Amperometric Electrochemical Sensors Research Articles

Noise reduction of amperometric electrochemical sensor using current compensation on transimpedance amplifier for dissolved oxygen measurement

Noise reduction of amperometric electrochemical sensor using current compensation on transimpedance amplifier for dissolved oxygen measurement

An amperometric electrochemical sensor based on hierarchical dual- microporous structure polypyrrole nanoparticles for determination of pyrogallol in the aquatic environmental samples

Pyrogallol (PY) is commonly found as inherent toxicity of industrial effluents which easily enter to the aquatic environment; owing to its oxygen free radicals which causes several health issues. We report a highly sensitive and selective pyrogallol (PY) sensor using hierarchical dual-microporous polypyrrole nanoparticle-modified screen-printed carbon electrode (MPNPs/SPCE). The proposed electrode material for the cost-effective and rapid estimation of PY in the environmental water samples. Hierarchical dual-microporous polypyrrole nanoparticles were prepared through the simple chemical polymerization of pyrrole using Pluronic F-127 as the surfactant. The MPNPs possess well-defined dual micropore (∼0.52 and ∼ 0.67 nm) and a large BET surface area (183 m2/g). The electro-oxidation behavior of PY was examined by cyclic voltammetry and amperometric technique. Hierarchical structure with dual-microporous networks, and large specific surface area of MPNPs were assumed to be greatly enhanced the adsorption rate and a fast facilitate ion transfer for PY sensor. Owing to the effective coupling of hydrogen bonding (interaction between –OH group of PY and –NH group of polymer chain) and π -π interactions (between PPy rings and the PY aromatic rings) can offer more accessible electrochemical active sites and electrolyte/electrode contact interfaces for rapid electro-oxidation response. As a result, wide linear range (0.05–130 μM), good detection limit (0.03 μM), and high sensitivity (1.213 μA μM−1 cm−2) toward PY surpass those of other modified electrodes. Furthermore, MPNPs/SPCE system exhibited desirable selectivities, good steady stabilities, and reproducibilities as PY sensors. Real domestic, industrial, and sewage environmental water samples were analyzed, with quantification data compared with those obtained by HPLC.

Fabrication of Highly Sensitive Pt-black Electrochemical Sensors for GABA Detection.

GABA (Gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the central nervous system of mammals. It is known to be related with various neurological disorders. GABA plays a crucial role in normal neuronal activity, information processing and plasticity, and neuronal network synchronization. To date, microdialysis has been widely used to monitor the level of GABA but the temporal and spatial resolution is limited. Besides, electrochemical sensors for neurotransmitter measurement, having high temporal and spatial resolution, overcome this problem. Here, using a cost-effective method of electrodeposition of platinum black (Pt-black), a highly sensitive, GABA specific, amperometric electrochemical sensor is fabricated. Nanostructured Pt-black increases the active surface area of the electrode contributing to higher sensitivity. Along with that, a self-referencing site and an exclusion layer are integrated to increase the selectivity and the signal-to-noise ratio (SNR) of the biosensor. This provides a prototype for a highly sensitive GABA sensor that could later be used to study various neurological disorders related to GABA concentrations.Clinical Relevance- This electrochemical sensor allows real-time monitoring of major inhibitory neurotransmitter (GABA) with high sensitivity which can be used for studying various neurological disorders.

Novel sinuous band microelectrode array for electrochemical amperometric sensing

Pursuing a higher response signal is the core challenge in improving the detection performance of a microelectrode-based amperometric electrochemical sensor. Band microelectrode arrays (bMEAs) are attractive due to their high response current and economical fabrication process. However, further amplifying the response current by arranging the array more compactly or increasing its size is generally hindered by the shielding effect or the restricted construction region. A novel array of sinuous band microelectrodes (sbMEA) is proposed, produced by deforming a bMEA by tilting and bending. Its response and diffusion characteristics are simulated and analyzed. The effects of structural parameters on its performance are revealed, and their optimal value is deduced. The simulation demonstrates that a sbMEA can generate a larger current than a MEA of traditional shape. Production of such a sbMEA does not involve any additional fabrication costs compared with a bMEA. Cyclic voltammetry (CV) tests with potassium ferrocyanide solution verify the theoretical performance of the sbMEA, and a 10% higher current was obtained compared to the corresponding bMEA.

Mesoporous CuCo2O4 rods modified glassy carbon electrode as a novel non-enzymatic amperometric electrochemical sensors with high-sensitive ascorbic acid recognition

A simple, rapid and high stability analytical method development for determination ascorbic acid (AA) is using the glassy carbon electrode (GCE) embellished with mesoporous CuCo2O4 rods as a nonenzymatic amperometric sensor. The mesoporous CuCo2O4 rods were prepared by hydrothermal method adopting NH4F as a surfactant to synthesize triumphantly are employed. The sample is pure spinel CuCo2O4 rods with mesoporous structure. It is excellent electrocatalytic performances for AA is measured by I-t curve. The sensitivity of the mesoporous CuCo2O4 rods sensor is up to 9.482 mA mM−1 cm−2 within linearity range of AA concentration (1–100 μM) and 2.474 mA mM−1 cm−2 within linearity range of AA concentration (100–1000 μM), respectively. The detection limit is down to 0.21 μM with correlation coefficient R2 = 0.99. The CuCo2O4/GCE AA sensor exhibits excellent electrochemical stability, repeatability and selectivity, and actual measurement for vitamin C tablets.

Using Simulations to Guide the Design of Amperometric Electrochemical Sensors Based on Mediated Electron Transfer

AbstractMediated electron‐transfer sensors provide a practical means of detection for species for whom direct electron‐transfer sensors are impractical. Through the use of numerical simulation, the design and optimisation of mediated electron‐transfer sensors are presented in this work where we specifically consider the mediation as an irreversible process. Comparison is made between sensors employing the mediator as an adsorbed monolayer on the electrode's surface and sensors employing it as a soluble additive to the sample, with the former being concluded as preferable due to improved detection limits and practicality. Studies are performed for the optimisation of the electrode radius, mediating chemical rate constant and scan rate, with consideration also given to the capacitive current. Triangular and semi‐circular sweep voltammetry are compared in the context of mediating electron‐transfer sensor design. It is concluded that competition between the Faradaic and capacitive currents is a primary limitation for this technique.

Copper oxide immobilized clay nano architectures as an efficient electrochemical sensing platform for hydrogen peroxide

An electrochemical sensor for hydrogen peroxide (H2O2) present in face bleach cream is fabricated using a composite based on bentonite (Bt) clay and copper oxide (CuO) nanoparticles (CuO-Bt). The CuO nanoparticles’ immobilization into Bt was carried out by a two-step process in which Cu2+ is ion-exchanged into Bt layers (Cu2+-Bt) in the first step followed by the chemical reaction of NaOH with Cu2+-Bt in the second step to get the target material, CuO nanoparticles immobilized Bt (CuO-Bt). The successful immobilization of CuO nanoparticles into Bt is investigated by a variety of techniques like scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy, UV-Vis spectroscopy, and electrochemical methods. The CuO-Bt composite is coated on a glassy carbon electrode and used as a selective electrochemical sensing platform for the determination of H2O2 based on the significant electrocatalytic property of CuO-Bt towards the H2O2 oxidation. This amperometric electrochemical sensor shows two linear detection ranges (5–50 μM and 50–10000 μM) with a limit of detection of 4.9 μM. The sensitivity is calculated to be 0.06 µA µM−1 cm−2. This electrochemical sensor exhibits high selectivity, stability, and practical applicability for the H2O2 determination in real samples.

SUN-299 Flash Glucose Sensor Monitoring for Patients with Endogenous Hyperinsulinaemic Hypoglycaemia

Flash Glucose Sensor Monitoring for patients with endogenous hyperinsulinaemic hypoglycaemiaBackground:Flash glucose monitoring systems (FGS) have recently been introduced and measure interstitial glucose using an amperometric electrochemical sensor assay, and are increasingly used to provide a convenient means to monitor levels on a minute-by-minute basis over two weeks in ambulatory patients with diabetes. Although continuous glucose monitoring systems have been previously used in patients with insulinoma,(1) to our knowledge, FGS use has only been described once previously in an adult patient with an insulinoma.(2) Here, we describe use of this system in 6 patients with confirmed endogenous hyperinsulinaemic hypoglycaemia, especially for the critical nocturnal period.Methods and patients:FGS data obtained over each 2-week monitoring was reviewed in 6 patients seen between 2018 and 2019: 5 had a biochemically proven insulinoma and 1 had Hirata’s syndrome. In 4 patients, follow-up readings were obtained after adjustment of glucose-raising medication: two on octreotide, one on diazoxide and one on diazoxide and dexamethasone.Results:Median age was 63 years (range 37–83). In the 4 patients with more than one 2-week FGS assessment comparison between first and last readings demonstrated that the average duration of hypoglycaemia (<4mmol/L) 126, 171, 173 and 282 minutes improved to 46, 128, 30 and 0 minutes, respectively. The percentage of glucose readings below target (<4mmol/L) improved from 8%, 58%, 4%, and 47% to 1%, 39%, 0%, and 0%, respectively. The mean glucose was 5.9, 3.9, 7.8, and 4.4 mmol/L, which improved to 10.9, 5.0, 7.9, and 7.5 mmol/L respectively. The lowest average glucose was nocturnal (22:00-06:00) (5.8, 3.3, 6.5, and 4.1 mmol/L) which showed significant improvement after adjustment of medications (11.3, 4.2, 7.2, and 5.7 mmol/L). At least 2 of these 4 patients had well documented impaired awareness of hypoglycaemia based on diminished classical adrenergic symptoms. Among the two patients who had only one 2-week FGS assessment, one went on to have curative successful surgery and the second patient who had Hirata’s syndrome did not have significant detectable hypoglycaemia.Conclusion:FGS is a convenient tool that may be used to monitor and adjust therapy in patients with endogenous hyperinsulinism. In carefully selected patients, FGS may allow domiciliary glycaemic management avoiding the need for hospital admission for monitoring purposes.

Electrochemical Gas Sensor Integrated with Vanadium Monoxide Nanowires for Monitoring Low Concentrations of Ammonia Emission

An electrochemical sensor for the detection of extremely low concentration of ammonia (1 part per billion, ppb) was fabricated by integrating vanadium monoxide (VOx; x = 0.8–1.2) nanowires on the platinum electrodes. The nanowire-based sensor responds at room temperature non-linearly to a staircase sequence of ammonia from 1 ppb to 100 ppb. The rise and fall time of the nanowire sensor was found to be 10 s and 9 s, respectively. While the immobilization of VO nanowires increased the electrochemical surface area, the defect rich and ionic nature of the VO surface (V2+O2−) facilitated the chemical interaction and adsorption of polar ammonia molecules as evident in the room temperature response of the VO@Pt amperometric electrochemical sensor. The availability of metal centered d-electrons and the semiconductor nature of vanadium monoxide lowered the interfacial resistance of the nanowire-modified sensor enabling the lower detection limit of ammonia. The sensor seems to respond to CH4, H2S and C3H6 as well although the NH3 response is nearly six-fold compared to these common interfering compounds. The results pave the way for a low-cost alternative paper-based sensor to monitor ammonia emissions primarily from confined animal feeding operations (CAFOs).

Real-Time Modeling and Correction of Sensor Inputs and Outputs for Increased Accuracy and Reliability

Mathematical modeling was employed for automatic, real-time interrogation and correction of amperometric electrochemical gas sensors (AES) deployed in instruments for industrial hygiene applications. The interrogation involved two steps which were analyzed using various mathematical modeling techniques to determine the “goodness” of the sensor and to correct its output for small changes due to aging and environmental conditions. The first interrogation was a physical interrogation of the flow path into the sensor by supplying a driving force at the face of the sensor, either by exhaled human breath, or by acoustic sound pressure applied to diffusion barriers protecting the sensor, ensuring that the flow path was sufficiently open for detection of hazardous gases. The second interrogation was an electronic interrogation of the sensor itself, achieved by applying a small potential or current pulse to the working electrode of the sensor and deconvoluting its response to make small corrections to the sensor signal. These two steps provide periodic, real-time, and automatic surveillance and correction of AES, increasing robustness, reliability and accuracy, and user confidence, while decreasing calibration frequency, maintenance, and cost-of-ownership. Validation testing over sensors of various designs indicated a greater than 98% reliability of the sensor/instrument interrogation technique.

Sensing Behaviour Investigation of Amperometric Electrochemical NH3 Sensor: Optimization of Lanthanum Gallate Based Electrolyte Composition

To delineate the ammonia sensing mechanism by amperometric sensors a series of lanthanum gallate based electrolytes having nominal compositions of La0.8Sr0.2Ga0.8Mg0.2−xNixO3 (0 ≤ x ≤ 0.2) and La0.8Sr0.2Ga1−yFeyO3 (0.01 ≤ y ≤ 0.1) were prepared by solution combustion technique. Phase purity of electrolyte pellets was achieved by high temperature sintering process. Aforementioned electrolyte compositions were investigated for NH3 sensing performance in the temperature range of 300 °C–550 °C. Exposing the sensors alternately to the base gas (5% O2 + N2) and 3–40 ppm NH3 in base gas. Effect of oxygen pumping current on sensing mechanism was studied. The electrolytes with 10 mol% Ni and 5 mol% Fe doping showed the highest sensitivity of 35 and 43 μA decade−1 at 400 °C and 450 °C respectively. Conductivity measurements showed conductivity of 526 × 10−5 at 400 °C and 1080 × 10−5 S cm−1 at 450 °C for La0.8Sr0.2Ga0.8Mg0.1Ni0.1O3 and La0.8Sr0.2Ga0.95Fe0.05O3 respectively. A correlation between conductivity and gas sensing was established. Finally, a mechanism based on the hypothesis of defect cluster formation due to aliovalent doping that enhanced conductivity coupled with oxygen pumping current was proposed.

Fabrication of Highely Sensitive Non-Enzymatic Glucose Sensor Based on Highly Porous Cu/Cu2o/CuO Embedded in N Doped Carbon Aerogel

A novel nanocomposite, Cu/Cu2O/CuO embedded in N-doped carbon aerogel was fabricated using egg albumin and first time used as enzyme-free amperometric electrochemical glucose sensor. Excitingly, egg white played a crucial role in the in-situ formation of highly porous, small size, well dispersed Cu/Cu2O/CuO nanoparticles in N-doped carbon aerogel. The Cu/Cu2O/CuO-NC modified electrode was employed for non-enzymatic glucose detection where it exhibited a detection limit of 0.40 M and an outstanding sensitivity of 7892 A cm−2 mM−1 which is superior to existing cu based modified electrodes. The high sensitivity was attributed to the synergy arising from the ternary compositions embedded in N-doped carbon interfacing with multiple Cu redox couples and high surface area. The Cu/Cu2O/CuO-NC modified electrode also showed excellent selectivity in detecting glucose in the presence of interfering species, including chloride salts of Na+, K+, Ca2+, and anions of ascorbic acid (AA), dopamine (DA), and uric acid (UA). This simple and scalable carbonization technique will attract interest and enable in designing other high-performance metal/metal oxide embedded in N-doped carbon composites for commercial glucose sensing applications.

Printed Organic Circuit Systems for Wearable Lactate Sensors

Wearable sensor devices that enable continuous real-time monitoring and analysis of biological information from the human body are promising in the fields of sports, healthcare, and medical applications. A variety of biomarkers in body fluids (such as perspiration, saliva) can be continuously detected by a wearable electrochemical sensing system, which enables in situ analysis of physiological signals. An enzyme-based amperometric sensor is one of the most important electrochemical sensors owing to the high selectivity and the connectivity to information technologies. So far, the quantitative measurement of metabolites in human fluids, including lactate, glucose, and uric acid, have been carried out using enzyme-based amperometric sensors and conventional potentiostat systems. A potentiostat is the electronic hardware which controls the three-electrode cell for electrochemical experiments and possesses two functions: (1) maintaining the potential of the working electrode (WE) at a constant level with respect to the reference electrode (RE) by adjusting the current at a counter electrode (CE), and (2) converting the current at the working electrode to the voltage by a transimpedance amplifier with a high gain. Hence, both the enzyme-based amperometric sensors and the potentiostat need to be integrated in the wearable devices. Organic thin-film transistors (OTFTs) have potential for realizing ultra-thin, lightweight, and flexible circuit components of the potentiostat for wearable sensor devices owing to their advantages such as the small Young’s modulus, biocompatibility, and the processability of direct printing onto plastic films. Printability is an attraction of OTFTs because organic materials can be dissolved in organic solvents, which enables roll-to-roll manufacture of large-area devices on flexible substrates. These features are significant requirements for making the low-cost devices attachable onto human tissues or clothes like a patch. So far, OTFTs have been utilized as amplifiers for potentiometric electrochemical sensors, which is called extended-gate type OTFTs. Although the potentiometric measurement is applicable to enzymatic sensors, it exhibits an irreversible and slow response in several minutes, which is not suitable to real-time sensing. On the other hand, the amperometric measurement based on enzymatic sensors exhibits a reversible and fast response in several tens of seconds. OTFTs have never been utilized for amperometric sensors since the three-electrode system requires complex integrated circuits rather than the simple extended-gate type OTFTs. In this work, we demonstrate a novel flexible and printed organic circuit system for wearable amperometric electrochemical sensors, implemented with two OTFT-based negative-feedback inverters. The inverters employed pseudo-CMOS design for obtaining rail-to-rail operation and low output impedance, and consisted of the OTFTs based on a blend of a small molecular p-type semiconductor and polystyrene for the active layer. The first inverter was utilized to maintain the potential at the WE at a constant level with respect to the RE. The second inverter was utilized to convert the current at the WE into voltage with a tunable gain of 106–107 V/A. A lactate sensor with a lactate oxidase membrane was used as the WE. This simple system worked like a potentiostat for electrochemical measurements, and enabled the quantitative and real-time measurement of lactate concentration with high sensitivity of 1 V/mM and a short response time of a hundred seconds. These results will allow organic semiconductor devices to have potential for realizing extremely thin and lightweight wearable devices for in situ monitoring of metabolites in body fluids.

Pulsed Potential Amperometric Electrochemical Gas Sensors

Pulsed electrochemical techniques are well known and are well reviewed. The various discussions and derivations of the theory of pulsed voltammetry or polarography extant make clear the motivations behind the development of these techniques: increasing the analytical sensitivity of these methods by separating, in time, the charging current and the Faradaic current. There are at least three critical criteria for the success of pulsed voltammetric methods: The potential pulse should be small: > 0.059/n V @ 25C.The time between pulses should be long: for electrode area of 1 cm2, several seconds.The electrode area should be minimized: < 1 cm2, down to 1 µm2. All of these efforts had one goal in mind; minimizing the charging current with respect to the Faradaic current. Pulsed voltammetric techniques lowered the typical useful concentration range of electroanalytical methods from parts-per-thousand (10-3) to parts per million (ppm, 10-6) and lower. The above discussion applies to classic solution-oriented electroanalytical techniques. Amperometric electrochemical gas sensors differ in several important ways which should limit or eliminate the usefulness of pulse techniques in this application. Amperometric electrochemical gas sensors are ubiquitous in the modern industrial workplace, commonly deployed for worker protection against toxic and noxious gases. The heart of any good electrochemical gas sensor is the gas diffusion electrode, which is typically the working electrode in sensors. The gas diffusion electrode allows the easy confluence of three things, the electrocatalyst of which the electrode is comprised, usually a metal, the internal electrolyte of the sensor, usually a liquid solution, and the gas of interest. This confluence is often referred to as the “triple point.” To maximize the sensitivity of a sensor, maximize the number of triple points. This is commonly accomplished by using finely divided, high surface area catalytic metals, such as platinum (Pt) or iridium (Ir) “blacks.” As gas diffusion electrodes commonly use such high surface area metal particles, their actual, usable electrochemically accessible surface area, and hence, electrical capacitance often far exceed their geometric area, and vary greatly from sensor (electrode) type to sensor type, and may approach 0.5 m2. We have recently applied pulsed potential voltammetric techniques to the high surface area electrodes commonly employed in electrochemical gas sensors with great utility. The accompanying graph depicts the results of a typical experiment. This sensor utilized a rough gold working electrode with an electrochemically accessible surface area of approximately 100 cm2. The potential was switched between -150 and +250 mV (vs an internal Pt|air pseudo-reference electrode) every 0.5 sec. The traces in the figure are offset for clarity. The upper trace in the figure is the raw response recorded with a Bio-Logic VMP3 potentiostat. The data was collected every 0.1 sec. Ten (10) ppm nitrogen dioxide (NO2), in air, was applied to the sensor at a flow rate of 0.25 l/min, beginning at the 5 minute time and switched back to clean air at the same flow rate at the 10 minute mark. The bottom traces depict the results of current sampling the sensor response just before the potential of the working electrode was switched to either -150 mV or 250 mV (a 400 mV pulse). The pulse rate was 0.5 seconds; therefore, the current was sampled approximately 0.49 sec after the application of the potential pulse. As can be seen in the lower traces, very serviceable sensor responses were obtained in this manner for the application of 10 ppm nitrogen dioxide (NO2) in air (open circles, reduction) or 10 ppm nitric oxide (NO) in air (open diamonds, oxidation). The response time, noise, other figures of merit are very similar to data obtained from this same sensor operated at a single potential of -150 mV (for the reduction of nitrogen dioxide) or at +250 mV (for the oxidation of nitric oxide). Using this technique, we have produced a single sensor that allows the simultaneous detection of both nitric oxide and nitrogen dioxide at concentrations important for worker protection. We have extended this technique to the detection of other gases, including oxygen at and near ambient conditions (20.8 vol-% at sea level and 25 C). Figure 1

(Invited) Electrochemical Biosensors Based on CMOS LSI Chips

Electrochemical biosensors are the sensors for bio-related substances/phenomena based on electrochemical principles. While optical and colorimetric biosensors are widely used for clinical and research purposes, electrochemical biosensors offer various advantages such as compact/affordable instrumentation and high throughput. As a platform of such electrochemical biosensors, a complementary metal-oxide-semiconductor (CMOS) large-scale integrated (LSI) circuit chip can be an ideal platform for its microscale structures and electronic circuit integration. In this paper, general overview and some examples of such CMOS-based electrochemical sensing experiments/simulations are presented. The electrochemical methods can be categorized into three types, that is, (i) amperometoric and voltammetric method, (ii) potentiometric method, and (iii) impedance method. In the amperometric method, electrochemical current is measured as a function of time under constant voltage application, while voltammetric method often means that the voltage is swept and current vs. voltage is plotted. On the other hand, in potentiometric method, no voltage is applied and therefore no current will be induced. Instead, open-circuit potential of a floating electrode in contact with sample solution is measured. Finally, in impedance method, the relation between sinusoidal voltage applied to the sample solution and resulting sinusoidal current is measured as a complex valued impedance. We have been working on various CMOS-based electrochemical biosensing experiments and simulations. Experimental demonstrations of amperometric and voltammetric methods can been seen in [1, 2], where carbon-ink electrodes are formed on CMOS chip and used to measure current under constant/swept voltages. Computer simulation of amperometric measurement using CMOS on-chip electrode has also been presented in [3]. As for the potentiometric method, we have demonstrated a potentiometric glucose sensor with carbon electrode and enzyme-functionalized chromatography paper on CMOS chip [4]. Computer simulation of ion-sensitive field-effect transistors (ISFET) for DNA sensing [5, 6] and lipid bilayer (cell membrane) detection [7] have also been demonstrated. In terms of impedance measurement using CMOS, we have developed a computationally efficient three-dimensional model of electrolytic solution and living cells for finite-element method (FEM) simulation. Using this, we have demonstrated computer simulation of impedance measurement of single mammalian cell or bacterial cell using microscale electrode on CMOS chip [8, 9]. Compact formulae for equivalent circuit model of such cell/electrolyte/electrode system have demonstrated a good accuracy [9]. Our current goal is the experimental implementation of such single cell monitoring by impedance measurement using CMOS on-chip microelectrodes. In summary, we have been developing both experimental and simulation techniques of the major electrochemical biosensing methods using CMOS on-chip microelectrodes. Such effort would lead to a comprehensive understanding of multi-modal electrochemical biosensing where CMOS LSI chips are used as a platform. This work was partially supported by JSPS KAKENHI Grant Numbers 25220906 and 26289111, as well as VLSI Design and Education Center (VDEC), the University of Tokyo in collaboration with Synopsys, Cadence Design Systems, and Mentor Graphics. [1] M. Miki, S. Iwahara, and S. Uno, “A hybrid system of carbon ink electrodes and chromatography paper on a CMOS chip and its application to Enzymatic glucose sensor”, Jpn. J. Appl. Phys., vol. 53, p. 04EL06 (2014). [2] J. Eguchi, K. Yamaoka, and S. Uno, “Simultaneous Electrochemical Measurement using Paper Fluidic Channel on CMOS Chip”, TELKOMNIKA, vol. 15, no. 2, pp. 847-852 (2017). [3] J. Hasegawa, S. Uno, and K. Nakazato, “Amperometric Electrochemical Sensor Array for On-Chip Simultaneous Imaging: Circuit and Microelectrode Design Considerations”, Jpn. J. Appl. Phys., vol. 50, p. 04DL03 (2011). [4] K. Yamaoka, J. Eguchi, and S. Uno, “Potentiometric Glucose Detection by Paper-based Electrochemical Sensor on CMOS Chip”, TELKOMNIKA, vol. 15, no. 2, pp. 836-841 (2017). [5] Y. Nishio, S. Uno, and K. Nakazato, “Three-Dimensional Simulation of DNA Sensing by Ion-Sensitive Field-Effect Transistor: Optimization of DNA Position and Orientation”, Jpn. J. Appl. Phys., vol. 52, p. 04CL01 (2013). [6] S. Uno, M. Iio, H. Ozawa, and K. Nakazato, “Full Three-dimensional Simulation of ISFET Flatband Voltage Shift due to DNA Immobilization and Hybridization”, Jpn. J. Appl. Phys., vol. 49, no. 1, p. 01AG07 (2010). [7] S. Uno, “Computer simulation of lipid bilayer detection using ion-sensitive field-effect transistors” SPIE BIOS, San Francisco, USA (January 26, 2012) 8231-28. [8] S. Uno, “Simulation of Microelectrode Electrochemical Impedance Sensor for Single-cell Monitoring”, The 11th International Symposium on Electrochemical Micro & Nanosystem Technologies (EMNT2016), Brussel, Belgium (August 17-19, 2016), P-18. [9] S. Uno, and K. Nakazato “Numerical and Equivalent Circuit Analysis of Electrochemical Impedance Spectroscopy of Single Bacterial Cell Detection using CMOS LSI Chip”, 11th International Symposium on Electrochemical Impedance Analysis 2017, Camogli, Italy (November 7-11, 2017).

Lanthanum gallate based amperometric electrochemical sensor for detecting ammonia in ppm level: Optimization of electrode compositions

Fabrication of a highly sensitive amperometric electrochemical gas sensor would require optimisation of the electrode materials and rigorous testing of device performance under different processing conditions. An ammonia sensor based on lanthanum gallate electrolyte having the composition La0.8Sr0.2Ga0.8Mg0.1Ni0.1O3 (LSGMN) has been investigated for its detecting at ppm level. A single phase solid solution of 30 mol% Zr4+ in CeO2 (CZ73) as an active (sensing) electrode yielded optimum results. Similarly, La0.5Sr0.5Mn0.8Ni0.2O3 (LSMN5582) was found to be the best composition for the inactive (reference) electrode. All the devices were found to have maximum sensitivity at 400 °C and a typical response and recovery times of 40 s and 110 s respectively. Moreover, they exhibited better efficiency in amperometric mode as compared to potentiometric mode and were stable up to several cycles of operation. It was established through mechanistic studies that even though both the electrodes were simultaneously exposed to both the gases, higher sensitivity was obtained when CZ73 was biased at +1 V with respect to LSMN5582 as against −1 V, implying that NH3 oxidation took place preferentially at CZ73 whereas oxygen reduction took place at the inactive electrode. Step by step sensitivity at 400 °C improved from 28.2 to 35 μA/decade. Further, the electrolyte thickness was decreased to 0.4 mm in view of reducing the internal resistance and a prototype device was fabricated that yielded enhanced sensitivity of 49 μA/decade under optimized conditions.

Amperometric Gas Sensors as a Low Cost Emerging Technology Platform for Air Quality Monitoring Applications: A Review.

This review examines the use of amperometric electrochemical gas sensors for monitoring inorganic gases that affect urban air quality. First, we consider amperometric gas sensor technology including its development toward specifically designed air quality sensors. We then review recent academic and research organizations' studies where this technology has been trialed for air quality monitoring applications: early studies showed the potential of electrochemical gas sensors when colocated with reference Air Quality Monitoring (AQM) stations. Spatially dense networks with fast temporal resolution provide information not available from sparse AQMs with longer recording intervals. We review how this technology is being offered as commercial urban air quality networks and consider the remaining challenges. Sensors must be sensitive, selective, and stable; air quality monitors/nodes must be electronically and mechanically well designed. Data correction is required and models with differing levels of sophistication are being designed. Data analysis and validation is possibly the biggest remaining hurdle needed to deliver reliable concentration readings. Finally, this review also considers the roles of companies, urban infrastructure requirements, and public research in the development of this technology.

New Titanium Dioxide-Based Heterojunction Nanohybrid for Highly Selective Photoelectrochemical-Electrochemical Dual-Mode Sensors.

A new titanium dioxide (TiO2)-based heterojunction nanohybrid (HJNH) composed of TiO2, graphene (G), poly[3-aminophenylboronic acid] (PAPBA), and gold nanoparticles (Au NPs) was synthesized and designated as TiO2(G) NW@PAPBA-Au HJNH. The TiO2(G) NW@PAPBA-Au HJNH possesses dual-mode signal photoelectrochemical (PEC) and electrochemical transduction capabilities to sense glucose and glycated hemoglobin (HbA1c) independently. The synthesis of the HJNH material involved two sequential stages: (i) simple electrospinning synthesis of G-embedded TiO2 nanowires [TiO2(G) NWs] and (ii) one-step synthesis of Au NP-dispersed PAPBA nanocomposite (NC) in the presence of TiO2(G) NWs. The as-synthesized TiO2(G) NW@PAPBA-Au HJNH was characterized by field emission scanning electron microscopy, field emission transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermogravimetric analysis, and UV-visible diffuse reflectance spectroscopy. A PEC platform was developed with TiO2(G) NW@PAPBA-Au HJNH for the selective detection of glucose without any enzyme auxiliary. The PEC glucose sensor presents an acceptable linear range (from 0.5 to 28 mM), good sensitivity (549.58 μA mM-1 cm-2), and low detection limit (0.11 mM), which are suited for diabetes glucose monitoring. Besides, the boronic acid groups in PAPBA were utilized as a host to capture HbA1c. We fabricated the electrochemical HbA1c sensor based on monitoring the electrocatalytic reduction current of hydrogen peroxide produced by HbA1c tethered to the sensor probe. The amperometric electrochemical sensor for HbA1c exhibited linear responses to HbA1c levels from 2.0 to 10% (with a detection limit of 0.17%). Notably, the performances of the fabricated glucose and HbA1c sensors are superior in the dual-signal transduction modes as compared to the literature, suggesting the significance of the newly designed bifunctional TiO2(G) NW@PAPBA-Au HJNH.

Characterization of a Flexible Glucose Amperometric Sensor Obtained through Electroless Deposited NiP Electrodes

A flexible nickel-phosphorus (NiP) amperometric electrochemical glucose sensor is proposed. A thin layer of NiP was deposited by electroless technique directly onto the Polyethylene Terephthalate (PET) substrate. NiP electroless plating has proved to be a low cost, simple and versatile fabrication technique. The electrochemical behavior of the sensor was in agreement with the literature value, with anodic peak at 0.54 V vs Ag/AgCl. Voltammetric response of glucose was characterized, showing a good sensitivity of the device. The influence of mechanical stress (bending) on the electrochemical response and on the glucose sensing performance of the PET/NiP sensor was examined. Bending the PET/NiP electrode to small radii of curvature (up to 5mm) has no effect upon the electrochemical behavior, but an increase in sensitivity with respect to flat sensors was found.

Elimination of Sensor Maintenance By Sensor Interrogation and Correction

Amperometric electrochemical gas sensors are virtually ubiquitous and well accepted in industrial hygiene and personal safety applications. This sensor type, used initially for detection of carbon monoxide (CO) and oxygen (O2), first appeared in the 1970s. Since that time, sensors were developed to detect many other gases of interest, including hydrogen sulfide (H2S), sulfur dioxide (SO2) and chlorine (Cl2), just to name a few. Electrochemical sensors are highly accurate, have good reproducibility and linearity and are long-lived. That said, best industry practice dictates that gas detection instruments be tested regularly (every day that the instrument is used) to ensure proper functionality. Testing can take several forms, including full calibration using the test gas of interest or a simulant gas, or a calibration check or bump test. Each test requires considerable monetary investment, including a test gas source (usually a compressed gas cylinder) and delivery system that typically includes a pressure regulator and tubing. It is quite common at large industrial installations that all personnel are equipped with personal gas detectors. Clearly, providing test gas and delivery systems is a significant investment in equipment, consumables and non-productive time. This paper discusses a new gas-free bump test and correction system that eliminates the need for test gas and delivery systems, while providing on-demand exercising of all sensor and instrument functions, real time sensor signal correction for sensor aging and response to environmental conditions.[1],[2] This new sensor technology is based upon a modification dual channel amperometric gas sensor. Dual channel amperometric gas sensors have two separate working electrodes include one that is designed for carbon monoxide detection and the other intended for hydrogen sulfide detection. These two independent electrodes share a common reference electrode1,2 (RE) and counter1,2 electrode (CE). In the present application, bias potentials applied to the two working electrodes are controlled by an on-board Application Specific Integrated Circuit (ASIC). This ASIC chip also amplifies and measures currents that flow between the two working electrodes and common counter electrode. The present technology, first introduces as the H2S Pulse Sensor, also has two separate working electrodes, one to sense hydrogen sulfide, (as with a two-tox sensor) and a second electrode that responds to oxygen. Pulse Technology functions in the following manner: first, a small potential pulse is applied to the H2S working electrode; this potential pulse causes electrical current to flow between the H2S working electrode and the common counter electrode. This current is measured and analyzed by the ASIC. The current that flows within the sensor can be used to monitor or measure several items: Is the sensor present?Is the sensor conducting current?Has sensor sensitivity changed from the last pulse test?Has sensor sensitivity sensor changed enough to require re-calibration (an actual re-calibration using test gas), orCan sensor output be corrected slightly in order to maintain maximum sensor accuracy? The electrical pulse test can also determine if the sensor’s working electrode was poisoned or inhibited by an interferant gas. Immediately following the pulse test, the second oxygen-responsive working electrode is activated by the ASIC and allowed to briefly equilibrate. Once appropriate current is established for oxygen reduction in ambient air, users are prompted to exhale into the sensor inlet. Exhaled breath contains approximately 15 vol-% oxygen as compared to ambient air that contains 20.8 vol-% oxygen. Decrease in oxygen due to exhaled breath pulse supplied by users causes decrease in current that flows between the oxygen-responsive working electrode and the common counter electrode. This current change is also measured and analyzed by the ASIC. The change in current due to exhaled breath is used to determine if gaseous flow path into the sensor is free of obstruction as compared to the last successful pulse test. The exhaled breath pulse test can discriminate between open, partially-blocked and fully-blocked flow paths. Pulse Technology combines these two independent sensor function tests to provide a convenient and highly accurate and effective substitute for bump testing using calibration gas. Extensive testing of Pulse Technology indicates greater than 98% accuracy. Pulse Technology effectively eliminates daily bump testing using calibration gas and extends the interval between required full calibrations. [1]Scheffler, T. B., Devices, systems and methods for testing gas sensors and correcting gas sensor output, U.S. Patent 7,413,645 B2, August 19, 2008. [2]Scheffler, T. B., Devices, systems and methods for testing gas sensors and correcting gas sensor output, U. S. Patent 7,959,777 B2, June 14, 2011. Figure 1