Constant Potential Amperometry Research Articles

Electrochemical Detection of Bisphenol A Based on Gold Nanoparticles/Multi-Walled Carbon Nanotubes: Applications on Glassy Carbon and Screen Printed Electrodes.

Bisphenol A (BPA) has been classified as an endocrine-disrupting substance that may cause adverse effects on human health and the environment. The development of simple and sensitive electrochemical biosensors is crucial for the rapid and effective quantitative determination of BPA. This work presents a study on electrochemical sensors utilizing gold nanoparticle-modified multi-walled carbon nanotubes (CNT/AuNPs). Glassy carbon electrodes (GCEs) and screen-printed electrodes (SPEs) were conveniently modified and used for BPA detection. AuNPs were electrodeposited onto the CNT-modified electrodes using the galvanostatic method. The electrodes were properly modified and characterized by using Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance analysis (EIS). The electrochemical response of the sensors was studied using differential pulse voltammetry (DPV) and constant potential amperometry (CPA) for modified GCE and SPE electrodes, respectively, and the main analytical parameters were studied and optimized. Problems encountered with the use of GCEs, such as sensor degradation and high limit of detection (LOD), were overcome by using modified SPEs and a flow injection device for the measurements. Under this approach, an LOD as low as 5 nM (S/N = 3) was achieved and presented a linear range up to 20 μM. Finally, our investigation addressed interference, reproducibility, and reusability aspects, successfully identifying BPA in both spiked and authentic samples, including commercial and tap waters. These findings underscore the practical applicability of our method for accurate BPA detection in real-world scenarios. Notably, the integration of SPEs and a flow injection device facilitated simplified automation, offering an exceptionally efficient and reliable solution for precise BPA detection in water analysis laboratories.

Sustainable Electropolymerization of Zingerone and Its C2 Symmetric Dimer for Amperometric Biosensor Films.

Polymeric permselective films are frequently used for amperometric biosensors to prevent electroactive interference present in the target matrix. Phenylenediamines are the most commonly used for the deposition of shielding polymeric films against interfering species; however, even phenolic monomers have been utilized in the creation of these films for microsensors and biosensors. The purpose of this paper is to evaluate the performances of electrosynthesized polymers, layered by means of constant potential amperometry (CPA), of naturally occurring compound zingerone (ZING) and its dimer dehydrozingerone (ZING DIM), which was obtained by straight oxidative coupling reaction. The polymers showed interesting shielding characteristics against the main interfering species, such as ascorbic acid (AA): actually, polyZING exhibited an AA shielding aptitude comprised between 77.6 and 99.6%, comparable to that obtained with PPD. Moreover, a marked capability of increased monitoring of hydrogen peroxide (HP), when data were compared with bare metal results, was observed. In particular, polyZING showed increases ranging between 55.6 and 85.6%. In the present work, the molecular structures of the obtained polymers have been theorized and docking analyses were performed to understand their peculiar characteristics better. The structures were docked using the Lamarckian genetic algorithm (LGA). Glutamate biosensors based on those polymers were built, and their performances were compared with biosensors based on PPD, which is the most widespread polymer for the construction of amperometric biosensors.

Intermittent pulse amperometry as an effective electrochemical assay of 4-nitrophenol

4-nitrophenol (4-NP) is a precursor of many industrial products and drugs, an environmental pollutant, and is used as a reporter molecule in many enzyme assays and disease biomarker screens. Accordingly, 4-NP analysis is a cross-disciplinary requirement, and we propose intermittent pulse amperometry (IPA) as an alternative to spectrophotometric methods. The sensor signal is acquired by applying 0.5 s pulses of 0.95 V once every 99.5 s during continuous amperometric recordings at 0 V resting potential to drive intermittent 4-NP detection at a diffusion-limited rate. With IPA, sensor surface fouling by polymerization of radical intermediates formed in the anodic oxidation process, which is a severe problem in constant-potential amperometry and voltammetry of phenols, is kept at acceptable minimum by restriction of the time at the potential that produces contamination. Complex potential profiles with electrochemical activation steps and/or electrolyte supplementation with anti-fouling agents are not required. Calibration plots are linear up to 500 μM with a sensitivity of 35 nA μM−1 and a practical detection limit of 10 μM. Model samples of 100 μM 4-NP were assessed with suitable recovery rates, and in a proof-of-principle test as electrochemical readout of an enzyme assay, IPA accurately reported the time course of enzymic release of 4-NP from GlcNAc-4NP, a synthetic substrate of glucosaminidases. Simplicity and high performance are the major features of the proposed electrochemical 4-NP testing, and unless the analytical target is present only at trace levels, the technique is a promising alternative for the evaluation of 4-NP, either as a solution component or as a reporter molecule in enzyme assays.

Electrochemical bioassay based on l-lysine-modified magnetic nanoparticles for Escherichia coli detection: Descriptive results and comparison with other commercial magnetic beads

This paper describes the synthesis and biofunctionalization of magnetic nanoparticles (MNPs) of about 10 nm obtained by the coprecipitation method under alkaline conditions. These homemade nanoparticles were conveniently modified with l -lysine and glutaraldehyde and used as solid support for the immunochemical determination of Escherichia coli . Biofunctionalized MNPs were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), and thermogravimetric analysis. Electrochemical detection was based on a sandwich Enzyme-Linked Immuno Magnetic Electrochemical (ELIME) method using a primary antibody (capture antibody, Ab1) and an HRP-labeled antibody (secondary, Ab-HRP). The enzymatic by-product was measured by constant potential amperometry. In the work described here, a quantitative determination of E. coli was achieved with a linear working range between 266 and 1 × 10 6 CFU mL −1 and a detection limit of ca. 80 CFU/mL. The sensitivity and the cross-reactivity of the proposed method against E. coli were tested using other commercial magnetic beads such as epoxy and undecaldehyde-modified MNPs and various potential interferences such as Pseudomonas aeruginosa, Enterococcus faecalis, Salmonella enterica, and Acinetobacter baumannii . The results showed similar analytical properties between the different commercial approaches and the homemade MNPs. This fact makes the MNP-Lys a very promising material for its integration into electrochemical sensing platforms. • Lysine-modified MNPs were synthesized and functionalized with glutaraldehyde. • MNPs were used in an Enzyme Linked Immuno Magnetic Electrochemical bioassay. • This approach allows the correct and selective detection of E. coli . • Electrochemical bioassay showed a limit of detection of ca. 80 CFU/mL • Our results were comparable to previous commercial approaches.

The Platinization of Graphite Composites Turns Widespread and Low-Cost Materials into Hydrogen Peroxide Sensors and High-Value Biosensor Transducers

Electrochemical microsensors and biosensors have been widely used in many fields, in particular neurochemical monitoring, because of their features. Usually, hydrogen peroxide (HP), obtained as a by-product of an enzymatic reaction, is the detected compound on transducers made of precious metals, in particular platinum. The over-time increase in the price of platinum and its alloys requires the use of miniaturizable low-cost supports that can be suitably modified with the deposition of Pt particles; among them, graphite is the most widespread. In the present paper, carbon-composition resistors (CCRs) and pencil leads (PLs) of different diameters (0.3, 0.5 and 2.0 mm), mainly made up of graphite, clay and some other components were used as carbonaceous support for the deposition of platinum. Platinizations were carried out by means of cyclic voltammetry (CV) and constant potential amperometry (CPA) techniques. On the platinized supports, hydrogen peroxide (HP) and ascorbic acid (AA) sensitivity were assessed in order to verify the possibility of using them as transducers of amperometric biosensors. All the used protocols determined the occurrence of HP monitoring, not appreciable on carbonaceous surfaces. We chose 0.3 mm Ø PLs for the construction of glucose biosensors by appropriately modifying the platinum surface layering, a permselective polymer, an enzyme booster, the glucose oxidase (GOx) enzyme and a containing network. The biosensor constructed in this way demonstrated a behavior comparable to that obtained using classic platinum wires.

Synergistic Distributed Thermal Regulation for On-CMOS High-Throughput Multimodal Amperometric DNA-Array Analysis

Accurate temperature regulation is critical for amperometric DNA analysis to achieve high fidelity, reliability, and throughput. In this work, a 9×6 cell array of mixed-signal CMOS distributed temperature regulators for on-CMOS multi-modal amperometric DNA analysis is presented. Three DNA analysis methods are supported, including constant potential amperometry (CPA), cyclic voltammetry (CV), and impedance spectroscopy (IS). In-cell heating and temperature sensing elements are implemented in standard CMOS technology without post-processing. Using proportional-integral-derivative (PID) control, the local temperature can be regulated to within ± 0.5∘C of any desired value between 20∘C and 90∘C. To allow the in-cell integration of independent PID control, a new mixed-signal design is proposed, where the two computationally intensive operations in the PID algorithm, multiplication, and subtraction, are performed by an in-cell dual-slope multiplying ADC, resulting in a small area and low power consumption. Over 95% of the circuit blocks are synergistically shared among the four operating modes, including CPA, CV, IS, and the proposed temperature regulation mode. A 3mm×3mm CMOS prototype fabricated in a 0.13μm CMOS technology has been fully experimentally characterized. The proposed distributed temperature regulation design and the mixed-signal PID implementation can be applied to a wide range of sensory and other applications.

Gold Nanospikes Formation on Screen-Printed Carbon Electrode through Electrodeposition Method for Non-Enzymatic Electrochemical Sensor

In this study, we reported the construction of Gold Nanospike (AuNS) structures on the surface of screen-printed carbon electrode (SPCE) used for non-enzymatic electrochemical detection. This modification was prepared with a one-step electrodeposition method by controlling the electrodeposition parameters, such as applied potential and deposition time, via Constant Potential Amperometry (CPA). Those parameters and precursor solution concentration were varied to investigate the optimum electrodeposition configuration. The results confirmed that AuNS were homogenously deposited and well-dispersed on the working electrode surface of SPCE. The AuNS-modified SPCE was implemented as a non-enzymatic sensor toward dopamine and could enhance the electrocatalytic ability compared with the bare SPCE. Further examination shows that the sensing performance of the AuNS-modified SPCE produced an increase in electrochemical surface area (ECSA) at 17.25 times higher than the bare electrode, a sensitivity of 0.056 µA mM−1 cm−2 with a wide linear range of 0.2–50 µM and a detection limit of 0.33 µM. In addition, AuNS-modified SPCE can selectively detect dopamine among other interfering analytes such as ascorbic acid, urea, and uric acid, which commonly coexist in the body fluid. This work demonstrated that AuNS-modified SPCE is a prospective sensing platform for non-enzymatic dopamine detection.

Biosensing Dopamine and L-Epinephrine with Laccase (Trametes pubescens) Immobilized on a Gold Modified Electrode.

Engineering electrode surfaces through the electrodeposition of gold may provide a range of advantages in the context of biosensor development, such as greatly enhanced surface area, improved conductivity and versatile functionalization. In this work we report on the development of an electrochemical biosensor for the laccase-catalyzed assay of two catecholamines—dopamine and L-epinephrine. Variety of electrochemical techniques—cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy and constant potential amperometry have been used in its characterization. It has been demonstrated that the laccase electrode is capable of sensing dopamine using two distinct techniques—differential pulse voltammetry and constant potential amperometry, the latter being suitable for the assay of L-epinephrine as well. The biosensor response to both catecholamines, examined by constant potential chronoamperometry over the potential range from 0.2 to −0.1 V (vs. Ag|AgCl, sat KCl) showed the highest electrode sensitivity at 0 and −0.1 V. The dependencies of the current density on either catecholamine’s concentration was found to follow the Michaelis—Menten kinetics with apparent constants KMapp = 0.116 ± 0.015 mM for dopamine and KMapp = 0.245 ± 0.031 mM for L-epinephrine and linear dynamic ranges spanning up to 0.10 mM and 0.20 mM, respectively. Calculated limits of detection for both analytes were found to be within the sub-micromolar concentration range. The biosensor applicability to the assay of dopamine concentration in a pharmaceutical product was demonstrated (with recovery rates between 99% and 106%, n = 3).

Development and Practical Application of Glucose Biosensor Based on Dendritic Gold Nanostructures Modified by Conducting Polymers.

In this study, graphite rod (GR) electrodes were electrochemically modified by dendritic gold nanostructures (DGNs) followed by immobilization of glucose oxidase (GOx) in the presence of mediator phenazine methosulfate (PMS). Modified with polyaniline (PANI) or polypyrrole (Ppy), GOx/DGNs/GR electrodes were used in glucose biosensor design. Different electrochemical methods were applied for the registration of glucose concentration, and constant potential amperometry (CPA) was chosen as the best one. PANI and Ppy layers synthesized enzymatically on the GOx/DGNs/GR electrodes extended the linear glucose determination range, the width of which depended on the duration of PANI- and Ppy-layers formation. Enzymatically formed polypyrrole was determined as the most suitable polymer for the modification and formation of the glucose biosensor instead of polyaniline, because it was 1.35 times more sensitive and had a 2.57 times lower limit of detection (LOD). The developed glucose biosensor based on the Ppy/GOx/DGNs/GR electrode was characterized by appropriate sensitivity (59.4 μA mM−1 cm−2), low LOD (0.070 mmol L−1), wide linear glucose determination range (up to 19.9 mmol L−1), good repeatability (8.01%), and appropriate storage stability (33 days). The performance of the developed glucose biosensor was tested in biological samples and beverages.

Functionalization of Screen-Printed Sensors with a High Reactivity Carbonaceous Material for Ascorbic Acid Detection in Fresh-Cut Fruit with Low Vitamin C Content

In this study, carbon screen-printed sensors (C-SPEs) were functionalized with a high reactivity carbonaceous material (HRCM) to measure the ascorbic acid (AA) concentration in fresh-cut fruit (i.e., watermelon and apple) with a low content of vitamin C. HRCM and the functionalized working electrodes (WEs) were characterized by SEM and TEM. The increases in the electroactive area and in the diffusion of AA molecules towards the WE surface were evaluated by cyclic voltammetry (CV) and chronoamperometry. The performance of HRCM-SPEs were evaluated by CV and constant potential amperometry compared with the non-functionalized C-SPEs and MW-SPEs nanostructured with multi-walled carbon nanotubes. The results indicated that SPEs functionalized with 5 mg/mL of HRCM and 10 mg/mL of MWCNTs had the best performances. HRCM and MWCNTs increased the electroactive area by 1.2 and 1.4 times, respectively, whereas, after functionalization, the AA diffusion rate towards the electrode surface increased by an order of 10. The calibration slopes of HRCM and MWCNTs improved from 1.9 to 3.7 times, thus reducing the LOD of C-SPE from 0.55 to 0.15 and 0.28 μM, respectively. Finally, the functionalization of the SPEs proved to be indispensable for determining the AA concentration in the watermelon and apple samples.

Glucose Biosensor Based on Dendritic Gold Nanostructures Electrodeposited on Graphite Electrode by Different Electrochemical Methods

In this research, we have demonstrated a one-step electrochemical deposition of dendritic gold nanostructures (DGNs) on a graphite rod (GR) electrode without any template, seeds, surfactants, or stabilizers. Three electrochemical methods, namely, constant potential amperometry (CPA), pulse amperometry, and differential pulse voltammetry, were used for DGN synthesis on GR electrode and further application in enzymatic glucose biosensors. Formed gold nanostructures, including DGNs, were characterized by a field emission scanning electron microscopy. The optimal concentration of HAuCl4 (6.0 mmol L−1), duration of DGNs synthesis (400 s), electrodeposition potential (−0.4 V), and the best electrochemical method (CPA) were determined experimentally. Then the enzyme, glucose oxidase, was adsorbed on the surface of DGNs and covalently cross-linked with glutaraldehyde vapor. The enzymatic glucose biosensor based on DGNs electrodeposited at optimal conditions and modified with glucose oxidase showed a quick response (less than 3 s), a high saturation current (291 μA), appropriate linear range (up to 9.97 mmol L−1 of glucose, R2 = 0.9994), good repeatability (RSD 2.4, 2.2 and 1.5% for 2, 30, 97 mmol L−1 of glucose), low limit of detection (0.059 mmol L−1, S/N = 3) and good stability. Additionally, this biosensor could be successfully applied for glucose determination in real samples with good accuracy. These results proved the principle of enzymatic glucose biosensor development based on DGNs as the basis for further investigations.

Dispersed Conducting Polymer Nanocomposites with Glucose Oxidase and Gold Nanoparticles for the Design of Enzymatic Glucose Biosensors.

Biosensors for the determination of glucose concentration have a great significance in clinical diagnosis, and in the food and pharmaceutics industries. In this research, short-chain polyaniline (PANI) and polypyrrole (Ppy)-based nanocomposites with glucose oxidase (GOx) and 6 nm diameter AuNPs (AuNPs(6 nm)) were deposited on the graphite rod (GR) electrode followed by the immobilization of GOx. Optimal conditions for the modification of GR electrodes by conducting polymer-based nanocomposites and GOx were elaborated. The electrodes were investigated by cyclic voltammetry and constant potential amperometry in the presence of the redox mediator phenazine methosulfate (PMS). The improved enzymatic biosensors based on GR/PANI-AuNPs(6 nm)-GOx/GOx and GR/Ppy-AuNPs(6 nm)-GOx/GOx electrodes were characterized by high sensitivity (65.4 and 55.4 μA mM−1 cm−2), low limit of detection (0.070 and 0.071 mmol L−1), wide linear range (up to 16.5 mmol L−1), good repeatability (RSD 4.67 and 5.89%), and appropriate stability (half-life period (τ1/2) was 22 and 17 days, respectively). The excellent anti-interference ability to ascorbic and uric acids and successful practical application for glucose determination in serum samples was presented for GR/PANI-AuNPs(6 nm)-GOx/GOx electrode.

Platinum–Nickel Bimetallic Nanosphere–Ionic Liquid Interface for Electrochemical Oxygen and Hydrogen Sensing

By exploiting the benefits of bimetallic platinum–nickel (Pt–Ni) alloy nanosphere and an ionic liquid (IL) (i.e., 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BmpyNTf2), an organic–inorganic hybrid interface of IL/Pt–Ni was designed and characterized for electrochemical sensing of oxygen and hydrogen gases for miniaturized electrochemical gas sensor development. The spherical Pt–Ni alloy nanoparticles (NPs) were synthesized through template-free, one-pot solvothermal method. The morphology, crystal structure, and chemical composition of Pt–Ni alloy NPs were thoroughly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained Pt–Ni alloy NPs were used to fabricate the planar sensor devices and tested for oxygen and hydrogen sensing. The oxygen-sensing performance of the resulting planar electrochemical sensor was investigated over a low concentration range of 500–5000 ppm of O2 at room temperature by using constant potential amperometry. The planar electrochemical sensor device exhibited a high sensitivity to O2 ((3.04 ± 0.18) × 10–5 mA cm–2 ppm–1) compared to commercial Pt/C-based sensor ((2.57 ± 0.22) × 10–5 mA cm–2 ppm–1). The planar electrochemical sensor device also showed good reproducibility and selectivity for oxygen detection during sensing tests. Moreover, the sensor device based on the obtained Pt–Ni alloy NPs was investigated for hydrogen detection with excellent analytical performance in hydrogen sensing. The outstanding gas sensing properties were attributed to unique interface properties and highly efficient catalytic reaction of gas species of oxygen and hydrogen at the interface of IL/Pt–Ni alloy NPs. This work demonstrated that the integration of Pt–Ni alloy NPs with ILs enabled beneficial electrode interface for O2 and H2 gases sensing with high sensitivity, rapid gas response, and superior reproducibility based on a novel planar electrochemical sensor platform.

A highly sensitive and stable electrochemical nitrate biosensor

We report an electrochemical nitrate biosensor incorporating the enzyme nitrate reductase (NR) from the fungus Neurospora crassa entrapped within a polymeric chitosan matrix on a glassy carbon (GC) electrode. The artificial electron mediator anthraquinone sulfonate (AQ) is utilized as an electron transfer partner (co-substrate) for NR. The NR enzyme was effectively immobilized within the chitosan matrix without the need for a dialysis membrane, and exhibited high sensitivity and selectivity for nitrate using either rotating disk cyclic voltammetry or constant potential amperometry methods. A particular feature was the longevity of the biosensor which retained more than 70% activity over a period of 3 months. The practical application of the biosensor was demonstrated by the determination of nitrate concentrations in lake and river water samples without any pre-treatment, and the results were validated with a reliable spectroscopic assay.

Neurotransmitter Release of Reprogrammed Cells Using Electrochemical Detection Methods.

The detection of neurotransmitter release from reprogrammed human cell is an important demonstration of their functionality. Electrochemistry has the distinct advantages over alternative methods that it allows for the measuring of the analyte of interest at a high temporal resolution. This is necessary for fast events, such as neurotransmitter release and reuptake, which happen in the order of milliseconds to seconds. The precise description of these kinetic events can lead to insights into the function of cells in health and disease and allows for the exploration of events that might be missed using methods that look at absolute concentration values or methods that have a slower sampling rate. In the present chapter, we describe the use of constant potential amperometry and enzyme-coated multielectrode arrays for the detection of glutamate in vitro. These biosensors have the distinct advantage of "self-referencing," a method providing high selectivity while retaining outstanding temporal resolution. Here, we provide a step-by-step user guide for a commercially available system and its application for in vitro systems such as reprogrammed cells.

Electrochemical Evaluation of Laccase Activity in Must

As laccase (produced by Botrytis cinerea) can significantly alter the properties of wine, winemakers frequently use commercially available colorimetric kits and spectrophotometers to measure the activity of this enzyme in grapes, must and wine. Although the used kits are based on electrochemically active substrates (such as syringaldazine and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS), the electrochemical determination of laccase activity as an alternative to the colorimetric determination was not thoroughly investigated up to now. Therefore, in the present work, we explored the electrochemical determination of laccase activity. Laccase activity measurements were carried out using either carbon fiber microelectrodes or screen-printed electrodes as working electrodes, either syringaldazine or ABTS as the electrochemically active laccase substrate, and either cyclic voltammetry or constant potential amperometry as the electrochemical method. The best performing approach, which combines ABTS, screen-printed gold electrodes, and constant potential amperometry, allowed identifying laccase positive must sample (i.e., must samples with › 3U/mL laccase) in about 5 min.

Chronoamperometry as effective alternative technique for electro‐synthesis of ortho‐phenylendiamine permselective films for biosensor applications

AbstractAnalyte quantification in first generation electrochemical biosensors is threatened by electro‐active molecules, such as ascorbic acid (AA). Electrochemical deposition of ortho‐phenylendiamine (oPD) on transducer considerably reduces AA interfering. These properties of poly‐oPD (PPD) are influenced by electro‐polymerization conditions. Chronoamperometry (CA) is proposed as an alternative technique for oPD electro‐deposition over Pt. Pt/PPD sensors are evaluated through functional parameters related to AA rejection and analytical performances. N2, O2, and air bubbled supporting electrolyte and several step duration times are used. Best performing CA‐PPD sensor is obtained in N2‐purged phosphate solution containing 300 mM oPD by means of a 1 s step duration/120 steps CA. High performing PPD is achieved in shorter time compared to commonly used constant potential amperometry. Aging of polymeric features and scanning electron microscopy investigations are performed and optimized CA electro‐polymerization conditions are used to build up an efficient interference blocking layer in a glucose oxidase biosensor.

Electrochemical formation of silver nanoparticles and their applications in the reduction and detection of nitrates at neutral pH

A glassy carbon electrode modified with silver nanoparticles was employed as a nitrate sensor to give a calibration curve with a sensitivity of 2.6 μA μM−1 cm−2 and a LOD of 4.1 μM NO3− at a neutral pH. The calibration curve was generated using rotating disc voltammetry coupled with constant potential amperometry, giving efficient diffusion of the nitrate to the surface. Reasonably good selectivity for nitrate was observed in the presence of nitrite, chloride and phosphate anions. The nitrate diffusion coefficient was estimated as 1.41 × 10−5 to 1.73 × 10−5 cm2 s−1 using a combination of cyclic voltammetry and rotating disc voltammetry, while the rate constant for the nitrate reduction reaction was estimated as 0.11 cm s−1. Some deviations from the Randles–Sevick and Levich equations were seen at higher scan rates, consistent with the slow kinetics and nitrate adsorption. While stable silver nanoparticles were electrochemically formed in the solution phase and incorporated within a hydrogel matrix, the best approach in forming the nitrate sensor was the direct electrodeposition of silver nanoparticles at glassy carbon at − 0.50 V versus Ag|Ag+ following a 60-min seeding period at the open-circuit potential.

Oxygen evolution at IrO2-modified Ti anodes prepared by a simple galvanic deposition method

Highly active IrO2-modified Ti anodes have been prepared via a simple galvanic deposition process whereby a Ti substrate (freshly etched in boiling HCl containing fluoride ions) has been treated with an Ir(IV) solution, resulting in the reduction-deposition of Ir(IV) as metallic Ir on the surface of the Ti substrate with the simultaneous oxidation of nearby freshly etched Ti sites. Cyclic voltammetry of the resulting (Ir-TiO2)/Ti electrode in acidic solutions revealed features of IrO2 formation at positive applied potential values during continuous potential cycling. SEM micrographs showed good Ir dispersion on the Ti substrate, while EDS and XPS analysis of the deposits provided direct evidence for Ir and IrO2 presence on the surface of the electrodes. These electrodes, when tested as oxygen evolution reaction (OER) anodes by slow potential sweep voltammetry and constant potential amperometry, exhibited one of the highest mass specific activities for OER (560 mA mgIr−1) reported for IrO2 anode materials.

A Storage-Dependent Platinum Functionalization with a Commercial Pre-Polymer Useful for Hydrogen Peroxide and Ascorbic Acid Detection.

A preliminary assessment of properties of the commercial product Chemiplus 2DS HB (BI-QEM Specialties SpA) is proposed. Cyclic voltammetry of this oligomer containing sulfate/sulfone groups shows a single oxidative peak at +0.866 V vs. Ag/AgCl, and its passivating process on Pt electrode suggests the formation of a non-conductive layer. Electrode modification was achieved by exploiting the constant potential amperometry setting potential at +0.900 V vs. Ag/AgCl. A substantial change in the oxidative currents from electroactive species H2O2 and ascorbic acid (AA) were observed on Pt/Chemiplus 2DS HB sensors compared to unmodified Pt. Furthermore, the influence of different storage conditions on modified sensors was examined. A storage solution containing AA concentration from 0.1 until 10 mM maintained effective AA rejection of Pt/Chemiplus 2DS HB after 7 days from construction; H2O2 oxidation capability was also retained. Sulfone and sulfonate groups of Chemiplus 2DS HB are likely responsible for the dimensionality of the film and the electrostatic interaction leading to a self-blocking/self-rejection of AA. The way Pt/Chemiplus can reveal the AA presence depends on the maintaining of AA rejection, and this peculiarity can distinguish it from other sensors or biosensors.