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Proton-conducting solid-state electrolytes, including perovskite-type materials, hold promise for hydrogen sensor development. These sensors leverage the proton conductivity of such materials to detect hydrogen gas presence. However, achieving both high density for gas tightness and good protonic conductivity in these refractory materials can be challenging. In this study, we propose the preparation of dense pellets of BaCe 0.6 Zr 0.3 Y 0.1 O 3-δ using ZnO as a sintering aid (BCZY-Zn). These pellets were extensively characterized using X-ray diffraction and electrochemical impedance spectroscopy and compared with pellets sintered without sintering aid (BCZY). Subsequently, BCZY-Zn electrolyte was utilized to fabricate amperometric sensors for hydrogen monitoring. Finally, amperometric measurements were conducted at 500 °C while maintaining a voltage of 150 mV between electrodes. The sensors' performance was evaluated for hydrogen partial pressures ranging from 12 to 100 Pa within an argon atmosphere. Additionally, response and recovery times were calculated. [Display omitted] • XRD showed smaller lattice parameters for BCZY-Zn (4.3410 Å) than for BCZY (4.3450 Å). • Bulk, grain boundary and three electrode processes were identified in EIS. • Bulk conductivity's activation energy was mostly unaffected by ZnO. • ZnO enhanced pellet densification, reducing the activation energy. • BCZY-Zn had good sensitivity and response and recovery times from 12 to 100 Pa. [ABSTRACT FROM AUTHOR]

An amperometric sensor for ascorbic acid determination has been developed by modifying the surface of a glassy carbon electrode (GCE) with polyaspartic acid (PolyAsp), carboxylated multi‐walled carbon nanotube (c‐MWCNT), and ionic liquid (IL, 1‐butyl‐3‐methylimidazolium hexafluorophosphate). The amount of each modification material on the surface was optimized in order to achieve good analytical performance. The operating conditions of c‐MWCNT−IL/PolyAsp/GCE were optimized. The performance characteristics of c‐MWCNT−IL/PolyAsp/GCE were investigated at optimum pH (8.0) and optimum potential (+0.20 V), and the sensor responded linearly to ascorbic acid between 5.3–2766.3 μM with a sensitivity of 19.64 μA mM−1 and detection limit of 3.0 μM. Determination of ascorbic acid in vitamin C tablet, vitamin C injection solution, and orange juice was successfully performed with the presented sensor and the recovery values were found between 98.9% and 101.6%. [ABSTRACT FROM AUTHOR]

This work presents a novel compact CMOS potentiostat-designed circuit for an electrochemical cell. The proposed topology functions as a circuit interface, controlling the polarization of voltage signals at the sensor electrodes and facilitating current measurement during the oxidation–reduction process of an analyzed solution. The potentiostat, designed for CMOS technology, comprises a two-stage amplifier, two current mirror blocks coupled to this amplifier, and a CMOS push–pull output stage. The electrochemical method of cyclic voltammetry is employed, operating within a voltage range of ±0.8 V and scan rates of 10 mV/s, 25 mV/s, 100 mV/s, and 250 mV/s. The circuit is capable of reading currents ranging from 10 µA to 500 µA. Experimental results were obtained using a potassium ferrocyanide K3[Fe(CN)6] redox solution with concentrations of 10, 15, and 20 mmol/L, and their corresponding voltammograms were evaluated. The experimental results from a discrete circuit demonstrate that the proposed potentiostat topology produces outcomes consistent with those of classical topologies presented in the literature and industrial equipment. [ABSTRACT FROM AUTHOR]

Luminescent carbon nanoparticles, such as carbon quantum dots (CQDs) and graphene quantum dots (GQDs), are increasingly utilized for sarcosine detection due to their exceptional water permeability, sustained luminescence, and biocompatibility. Sarcosine as a biomarker holds significance for therapeutic purposes and disease identification. Carbon‐based sensors offer eco‐friendliness, recyclability, and affordability, making them sustainable for sensing applications across various domains. Despite the widespread use of standard sensors for sarcosine measurement, they face limitations. This paper presents a focused review of recent developments in biosensors utilizing luminescent carbon quantum dots and graphene quantum dots for sarcosine detection. Key processes are characterized by their selectivity and sensitivity to different forms of sarcosine and interfering substances like metallic ions and amino acids. The significant reaction mechanisms and detection methods for sarcosine are outlined and compared. Additionally, the challenges in developing functionalized CQDs and GQDs for further investigation are explored. In summary, luminescent carbon nanoparticles offer a promising avenue for sarcosine detection, addressing limitations of standard sensors through their cost‐effectiveness, sensitivity, and rapid response, thus holding potential for diverse sensing applications. [ABSTRACT FROM AUTHOR]

Liquid metal‐based printing techniques are emerging as an exemplary platform for harvesting non‐layered 2D materials with a thickness down to a few nanometres, leading to an ultra‐large surface‐area‐to‐volume ratio that is ideal for sensing applications. In this work, the synthesis of 2D tin dioxide (SnO2) by exfoliating the surface oxide of molten tin is reported which highlights the enhanced sensing capability of the obtained materials to ammonia (NH3) gas is reported. It is demonstrated that amperometric gas sensors based on liquid metal‐derived 2D SnO2 nanosheets can achieve excellent NH3 sensing performance at low temperature (150 °C) with and without UV light assistance. Detection over a wide range of NH3 concentrations (5–500 ppm) is observed, revealing a limit of detection at the parts per billion (ppb) level. The 2D SnO2 nanosheets also feature excellent cross‐interference performance toward different organic and inorganic gas species, showcasing a high selectivity. Further, ab initio DFT calculations reveal the NH3 adsorption mechanism is dominated by chemisorption with a charge transfer into 2D SnO2 nanosheets. In addition, a proof of concept for prototype flexible ammonia sensors is demonstrated by depositing 2D SnO2 on a polyimide substrate, signifying the high potential of employing liquid metal printed SnO2 for realizing wearable gas sensors. [ABSTRACT FROM AUTHOR]

The progressive increase in nitrate's (NO3−) presence in surface and groundwater enhances environmental and human health risks. The aim of this work is the fabrication and characterization of sensitive, real-time, low-cost, and portable amperometric sensors for low NO3− concentration detection in water. Copper (Cu) micro-flowers were electrodeposited on top of carbon screen-printed electrodes (SPCEs) via cyclic voltammetry (with voltage ranging from −1.0 V to 0.0 V at a scan rate of 0.1 V s−1). The obtained sensors exhibited a high catalytic activity toward the electro-reduction in NO3−, with a sensitivity of 44.71 μA/mM. They had a limit of detection of 0.87 µM and a good dynamic linear concentration range from 0.05 to 3 mM. The results were compared to spectrophotometric analysis. In addition, the devices exhibited good stability and a maximum standard deviation (RSD) of 5% after ten measurements; reproducibility, with a maximum RSD of 4%; and repeatability after 10 measurements with the RSD at only 5.63%. [ABSTRACT FROM AUTHOR]

Numerical models of electrochemical sensors using screen-printed electrodes (SPEs) are limited. Simulating the dynamic response of SPEs is challenging due to their complex geometry and kinetic behavior. In this paper, we present a general process by which SPEs can be modeled using commercial finite element software, COMSOL Multiphysics. Parameters such as electroactive surface area and the heterogenous rate constant were derived empirically using a commonly used redox couple of hexaammineruthenium (III), [ R u (N H 3) 6 ] 3 + , and hexaammineruthenium (II), [ R u (N H 3) 6 ] 2 + . Experimentally derived parameters were used in the model and a transient numerical simulation was run to replicate the cyclic voltagramms procured from experiment. The results show that the electroactive area was measured to be 2.3 m m 2 (± 0.674), which was less than the 3.14 m m 2 geometric area. In addition, the heterogeneous kinetic constant at various voltage scanning rates, ranging from 25 to 500 mV/s, were measured. Uncompensated resistance was measured as 301.9 Ω (± 1.6) and was also incorporated as a parameters in the model. Numerical results as represented by voltagramms shapes were consistent with experimental results. The model was able to predict the maximum anodic current density with an accuracy of 30.5%, 22.9%, 13.4%, 16.2%, 12.8%, 14.8%, and 14.6% for scan rates ranging from 25 to 500 mV/s (25, 50, 75, 100, 200, 300, 400, and 500 mV/s, respectively). The model was more accurate in predicting maximum cathodic currents with accuracy values of 1.7%, 1.2%, 5.5%, 4.1%, 1.7%, 2.4%, and 2.2% for scan rates ranging from 25 to 500 mV/s. The results demonstrate the first attempt to model the SPEs which incorporate experimentally derived parameters. These types of models are expected to help biosensor researchers simulate sensor response before fabrication and testing. [ABSTRACT FROM AUTHOR]

Four polyoxomolybdated compounds based on Tetp (Tetp = 4-[4-(2-Thiophen-2-yl-ethyl)-4H-[1, 2, 4]triazole-3-yl]-pyridine), namely [Zn(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Zn-Mo8), [Co(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Co-Mo8), [Cu4(Tetp)6(H2O)2]{H3[K(H2O)3](θ-Mo8O26)(Mo12O40)}·8H2O (Cu-Mo20) and [Cu3(Tetp)3][PMo12O40]·H2O (Cu-PMo12) are synthesized by hydrothermal methods and are used as electrode materials for supercapacitors(SCs) and electrochemical sensors. Inserting polyoxometalates (POMs) with redox active sites into transition metal compounds (TMCs) can improve the internal ion/electron transfer rate, thus effectively enhancing the electrochemical performance. Compared with the parent POMs, four compounds exhibit excellent electrochemical properties. In particular, Cu-PMo12 shows an excellent specific capacitance (812.3 F g−1 at 1 A g−1) and stability (94.42%), as well as a wide detection range (0.05 to 1250 µM) and a low detection limit (0.057 µM) for NO2- sensing. [ABSTRACT FROM AUTHOR]

Electrochemical biosensors are critical in advancing biomedical and pharmaceutical therapies because of their adaptability and cost-effectiveness. Voltammetric and amperometric sensors are of particular interest. These sensors typically consist of a specialized tip or biorecognition element and a transducer that converts biological data into readable signals. Efficient biosensor materials are essential for addressing health emergencies, with coordination polymers (CPs) and metal–organic frameworks (MOFs) showing promise. Functionalization strategies are necessary to enhance the usability of pristine MOFs, owing to issues such as low conductivity. The integration of conductive polymers with MOFs has resulted in the development of highly efficient biosensors. Both enzymatic and nonenzymatic biosensors are used for analyte detection; nonenzymatic approaches are gaining popularity owing to their durability and accuracy. MOFs and CPs have been applied in sensitive electrochemical biosensors to detect fatal brain tumors such as glioblastomas (GBM). These biosensors demonstrate enhanced selectivity and sensitivity, highlighting the potential of MOFs and CPs in advancing electrochemical biosensor technology for both in vivo and in vitro applications. [ABSTRACT FROM AUTHOR]

Glycerol is a widely used signaling bioanalyte in biotechnology. Glycerol can serve as a substrate or product of many metabolic processes in cells. Therefore, quantification of glycerol in fermentation samples with inexpensive, reliable, and rapid sensing systems is of great importance. In this work, an amperometric assay based on one-step designed electroplated functional Pd layers with controlled design was proposed for a rapid and selective measurement of glycerol in yeast fermentation medium. A novel assay utilizing electroplated Pd-sensing layers allows the quantification of glycerol in yeast fermentation medium in the presence of interfering species with RSD below 3% and recoveries ranged from 99 to 103%. The assay requires minimal sample preparation, viz. adjusting of sample pH to 12. The time taken to complete the electrochemical analysis was 3 min. Remarkably, during investigations, it was revealed that sensitivity and selectivity of glycerol determination on Pd sensors were significantly affected by its adsorption and did not depend on the surface structure of sensing layers. This study is expected to contribute to both fundamental and practical research fields related to a preliminary choice of functional sensing layers for specific biotechnology and life science applications in the future. [ABSTRACT FROM AUTHOR]

The accurate and sensitive determination of tyrosine is of paramount value. In this work, we reported the synthesis and characterization of a new nanohybrid composed of silver nanoparticles and hollow carbon nanospheres (Ag/HMCS) for the amperometric sensing of tyrosine. The Ag/HMCS nanohybrid was used to modify electrodes and to fabricate an amperometric sensor for tyrosine at a working potential of 450 mV in aqueous 0.1 M phosphate buffer at pH 7.0. Under optimal conditions, the sensor determined tyrosine from 0.08 to 100 μM with a detection limit of 0.02 μM. [ABSTRACT FROM AUTHOR]

Nitrate (NO3−) contamination from agricultural and industrial waste affects environmental water quality and can cause severe diseases if consumed in drinking water. Therefore, the detection of NO3− is a necessary precaution. This work describes the development of an electrochemical sensor for NO3− detection that combines the advantages of ordered mesoporous carbon (OMC) and copper foam (Cu foam) on a glassy carbon electrode (Cu foam/OMC/GCE). The large surface area, uniform pore structure, and large pore volume of OMC supported the electrodeposition of Cu foam to create a highly porous electrocatalytic structure for NO3− reduction. Under optimal conditions, the developed electrochemical sensor exhibited linearity from 1.0 μM to 5.0 mM and a detection limit of 1.0 μM (S/N=3). Moreover, the proposed electrochemical sensor exhibited acceptable selectivity, and good stability and reproducibility. The developed sensor detected NO3− in drinking water samples with recoveries of 88.2±0.9 to 112.5±6.3 %. [ABSTRACT FROM AUTHOR]

The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe2O4@MWCNT, to be applied as a non-enzymatic amperometric sensor for GLU. Both NiFe2O4 and NiFe2O4@MWCNT composites were properly characterized by XRD, SEM, FTIR, and Raman spectroscopy, which confirmed that the composite was successfully prepared. A glassy-carbon electrode (GCE) modified with NiFe2O4@MWCNT was investigated by cyclic voltammetry and applied for the amperometric GLU detection using batch-injection analysis (BIA). A linear working range between 50 and 600 µmol L−1 GLU with a significant increase in sensitivity (3-fold) in comparison with MWCNT/GCE was verified, with a detection limit of 36 µmol L−1. Inter-electrode measurements (n = 4, RSD = 10%) indicated that the sensor fabrication is reproducible. Furthermore, the proposed non-enzymatic sensor was selective even in the presence of other biomarkers found in urine. When applied to synthetic urine samples, recovery levels between 84 and 95% confirmed analytical accuracy and the absence of sample matrix effect. Importantly, the developed approach is simple (free of biological modifiers), fast (77 injections per hour), and practical (high-performance tool), which are suitable features for routine analyses. [ABSTRACT FROM AUTHOR]

Disposable sensors are inexpensive, user-friendly sensing tools designed for rapid single-point measurements of a target. Disposable sensors have become more and more essential as diagnostic tools due to the growing demand for quick, easy-to-access, and reliable information related to the target. Dopamine (DA), a prevalent catecholamine neurotransmitter in the human brain, is associated with central nervous system activities and directly promotes neuronal communication. For the sensitive and selective estimation of DA, an enzyme-free amperometric sensor based on polyaniline-doped multi-walled carbon nanotubes (PANI-MWCNTs) drop-coated disposable screen-printed carbon electrodes (SPCEs) was fabricated. This PANI-MWCNTs-2/SPCE sensor boasts exceptional accuracy and sensitivity when working directly with ex vivo mouse brain homogenates. The sensor exhibited a detection limit of 0.05 μM (S/N = 3), and a wide linear range from 1.0 to 200 μM. The sensor's high selectivity to DA amidst other endogenous interferents was recognized. Since the constructed sensor is enzyme-free yet biocompatible, it exhibited high stability in DA detection using ex vivo mouse brain homogenates extracted from both Parkinson's disease and control mice models. This research thus presents new insights into understanding DA release dynamics at the tissue level in both of these models. [ABSTRACT FROM AUTHOR]

Glassy carbon electrode was modified with palladium-decorated conducting poly(thionine) film to develop a simple, cost-effective, and fast amperometric sensor for the detection of H2O2. Conducting PTH film served as a porous and stable support matrix for even distribution of the Pd nanomaterials. In order to get the maximum performance from the modified electrode system, experimental conditions were optimized using chronoamperometry. The Pd/PTH@GCE electrode showed maximum performance in buffer solution at pH = 7.5 meaning it is suitable for the detection of H2O2 at physiological pH (7.4). Scanning Electron Microscopy was performed for physical characterization of the modified electrodes using pencil graphite electrodes. The active surface area for Pd/PTH-modified GCE was calculated as 1.103 cm2. The linear concentration range was determined as 0.2-7.0 mM and its sensitivity was determined as 40.0 µA mM-1. The detection limit (LOD) of the sensor was calculated as 12.3 µM with a signal/noise ratio of 3. [ABSTRACT FROM AUTHOR]

In the current study, silver nanoparticles doped polymethylmethacrylate (Ag/PMMA) nanocomposite was created not using any enzyme, checked for glucose detection. Firstly, chemical reduction method was employed to make the silver nanoparticles and secondly, the silver nanoparticles were mixed with PMMA via solution casting and sonication method to obtain the binary nanocomposite of Ag/PMMA. The morphology imaging and physical properties of Ag/PMMA nanocomposite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and Fourier transform infrared spectroscopy (FTIR). In order to build an electrochemical sensor, a glassy carbon (GC) electrode was altered with Ag/PMMA, and our findings showed that the custom-made electrode displayed electrocatalytic performance for the detection of glucose (C6H12O6) in 0.1 M solution of phosphate buffer (PBS, pH = 7.0). Voltammetric and amperometric sensors for the electrochemical detection of glucose were created based on these altered electrodes. The range of the voltammetric sensor was linear (from 0.1 to 1 mM) and high sensitivity of 41 µA mM−1 cm−2. [ABSTRACT FROM AUTHOR]

Conducting polymers are used in a wide range of applications, especially in the design and development of electrochemical sensors. Their main advantage, in this context, is their ability to efficiently modify an electrode surface using the direct polymerization of a suitable monomer in an electrochemical cell, or by physical coating. Additionally, the conducting polymers can be mixed with further materials (metal nanoparticles, carbonaceous materials) to enhance conductivity and analytical features (linear range, limit of detection, sensitivity, and selectivity). Due to their characteristics, conducting polymer-based amperometric sensors are applied to the determination of different organic and inorganic analytes. A view of recent advances in this field focusing on pyrrole, thiophene, and 3,4-ethylenedioxythiophene as starting materials is reported. [ABSTRACT FROM AUTHOR]

Galactose monitoring in individuals allows the prevention of harsh health conditions related to hereditary metabolic diseases like galactosemia. Current methods of galactose detection need development to obtain cheaper, more reliable, and more specific sensors. Enzyme-containing amperometric sensors based on galactose oxidase activity are a promising approach, which can be enhanced by means of their inclusion in a redox polymer coating. This strategy simultaneously allows the immobilization of the biocatalyst to the electroactive surface and hosts the electron shuttling units. An additional deposition of capping polymers prevents external interferences like ascorbic or uric acid as well as biofouling when measuring in physiological fuels. This work studies the protection effect of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate (MPC) and polyvinylimidazole-polysulfostyrene (P(VI-SS)) when incorporated in the biosensor design for the detection of galactose in human plasma. [ABSTRACT FROM AUTHOR]

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM−1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors. [ABSTRACT FROM AUTHOR]

The measurement of hydrogen isotopes will be of great interest for future fusion reactors to ensure their proper operation. For this reason, electrochemical sensors will be suitable tools for hydrogen isotopes quantification, as they can perform on-line and in situ measurements. One of the many challenges in hydrogen sensing is finding materials suitable for use at high temperatures and in aggressive environments. In this regard, perovskite-type ceramics exhibit high proton conductivity and excellent physical and chemical stabilities. These properties make perovskite materials ideal candidates for the development of high-temperature hydrogen isotopes sensors. In this study, BaCe 0.6 Zr 0.3 Y 0.1 O 3-α electrolyte was employed to fabricate amperometric sensors to monitor hydrogen isotopes. First, the ionic conductivity of the electrolyte was measured for hydrogen and deuterium using Electrochemical Impedance Spectroscopy (EIS) in order to determine isotopic effects. It was observed a protonic conduction as the governing transport mechanism. In addition, the ratio between the ionic conductivity of hydrogen and deuterium was 1.2–1.4. Then, amperometric measurements were performed at 350, 400, and 500 °C, while maintaining a voltage of 0.15 V between electrodes. The sensors' performance was assessed for hydrogen and deuterium partial pressures ranging from 0.15 to 0.30 mbar within an argon atmosphere. Calibration curves for both isotopes exhibited differences of approximately 20% in their slopes, which agrees with the trend observed in the ionic conductivity results. Additionally, the response time to hydrogen was three times faster compared to that observed for deuterium. These findings suggest that electrochemical sensors utilizing solid-state electrolytes, such as BaCe 0.6 Zr 0.3 Y 0.1 O 3-α , holds great promise as an innovative and effective tool for hydrogen isotope sensing. [Display omitted] • Hydrogen and deuterium isotopic effect was studied on BaCe 0.6 Zr 0.3 Y 0.1 O 3-α (BCZY) electrolyte. • BCZY ionic conductivity was measured for H 2 and D 2 from 150 to 500 °C. D 2 showed a 20% reduction when compared to H 2. • The factors from the Arrhenius equation showed H+ to have greater ease of movement within BCZY compared to D+. • Difference in sensitivity of about 20 % was detected between H 2 and D 2 during amperometric measurements. [ABSTRACT FROM AUTHOR]

In this study, we produced a nanocomposite composed of Ni-Pd bimetallic nanoparticles with precise morphologies that are adorned on multiwall carbon nanotubes. Electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the produced material. FE-SEM and HR-TEM analysis confirmed the uniform distribution of Ni-Pd across f-MWCNT surfaces. The findings reveal that incorporating Ni-Pd nanoparticles on the surface of f-MWCNT can improve catalytic activity over Ni NPs. The manufactured electrode has garnered a lot of interest in detecting and quantifying dopamine because of its demonstrated potential for instantaneous response, real-time measurements, increased selectivity, and sensitivity. Dopamine (DA) electrochemical activity in the presence of phosphate buffer solution (PBS) as an electrolyte at pH 7 was tested utilizing CV, DPV, and amperometry techniques to explore the sensor's performance. The finding presented here reveals a simple strategy for creating a modified electrode. The Ni-Pd/f-MWCNT-modified electrode sensor reveals a wide linear range of dopamine (2–400 µM), with a limit of detection (LOD) 0.05 µM, limit of quantification (LOQ) 0.166 µM, and sensitivity 2.116 µA/µM cm2. [ABSTRACT FROM AUTHOR]

A diffusion model for the analysis of chronoamperometric data in response to a concentration step is developed for amperometric gas sensors. This analysis avoids the difficulties with standard potentiodynamic measurements at the large specific area, high capacitance electrodes employed in these sensors. Despite the fact that typical devices comprise multiple layers with varying thicknesses and diffusivities, we show that typical chronoamperometric traces can be fitted to a simple diffusion model with a single parameter τ=L2D ${\tau ={{{L}^{2}}\over{D}}}$ where L is an overall effective thickness of the diffusion barrier and D is an effective diffusion coefficient. Through a comparison of the transient and steady‐state current, independent estimates of L and D in the devices can be made. The model is also extended to cover cases with interfacial kinetic barriers; such kinetic limitations lead to a change in the effective values L and D, but the simple diffusion model remains a good fit to the data. This analysis shows that transient sensor responses can be characterised by a single parameter τ and conversely that deviations from this regression model cannot be assigned to (i) complex layer architectures or (ii) interlayer kinetic barriers. Instead, we show that non‐uniform accessibility effects arising from a distribution of diffusion rates across the device lead to deviations from the simple regression model, but that they may be captured approximately by a more complex model in which τ has a probability distribution. [ABSTRACT FROM AUTHOR]

The positive effects of polyphenolic compounds on the sensory characteristics of wine and human health indicate a great need for a simple, fast and easily accessible method to determine the content of polyphenols in wine. The aim of this study is the electrochemical characterization of polyphenolic compounds in natural wine samples using a modified carbon paste electrode with TiO2 nanoparticles (MCPE/npTiO2) and improved voltammo­gram processing to obtain indicative data for polyphenols. The most marked influence of the modification of CPE with TiO2 nanoparticles was an increased sensitivity to electrooxi­dation, which is reflected in an increase of the anodic peak current. Of the five tested poly­phenols, i.e., gallic acid (GA), caffeic acid (CA), catechin (CT), quercetin (QV) and resveratrol (RE), the current maximum of the first two oxidation peaks increased only for GA by a factor of about 2 and for CT by a factor of about 1.5. Of the three red wines, Vranac (VR), Merlot (ME), Cabernet Sauvignon (CS); three white wines, Graševina (GR), Temjanika (TE), Char­donnay (CS) and one rose wine, Belrose Mediterranée Rosé (RO) tested, an increase by a factor of about 2.5 was observed for two red wines (VR, CS) and by a factor of 1.5 for one red wine (ME), one white wine (GR), and the rose wine (RO), while no increase in the current signal was observed for one of the white wines (CS). The most significant increase in the voltam­metric signal of GA at the MCPE/npTiO2 compared to other studied polyphenols can be explained by its higher affinity for adsorption on TiO2 nanoparticles. The investigated modified electrode provides an improved, linear and reproducible voltammetric response in wine samples. Consequently, MCPE/npTiO2 represents a good basis for the further deve­lopment of an integrated sensor/data system with the possibility of a broader application for the detection of polyphenols, especially GA, as an aroma and visually relevant parameter in winemaking.

This work presents a novel compact CMOS potentiostat-designed circuit for an electrochemical cell. The proposed topology functions as a circuit interface, controlling the polarization of voltage signals at the sensor electrodes and facilitating current measurement during the oxidation–reduction process of an analyzed solution. The potentiostat, designed for CMOS technology, comprises a two-stage amplifier, two current mirror blocks coupled to this amplifier, and a CMOS push–pull output stage. The electrochemical method of cyclic voltammetry is employed, operating within a voltage range of ±0.8 V and scan rates of 10 mV/s, 25 mV/s, 100 mV/s, and 250 mV/s. The circuit is capable of reading currents ranging from 10 µA to 500 µA. Experimental results were obtained using a potassium ferrocyanide K3[Fe(CN)6] redox solution with concentrations of 10, 15, and 20 mmol/L, and their corresponding voltammograms were evaluated. The experimental results from a discrete circuit demonstrate that the proposed potentiostat topology produces outcomes consistent with those of classical topologies presented in the literature and industrial equipment.

The Amperometric Gas Sensor (AGS) uses an electrode as the transducer element which converts its signal into a current from the electrochemical reaction of analytes taking place at the electrode surface. Many attempts to improve AGS performance, such as modifying the working electrode, applying a particular gas-permeable membrane, and selecting the proper electrolyte, etc., have been reported in the scientific literature. On the other hand, in the materials community, atomic gold has gained much attention because its physicochemical properties dramatically differ from those of gold nanoparticles. This paper provides an overview of the use of atomic gold in AGSs, both in a bulky AGS and a miniaturized AGS. In the miniaturized AGS, the system must be redesigned; for example, the aqueous electrolyte commonly used in a bulky AGS cannot be used due to volatility and fluidity issues. A Room Temperature Ionic Liquid (RTIL) can be used to replace the aqueous electrolyte since it has negligible vapor pressure; thus, a thin film of RTIL can be realized in a miniaturized AGS. In this paper, we also explain the possibility of using RTIL for a miniaturized AGS by incorporating a quartz crystal microbalance sensor. Several RTILs coated onto modified electrodes used for isomeric gas measurement are presented. Based on the results, the bulky and miniaturized AGS with atomic gold exhibited a higher sensor response than the AGS without atomic gold. [ABSTRACT FROM AUTHOR]

The aim of this work was to explore the possibility of using a Cu-exchanged zeolitic volcanic tuff (which is natural and easy to prepare and apply) for the preparation of a new low-cost carbon paste amperometric sensor for H2O2 detection. The properties of the zeolitic volcanic tuff were determined using chemical analysis, energy-dispersive X-ray spectroscopy, the specific surface area, electron microscopy, X-ray diffraction spectroscopy, and Fourier-transform infrared spectroscopy. The sensor was successfully built and operates at pH 7, at an applied potential of −150 mV Ag/AgCl/KClsat, presenting a sensitivity of 0.87 mA M−1, a detection limit of 10 µM and a linear domain up to 30 mM H2O2. These good electroanalytic parameters for H2O2 detection (a low detection limit and high sensitivity) support the possibility of using these sensors for the detection of many analytes in environmental, food and medical applications. [ABSTRACT FROM AUTHOR]

Vitamins are one of the most essential organic compounds that are necessary for the human body, in order to develop and grow in a healthy way. The aim of this mini-review is to bring together a series of electrochemical sensors (voltametric and amperometric) developed for the determination of vitamins from the families of B, D and K in biological, pharmaceutical or food-related samples. For this mini-review, 16 articles published between 2016 and 2021 were taken into consideration. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the development of a hydrazine sensor using gold nanoparticles (AuNPs) electrodeposited on the surface of a glassy carbon electrode (GCE) modified with the material composite of graphene oxide (GO) and poly(3,4-ethylenedioxythiophene):poly(styrenes ulfonate) (PEDOT:PSS). The morphological, electrochemical, and structural properties of this developed hydrazine sensor were characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Cyclic voltammetry and amperometry techniques have been used to investigate the electrochemical behavior and electroanalytical performance of this proposed sensor, and obtained an excellent result in terms of its analytical parameters. A linear range of 0.2-100 µM was obtained from the amperometric detection of hydrazine using this developed sensor. The detection and quantitation limits of this proposed hydrazine sensor were calculated as 0.005 and 0.08 µM, respectively. Furthermore, this proposed sensor for hydrazine detection exhibited good reproducibility and stability with a relative standard deviation (%RSD) of less than 5%. In addition, this developed sensor for hydrazine detection also exhibited good selectivity in the presence of several interferences, including NaNO2, FeSO4, Zn(CH3CO2)2, NH4NO3, chlorophenol, triclosan, and ascorbic acid, as well as it depicted %recovery values of 93-104%. In conclusion, this platform sensing based on a AuNPs/GO/PEDOT:PSS-modified GCE for hydrazine detection shows excellent electroanalytical performance and could potentially be employed for real applications. [ABSTRACT FROM AUTHOR]

In this study, we measured the enzymatic activity of acetylcholinesterase (AChE) using the Light Addressable Amperometric Sensor (LAAS), an electrochemical sensor that can easily measure redox current values of multiple samples. Acetylthiocholine (ATCh) was used as a substrate. ATCh is hydrolyzed by AChE and releases electrons, making it possible to measure current values in accordance with the amount of substrate using LAAS. When KCl solution was used as the supporting electrolyte and an Ag/AgCl reference electrode as the counter electrode, a correlation between substrate concentration and reaction was confirmed in the range of 1 μM–10 mM. Malathion was then used as an inhibitor of AChE. Malathion phosphorylates and inactivates AChE, which prevents substrate hydrolysis and is expected to decrease the current value. Experimental results showed a decrease in sensor response correlated with inhibitor concentration. [ABSTRACT FROM AUTHOR]

New modified electrode materials, based on a combination of hybrid nanocomposites such as magnetic nanoparticles, inorganic polymer (SiO2) and different types of organic polymers, were studied. Three types of organic polymers were used in order to find the effect that each of polymers has on the electrochemical properties of the final material. The electrochemical properties of the synthesised materials were investigated, the best electrochemical response was for pAAc covered nanoparticles compared to the other three tested materials. This favourable electrochemical response effect is due to the fact that in case of this material we succeed in obtaining a very uniform coverage of the polymeric shell with a favourable hydrogel structure and thicknesses which is perfectly suitable for adsorption of a relatively high concentration of TB in a very easi and homogenous way. By electrochemical measurements it was proved that this electrode presents electro-catalytic effect towards nitrite oxidation and can be used for nitrite detection. By comparing with other electrodes, the electro-catalytic effect of MNPs-SiO2-pAAc is better because the nitrite oxidation peak appears in this case at a potential closer to 0 mV vs. Ag/AgCl/KClsat, which is favourable to avoid interferences in amperometric nitrite detection in real samples. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor was developed for the detection of Epinephrine (EP) utilizing Azure A (AzA), a phenothiazine dye, and citrate-capped silver nanoparticles. The interaction between Azure A and silver nanoparticles facilitated the formation of AzA/silver nanoclusters through a self-assembled approach. The morphological analysis of AzA/silver nanoclusters was conducted using field-emission scanning electron microscopy (FESEM). The nanoclusters were then immobilized on a graphite electrode via a simple drop-casting method, resulting in a modified electrode. The electrochemical properties of the modified electrode were investigated using cyclic voltammetry and linear sweep voltammetry techniques. The modified electrode exhibited enhanced electrocatalytic oxidation of EP at a lower oxidation potential of 0.27 V. The electrochemical analysis demonstrated that the modified electrode functioned as an amperometric sensor, enabling the detection of EP within a concentration range of 4.6 × 10–7 to 3.6 × 10–3 M, with a correlation coefficient of 0.9950 and a detection limit of 2.2 × 10–7 M (S/N = 3). The modified electrode exhibited excellent selectivity, sensitivity, and a remarkably low detection limit, making it highly suitable for EP determination. Its ease of preparation further adds to the practicality and potential applications of this electrode. [ABSTRACT FROM AUTHOR]

An unusual strategy was designed to fabricate conductive patterns for flexible surfaces, which were utilized for non-enzymatic amperometric glucose sensors. The Ag/AgCl/Ag quasi-reference ink formulation utilized two reducing agents, NaBH 4 and ethylene glycol. The parameters of the ink, such as sintering time and temperature, NaBH 4 concentration, and layer number of coatings on flexible laser-induced graphene (LIG) electrodes were investigated. The conductive Ag/AgCl/Ag ink was characterized using electrochemical and surface analysis techniques. The electrocatalytic activity of Ag/AgCl/Ag NRs can be attributed to their high surface area, which offer numerous active sites for catalytic reactions. The selectivity and sensitivity of the electrodes for glucose detection were investigated. The XRD analysis showed (200) oriented AgCl on covered Ag NRs, and with the addition of NaBH 4 , the intensity of the peaks of the Ag NRs increased. The wide linear range of non-enzymatic sensors was attained from 0.003 to 0.18 mM and 0.37 to 5.0 mM, with a low limit of detection of 10 μ M and 20 μ M, respectively.The linear range of enzymatic sensor in real sample was determined from 0.040 to 0.097 mM with a detection limit of 50 μ M. Furthermore, results of the interference studies demonstrated excellent selectivity of the Ag/AgCl/Ag NRs/LIG electrode. The Ag/AgCl/Ag NRs on the flexible LIG electrode exhibited excellent sensitivity,long-time stablity,and reproducibility. The efficient electroactivity were deemed suitable for various electrochemical applications and biosensors. [ABSTRACT FROM AUTHOR]

In this work, we report a non‐enzymatic and metal‐free ethanol sensor based on 3D PLA‐graphene electrodes. We evaluated the optimal activation treatment for PLA‐graphene to achieve a sensor for monitoring ethanol levels in saliva samples, following the legal limits for drivers in various countries. The analytical performance of the sensor was determined through amperometric measurements, demonstrating a linear detection ranging supporting electrolyte (0.990–19.3 mmol L−1) and artificial saliva sample (0.990–17.4 mmol L−1), with respective limits of detection of 0.135 and 0.239 mmol L−1. The 3D‐printed sensor exhibited excellent repeatability and reproducibility. This method was effectively employed for ethanol detection, highlighting its potential as an alternative approach for assessing ethanol levels in drivers while considering diverse legal regulations across different countries. [ABSTRACT FROM AUTHOR]

The determination of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) play critical roles in chemical, environmental, and biological processes. In this study, non-enzymatic dual sensors for the simultaneous amperometric determination of NADH and H2O2 were prepared based on a dual screen-printed carbon electrode (DSPCE) modified with reduced graphene oxide (RGO), polyneutral red (PNR), and gold nanoparticles (AuNP). The DSPCE/RGO/PNR/AuNP electrode was characterized by cyclic voltammetry and scanning electron microscopy. RGO/PNR/AuNP materials showed an electrocatalytic effect on the electrooxidation of NADH and the electroreduction of H2O2. Simultaneous amperometric determination of NADH and H2O2 was performed at + 0.15 V and − 0.45 V, respectively. The developed dual sensor allowed the simultaneous determination of both analytes in fast, high repeatability and sensitivity (2.28 µA mM−1 for NADH and 2.70 µA mM−1 for H2O2) and a low limit of detection (5.53 µA for NADH and 8.35 µA for H2O2). The application stability of the dual sensor was tested for 45 days. The simultaneous determination of NADH and H2O2 in blood serum was performed using the fabricated non-enzymatic dual sensor, and high recoveries were obtained. The developed disposable dual sensors can be used in point-of-care tests for simultaneous amperometric determination of NADH and H2O2. A disposable non-enzymatic dual sensor for simultaneous amperometric determination of NADH and H2O2 [ABSTRACT FROM AUTHOR]

The determination of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) play critical roles in chemical, environmental, and biological processes. In this study, non-enzymatic dual sensors for the simultaneous amperometric determination of NADH and H2O2 were prepared based on a dual screen-printed carbon electrode (DSPCE) modified with reduced graphene oxide (RGO), polyneutral red (PNR), and gold nanoparticles (AuNP). The DSPCE/RGO/PNR/AuNP electrode was characterized by cyclic voltammetry and scanning electron microscopy. RGO/PNR/AuNP materials showed an electrocatalytic effect on the electrooxidation of NADH and the electroreduction of H2O2. Simultaneous amperometric determination of NADH and H2O2 was performed at + 0.15 V and − 0.45 V, respectively. The developed dual sensor allowed the simultaneous determination of both analytes in fast, high repeatability and sensitivity (2.28 µA mM−1 for NADH and 2.70 µA mM−1 for H2O2) and a low limit of detection (5.53 µA for NADH and 8.35 µA for H2O2). The application stability of the dual sensor was tested for 45 days. The simultaneous determination of NADH and H2O2 in blood serum was performed using the fabricated non-enzymatic dual sensor, and high recoveries were obtained. The developed disposable dual sensors can be used in point-of-care tests for simultaneous amperometric determination of NADH and H2O2. A disposable non-enzymatic dual sensor for simultaneous amperometric determination of NADH and H2O2 [ABSTRACT FROM AUTHOR]

This paper presents a novel modified electrode for an amperometric hydrazine sensor based on multi-walled carbon nanotubes (MWCNTs) modified with lignosulfonate (LS) and decorated with palladium nanoparticles (NPds). The MWCNT/LS/NPd hybrid was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The electrochemical properties of the electrode material were evaluated using cyclic voltammetry and chronoamperometry. The results showed that GC/MWCNT/LS/NPd possesses potent electrocatalytic properties towards the electro-oxidation of hydrazine. The electrode demonstrated exceptional electrocatalytic activity coupled with a considerable sensitivity of 0.166 μA μM−1 cm−2. The response was linear from 3.0 to 100 µM L−1 and 100 to 10,000 µM L−1, and the LOD was quantified to 0.80 µM L−1. The efficacy of the modified electrode as an electrochemical sensor was corroborated in a study of hydrazine determination in water samples. [ABSTRACT FROM AUTHOR]

Melatonin (MT), a pineal gland hormone, regulates the sleep/wake cycle and is a potential biomarker for neurodegenerative disorders, depression, hypertension, and several cancers, including prostate cancer and hepatocarcinoma. The amperometric detection of MT was achieved using a sensor customized with ruthenium-incorporated carbon spheres (Ru–CS), possessing C- and O-rich catalytically active Ru surfaces. The non-covalent interactions and ion–molecule adducts between Ru and CS favor the formation of heterojunctions at the sensor–analyte interface, thus accelerating the reactions towards MT. The Ru–CS/Screen-printed carbon electrode (SPCE) sensor demonstrated the outstanding electrocatalytic oxidation of MT owing to its high surface area and heterogeneous rate constants and afforded a lower detection limit (0.27 μM), high sensitivity (0.85 μA μM −1 cm−2), and excellent selectivity for MT with the co-existence of crucial neurotransmitters, including norepinephrine, epinephrine, dopamine, and serotonin. High concentrations of active biomolecules, such as ascorbic acid and tyrosine, did not interfere with MT detection. The practical feasibility of the sensor for MT detection in pharmaceutical samples was demonstrated, comparable to the data provided on the product labels. The developed amperometric sensor is highly suitable for the quality control of medicines because of its low cost, simplicity, small sample size, speed of analysis, and potential for automation. [ABSTRACT FROM AUTHOR]

Universal platforms to analyze biomolecules using sensor devices can address critical diagnostic challenges. Sensor devices like electrical-based field-effect transistors play an essential role in sensing biomolecules by charge probing. Graphene-based devices are more suitable for these applications. It has been previously reported that Graphene Field-Effect Transistor (GFET) devices detect DNA hybridization, pH sensors, and protein molecules. Graphene became a promising material for electrical-based field-effect transistor devices in sensing biomarkers, including biomolecules and proteins. In the last decade, FET devices have detected biomolecules such as DNA molecules, pH, glucose, and protein. These studies have suggested that the reference electrode is placed externally and measures the transfer characteristics. However, the external probing method damages the samples, requiring safety measurements and a substantial amount of time. To control this problem, the graphene field-effect transistor (GFET) device is fabricated with an inbuilt gate that acts as a reference electrode to measure the biomolecules. Herein, the monolayer graphene is exfoliated, and the GFET is designed with an in-built gate to detect the Interleukin-6 (IL-6) protein. IL-6 is a multifunctional cytokine which plays a significant role in immune regulation and metabolism. Additionally, IL-6 subsidizes a variability of disease states, including many types of cancer development, and metastasis, progression, and increased levels of IL-6 are associated with a higher risk of cancer and can also serve as a prognostic marker for cancer. Here, the protein is desiccated on the GFET device and measured, and Dirac point shifting in the transfer characteristics systematically evaluates the device's performance. Our work yielded a conductive and electrical response with the IL-6 protein. This graphene-based transducer with an inbuilt gate gives a promising platform to enable low-cost, compact, facile, real-time, and sensitive amperometric sensors to detect IL-6. Targeting this pathway may help develop treatments for several other symptoms, such as neuromyelitis optica, uveitis, and, more recently, COVID-19 pneumonia. [ABSTRACT FROM AUTHOR]

Conducting polymers are used in a wide range of applications, especially in the design and development of electrochemical sensors. Their main advantage, in this context, is their ability to efficiently modify an electrode surface using the direct polymerization of a suitable monomer in an electrochemical cell, or by physical coating. Additionally, the conducting polymers can be mixed with further materials (metal nanoparticles, carbonaceous materials) to enhance conductivity and analytical features (linear range, limit of detection, sensitivity, and selectivity). Due to their characteristics, conducting polymer-based amperometric sensors are applied to the determination of different organic and inorganic analytes. A view of recent advances in this field focusing on pyrrole, thiophene, and 3,4-ethylenedioxythiophene as starting materials is reported.

The present invention describes a novel flexible nanosensor for the electrochemical detection of uric acid (UA) present in urine. The synthesized graphite-boron nanocomposite with an average thickness of ∼32 nm was grown up on a flexible polyvinylidene fluoride film with an average thickness of ∼50 μm and it acts as a nonenzymatic sensor for UA. The developed flexible sensor showed a prominent reduction peak in cyclic voltammetry and amperometric response with the presence of different concentrations of aqueous UA solution. In the electrochemical study, the redox peak was generated near ∼−0.42 V with a detection limit of around ∼2.09 μM as the bottom level. The high robustness of the developed sensor originated from the polymeric film base and the rapid response time of ∼0.5 s for detecting UA present in human urine. The interference property of the sensor was confirmed in the presence of bilirubin and creatinine as an eventual reference toward selectivity. The phase and morphology of the sensor surface were extensively observed before and after sensing to comprehend the electrochemical interaction between the sensor and target molecules. The generated quantitative results of the integrated system were verified by testing known and unknown concentrations of UA solutions. [ABSTRACT FROM AUTHOR]

A hydrogen concentration measurement device is developed for nuclear reactor primary circuits water. Despite the necessity to monitor hydrogen, only one producer offers a really selective hydrogen sensor on the world market because of the complexity of the device preparation when long‐term signal stability is required. Therefore, the Mass Transfer Laboratory at UCT Prague shares the experience gained during the sensor development. The results of the amperometric hydrogen sensor laboratory tests are presented, which demonstrate how to improve the sensor durability. An operational test in Dukovany nuclear power plant confirmed a significant improvement of the latest sensor version and showed that a simple principle could be realized in the form of a reliable device for industrial measurements. [ABSTRACT FROM AUTHOR]

An amperometric sensor based on CaZr0.95Sc0.05O3−δ (CZS) proton-conducting oxide for the measurement of hydrogen concentration in air was designed and tested. Dense CZS ceramics were fabricated through uniaxial pressing the powder synthesized by the solid-state method and sintering at 1650 °C for 2 h. The conductivity of CZS was shown to increase with increasing air humidity, which indicates the proton type of conductivity. The sensor was made from two CZS plates, one of which had a cavity was drilled to form an inner chamber, that were then pressed against each other and sealed around the perimeter to prevent gas leaking. The inner chamber of the sensor was connected with the outer atmosphere via an alumina ceramic capillary, which acted as a diffusion barrier. The sensor performance was studied in the temperature range of 600–700 °C in the mixtures of air with hydrogen. The sensor signal, or the limiting current, was found to linearly increase with the hydrogen concentration, which simplifies the sensor calibration. The sensor demonstrated a high sensitivity of ~60 μA per 1% H2 at 700 °C, a fast response, high reproducibility, good selectivity, and long-term stability. [ABSTRACT FROM AUTHOR]

The ultimate objective of this research work is to design a sensitive and selective electrochemical sensor for the efficient detection of ascorbic acid (AA), a vital antioxidant found in blood serum that may serve as a biomarker for oxidative stress. To achieve this, we utilized a novel Yb2O3.CuO@rGO nanocomposite (NC) as the active material to modify the glassy carbon working electrode (GCE). The structural properties and morphological characteristics of the Yb2O3.CuO@rGO NC were investigated using various techniques to ensure their suitability for the sensor. The resulting sensor electrode was able to detect a broad range of AA concentrations (0.5–1571 µM) in neutral phosphate buffer solution, with a high sensitivity of 0.4341 µAµM−1cm−2 and a reasonable detection limit of 0.062 µM. The sensor's great sensitivity and selectivity allowed it to accurately determine the levels of AA in human blood serum and commercial vitamin C tablets. It demonstrated high levels of reproducibility, repeatability, and stability, making it a reliable and robust sensor for the measurement of AA at low overpotential. Overall, the Yb2O3.CuO@rGO/GCE sensor showed great potential in detecting AA from real samples. [ABSTRACT FROM AUTHOR]

A simple, rapid, cost‐effective and non‐enzymatic amperometric sensor for sensitive and simultaneous determination of uric acid (UA), dopamine (DA), and ascorbic acid (AA) was developed based on a new combination of carbon black (CB) and molybdenite (MLN) modified glassy carbon electrode (GCE). The synergistic effect of CB and MLN can increase electrode's conductivity, accelerate the electrochemical catalytic reaction and enhance the oxidation currents of UA, DA and AA. Cyclic voltammetry demonstrated the sensor to perform excellently in the electrochemical oxidation of AA, DA and UA, respectively. The oxidation potentials are well separated (oxidation peaks at −50 mV, 200 mV and 350 mV vs. Ag/AgCl) for AA, DA and UA with the detection limits of 5 μmol/L, 8.7 μmol/L and 9 μmol/L (S/N=3), respectively. The MLN‐CB/GCE sensor also demonstrated superior electrochemical properties including good stability, selectivity and reproducibility. In addition, the prepared sensor for UA allowed the determination of UA in highly diluted body fluids (urine), and the analytical results obtained by the present sensor were in good agreement with those obtained by conventional spectrophotometry. [ABSTRACT FROM AUTHOR]

Miniaturized sensors possess many advantages, such as rapid response, easy chip integration, a possible lower concentration of target compound detection, etc. However, a major issue reported is a low signal response. In this study, a catalyst, the atomic gold clusters of Aun where n = 2, was decorated at a platinum/polyaniline (Pt/PANI) working electrode to enhance the sensitivity of butanol isomers gas measurement. Isomer quantification is challenging because this compound has the same chemical formula and molar mass. Furthermore, to create a tiny sensor, a microliter of room-temperature ionic liquid was used as an electrolyte. The combination of the Au2 clusters decorated Pt/PANI and room temperature ionic liquid with several fixed electrochemical potentials was explored to obtain a high solubility of each analyte. According to the results, the presence of Au2 clusters increased the current density due to electrocatalytic activity compared to the electrode without Au2 clusters. In addition, the Au2 clusters on the modified electrode had a more linear concentration dependency trend than the modified electrode without atomic gold clusters. Finally, the separation among butanol isomers was enhanced using different combination of room-temperature ionic liquids and fixed potentials. [ABSTRACT FROM AUTHOR]

The rapid and straightforward detection of formaldehyde (FA) in the environment is crucial for preventing the accidental inhalation of FA and limiting skin exposure to FA. In this study, we developed a simple nickel‐based electrocatalytic electrode on carbon nanofibers (CNFs−Ni), which is suitable for rapidly detecting FA at room temperature. Centrifugal electrospinning was used to obtain polyacrylonitrile (PAN) nanofibers, which was subsequently stabilized and carbonized to fabricate the CNFs. Carbonization of the CNFs occurred at various temperatures (Tc=1200, 1300, 1400, and 1500 °C). PAN CNFs served as a highly conductive template for electroless plating under a magnetic field of 500 G to grow acicular nickel. The amperometric responses of the CNFs−Ni to aqueous FA were then measured. A lab‐built amperometric gas sensor (CNFs−Ni 1–8), which comprised CNFs with a reduced Ni loading, was used as the electrode for detecting gaseous FA. Scanning electron microscopy (SEM), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry were used to evaluate the sensitivities of the electrodes. Within the linear range of 0.05–91.5 mM, the CNFs1400‐Ni electrode was highly sensitive for detecting aqueous FA (2592 μA mM−1 cm−2), as evidenced by the fast response time (6 s). At a low concentration of gaseous FA (0.5 ppm), the laboratory‐built FA gas sensor was stable (98.3 %) and had a fast response time (5 s) after 9 h of continuous operation. [ABSTRACT FROM AUTHOR]

With rapidly increasing environmental pollution, there is an urgent need for the development of fast, low-cost, and effective sensing devices for the detection of various organic and inorganic substances. Silver nanoparticles (AgNPs) are well known for their superior optoelectronic and physicochemical properties, and have, therefore, attracted a great deal of interest in the sensor arena. The introduction of AgNPs onto the surface of two-dimensional (2D) structures, incorporation into conductive polymers, or within three-dimensional (3D) nanohybrid architectures is a common strategy to fabricate novel platforms with improved chemical and physical properties for analyte sensing. In the first section of this review, the main wet chemical reduction approaches for the successful synthesis of functional AgNPs for electrochemical sensing applications are discussed. Then, a brief section on the sensing principles of voltammetric and amperometric sensors is given. The current utilization of silver nanoparticles and silver-based composite nanomaterials for the fabrication of voltammetric and amperometric sensors as novel platforms for the detection of environmental pollutants in water matrices is summarized. Finally, the current challenges and future directions for the nanosilver-based electrochemical sensing of environmental pollutants are outlined. [ABSTRACT FROM AUTHOR]

Amperometric sensors evaluate current changes that occur as a result of redox reactions under constant applied potential. These changes in current intensity are stoichiometrically related to the concentration of analytes. Owing to their unique features, such as fast reaction velocity, high specificity, abundant existence in nature, and feasibility to be immobilized, enzymes are widely used by researchers to improve the performance of amperometric sensors. Unfortunately, natural enzymes have intrinsic disadvantages due to their protein structures. To overcome these proteinic drawbacks, scientists have developed nanozymes, which are nanomaterials with enzymatic properties. As the result of significant advances in materiology and analytical science, great progress has been achieved in the development of nanozyme-based amperometric sensors with outstanding performance. To highlight achievements made in recent years, we first summarize the development directions of nanozyme-based amperometric sensors. Then, H2O2 sensors, glucose sensors, sensors combining natural enzymes with nanozymes, and sensors targeting untraditional specific targets will be introduced in detail. Finally, the current challenges regarding the nanozymes utilized in amperometric sensors are discussed and future research directions in this area are suggested. [ABSTRACT FROM AUTHOR]