect, photo-induced current generation using platinum black electrodes in ferricyanide solution (an absorption band-edge wavelength of 470 nm) under visible light irradiation continuous wave [(CW), λ=532 nm ] was observed. Higher order dependence of the generated current density on the incident light power was observed, indicating two-step activation of electron transfer, which originated from the phonon-assisted near-field effect on the nanostructured surface of the electrode.

Fabrication and Optimization of Membrane Electrode Assembly with Support-Less Platinum Catalysts for Space Applications

Hydrogen-oxygen fuel cell technology is a critical component for crewed space exploration mission beyond low earth orbit. While lowering platinum loading is of paramount importance for automotive fuel cells, it is not a significant constraint for MEAs used for space applications. As such, support-less platinum black catalysts is a viable choice. Historically, surfactant-stabilized polytetrafluoroethylene (PTFE) emulsion is used as the binder for platinum black electrode. High temperature treatment steps needed for the PTFE emulsion prevents the direct deposition of the electrocatalysts onto the Nafion® membrane. In this study, two alternative materials have been used to replace PTFE emulsion. These include surfactant-free PTFE fine particles and functionalized carbon nanotube with Nafion®. An ultrasonic spray deposition technique was applied to directly deposit support-less Pt black catalyst ink onto the Nafion® membrane. The fabrication process was optimized to produce high performance membrane electrode assemblies that approaching NASA performance target.