Effective Electrode Surface Area Research Articles

Plant-based zinc nanoflowers assisted molecularly imprinted polymer for the design of an electrochemical sensor for selective determination of abrocitinib

The first electrochemical sensor application in the literature is described for the sensitive and selective determination of the selective Janus kinase (JAK)-1 inhibitor abrocitinib (ABR). ABR is approved by the U.S. Food and Drug Administration (FDA) for the treatment of atopic dermatitis. The molecularly imprinted polymer (MIP)-based sensor was designed to incorporate zinc nanoflower (ZnNFs)-graphene oxide (GO) conjugate (ZnNFs@GO), synthesized from the root methanolic extract (RME) of the species Alkanna cappadocica Boiss. et Bal. to improve the porosity and effective surface area of the glassy carbon electrode (GCE). Furthermore, the MIP structure was prepared using ABR as a template molecule, 4-aminobenzoic acid (4-ABA) as a functional monomer, and other additional components. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the surface and structure of the synthesized nanomaterial and MIP-based surface. Among the electrochemical methods, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were preferred for detailed electrochemical characterization, and differential pulse voltammetry (DPV) was preferred for all other electrochemical measurements using 5.0 mM [Fe(CN)6]3–/4– solution as the redox probe. The MIP-based sensor, which was the result of a detailed optimization phase, gave a linear response in the 1.0 × 10–13 – 1.0 × 10–12 M range in standard solution and serum sample. The obtained limit of detection (LOD) and limit of quantification (LOQ) values and recovery studies demonstrated the sensitivity, accuracy, and applicability of the sensor. Selectivity, the most important feature of the MIP-based sensor, was verified by imprinting factor calculations using ibrutinib, ruxolitinib, tofacitinib, zonisamide, and acetazolamide.Graphical

Designing advanced 0D/2D heterojunctions of N, S-co-doped carbon dots/Ti3C2Tx MXene nanosheets in electrochemical sensor applications

Ti3C2Tx MXene has demonstrated well-established sensitivity in electrochemical sensing but is susceptible to oxidation. Nitrogen-sulfur doped carbon dots (N, S-CDs) were functionalized on Ti3C2Tx MXene nanosheets via a surface modification strategy, leading to significant enhancement in the performance of Ti3C2Tx MXene. The incorporation of N, S-CDs into Ti3C2Tx MXene nanosheets effectively prevents the aggregation of Ti3C2Tx MXene flakes, resulting in improvement of the interlayer spacing to 1.578 nm and a threefold expansion of the specific surface area. Furthermore, the N, S-CDs contribute to increase the effective active surface area of the Ti3C2Tx MXene electrode, facilitating accelerated the electron transfer rates and providing additional active sites. On this basis, a galvanic sensor for dopamine (DA) detection was attained through loading N, S-CDs/Ti3C2Tx on glassy carbon electrodes. The optimized sensor achieved a linear detection range of 1 μM–1000 μM for DA, with a detection limit of 0.91 μM (S/N = 3). This work presents a promising approach for the utilization of chemically stable Ti3C2Tx MXene and MXene-based sensors, offering a new avenue for quantitative detection of DA that holds potential for application in real sample analysis.

Relationship between Bubble Generation Behavior and Hydrogen Evolution Performance at High Current Densities during Alkaline Water Electrolysis

Introduction Alkaline water electrolysis (AWE) has attracted considerable attention as a method to produce hydrogen. However, one of the problems with AWE is the increase in overpotential, which is attributed to bubbles covering the electrode surface at high current densities. Therefore, it is important to understand the bubble generation behavior to develop strategies for reducing the overpotential. In this study, we observed bubble generation behavior on Platinum (Pt) electrodes using a high-speed camera [1] and conducted electrochemical measurements to investigate the relationship between the current density/electrode potential and bubble generation behavior. Experiments Pt wires with diameters of 200 μm were used as the working electrodes. The reference and counter electrodes were a reversible hydrogen electrode (RHE) and Ni rods with a diameter of 3 mm, respectively. All measurements were conducted using a three-electrode electrochemical cell with a 2 M KOH aqueous solution as the electrolyte at 303±1K. To minimize the solution resistance, the working and reference electrodes were positioned as close as possible to each other, with a separation distance of approximately 2 mm. To ensure a uniform current-density distribution, a Ni-rod counter electrode was inserted on both sides of the cell. Observation windows were installed on the sides of the cells. Only a 3-mm parallel section of the working-electrode wire was exposed to the electrolyte to observe the electrolytic reaction, while the rest of the wire was covered with PTFE heat-shrink tube and epoxy resin. After appropriate pretreatment, cyclic voltammetry (CV) measurements were performed at a scan rate of 5 mV s-1 to obtain the polarization curves. Electrochemical impedance spectroscopy (EIS) measurements were conducted at −0.2 to −0.8 V vs. RHE with a potential amplitude of 10 mV, over a frequency range of 3×105 to 1 Hz, where 60 repeated measurements were performed for each frequency. The solution resistance was obtained from Cole–Cole plots and corrected for potential losses. The current density (i geo / A cm-2) was normalized by the geometric surface area of the cylindrically shaped working electrode. Constant current electrolysis was performed under twelve conditions of i geo = −0.05 to −1.5 A cm-2. Under each condition, the formation behavior of hydrogen bubbles was photographed using a high-speed video camera. Results and discussion Figures 1 and 2 show the polarization curves at the cathode and anode, respectively [2]. The overvoltage increased with i geo, as evidenced by the shift of the polarization curves from Tafel slope, in the range of −i geo ＜ 0.9 A cm−2 at the cathode and in the range of i geo > 0.6 A cm−2 at the anode. Figure 3 shows Cole–Cole plots obtained at i geo = −1.0 A cm−2 at the cathode and Figure 4 shows Cole–Cole plots obtained at i geo = 1.0 A cm−2 at the anode [2]. Figure 5 shows the hydrogen bubble generation behavior obtained at i geo = −1.0 A cm−2 at the cathode, and Figure 6 shows oxygen bubble generation behavior obtained at i geo = 1.0 A cm−2 at the anode [2]. The Cole–Cole plots indicate the resistance component on the low-frequency side at high current densities in addition to the charge transfer resistance. Moreover, the arc shapes of the resistance components differ between the anode and cathode, suggesting that different mechanisms are responsible for the increase in the overvoltage at high current densities. We believe that these resistances arise from reactant transfer limitations due to the hydrogen and oxygen bubble layers covering the electrode surfaces. Moreover, it was also confirmed that the charge-transfer resistance is inversely proportional to the current density, indicating that the effective electrode surface area does not change over a wide range of current densities. By comparing Figures 5 and 6, it was observed that oxygen bubbles at the anode where a larger overvoltage increase than cathode was measured had larger diameters and were less likely to detach from the electrode. Furthermore, the bubble layer formed on the electrode surface was thicker on the anode than on the cathode. Acknowledgements Part of this study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in the Advancement of Hydrogen Technologies and Utilization Project (JPNP14021), commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Selective square wave voltammetric determination of tinidazole in pharmaceutical formulations, and human urine samples using poly(bis(2,2′-bipyridine)diresorcinolateruthenium(III) chloride) modified glassy carbon electrode

This study reports the determination of Tinidazole (TDL) using a modified glassy carbon electrode, poly(bis(2,2′-bipyridine)diresorcinateruthenium(III) chloride) (poly(BBPDRRuC)/GCE) by a newly synthesized mixed ligand complex, bis-(2,2′-bipyridine)diresorcinateruthenium(III) chloride(BBPDRRuC). Electrochemical impedance spectroscopy (EIS) and cyclic voltamettry (CV) results demonstrated modification of the surface of the electrode by a conductive, and electroactive polymer film leading to an enhanced effective electrode surface area and their electrocatalytic role. Appearance of an irreversible reductive peak at much reduced potential with four folds current enhancement at poly(BBPDRRuC)/GCE showed the catalytic effect of the modifier by reduction of TDL. Square wave voltammetry current response of poly(BBPDRRuC)/GCE showed linear dependence on concentration of TDL in the range 10−8˗ 3.0 × 10−4 M with LoD and LoQ of 2.5 nM, and 8.2 nM, respectively. The TDL level in the studied tablet brands were in the range 96.6–101.1% of their labeled values. Spike recovery results in tablet, and human blood serum samples were in the range 98.3˗100.4%, and 98.85 ˗ 99.89%, respectively, and interference recovery results with <4.5% error. The developed method required a simple electrode modification step, a relatively chip, an easily available and non-toxic modifier, provides the least LoD, and reasonably wider linear dynamic range, and had excellent performance for the determination of TDL in tablet formulation and serum samples as compared with recently reported voltammetric methods.

Facile Synthesis of Platinum Nanoparticle-Embedded Reduced Graphene Oxide for the Detection of Carbendazim.

In recent years, there has been a significant interest in the advancement of electrochemical sensing platforms to detect pesticides with high sensitivity and selectivity. Current research presents a novel approach utilising platinum nanoparticles (NPs) and reduced graphene oxide deposited on a glassy carbon electrode (Pt-rGO/GCE) for direct electrochemical measurement of carbendazim (CBZ). A straightforward one-step electrodeposition process was applied to prepare the Pt-rGO sensing platform. The incorporation of conductive rGO nanosheets along with distinctive structured Pt NPs significantly enhanced the effective electrode surface area and electron transfer of CBZ. Additionally, when exposed to 50 µM CBZ, Pt-rGO/GCE exhibited a higher current response compared to the bare electrode. Further investigations were performed to analyse and optimise the experimental parameters that could influence pesticide detection. Under the optimised conditions of pH 7 and 5 min of accumulation time, the Pt-rGO/GCE sensor showed a linear concentration detection range from 0.1 µM to 50 µM, with a detection limit of 3.46 nM. The fabricated sensor was successfully employed for CBZ detection in milk and tap water with 98.88% and 98.57% recovery, respectively. The fabricated sensor showed higher sensitivity and reproducibility, thus indicating the potential of this technology in the development of reliable sensors for the detection of CBZ or similar pesticides in forthcoming applications.

A Voltammetric Sensor Based on Aluminophosphate Zeolite and a Composite of Betulinic Acid with a Chitosan Polyelectrolyte Complex for the Identification and Determination of Naproxen Enantiomers

A voltammetric sensor was developed based on a glassy carbon electrode with aluminophosphate zeolite finely dispersed on its surface, modified with a polyelectrolyte complex of chitosan with succinyl chitosan and betulinic acid, for the selective detection and determination of naproxen enantiomers. The electrochemical and analytical characteristics of the sensor were studied, and the effective electrode surface area (A = 9.8 ± 0.5 mm2) and charge transfer resistance (Ret = 649.9 ± 0.4 Ω) were calculated. In determining naproxen enantiomers, calibration characteristics are linear in the range from 2.5 × 10–5 to 1 × 10–3 M with limits of detection of 1.1 × 10–7 and 1.5 × 10–7 M and limits of quantification of 3.6 × 10–7 and 4.9 × 10–7 M for R- and S-naproxen, respectively. The sensor is more sensitive to R-naproxen (∆Ep = 60 mV, ipR/ipS = 1.40). The proposed sensor was used to recognize and determine naproxen enantiomers in human urine and plasma samples. Statistical evaluation of the results by the standard addition method showed that there was no systematic error.

Three-Dimensional Inkjet-Printed Electrochemical Sensor on Shape Memory Polymer for Aqueous Lead Detection

A simple, miniaturized, reproducible, and disposable 3D (inkjet-printed – additive manufacturing technology) gold plated electrochemical sensor (ECS) on shape memory polymer (SMP) has been reported in this article. This inkjet printed (IP) SMP based gold plated ECS is used to determine lead (II) in aqueous solution. The limit of detection of the proposed ECS is 7.6 μg/L (below USEPA approved detection limit – 15 μg/L). A detailed description of the design, fabrication, materials and reagents, optimization, reproducibility, and evaluation of the reported ECS is delineated in this article. The sensor consists of gold (Au) working electrode, Au counter electrode, and silver chloride (AgCl) reference electrode. Immersion gold plating technology is applied on IP silver (Ag) electrodes to fabricate Au working and counter electrodes. Chlorination using sodium hypochlorite solution is utilized to fabricate AgCl reference electrode. Sensor characterization, optimization, and evaluation are performed using cyclic voltammetry (CV) electrochemical analysis. The reported sensor has been utilized in case of 3 mM and 14.4 μg/L lead (II) diluted aqueous solution optimized using 0.1 M hydrochloric acid (HCl) for different aqueous samples i.e., deionized water and tap water. The electrochemical characterization i.e., electrochemical impedance spectroscopy (EIS) measurements for the reported electrode system (64.07±7.19 Ω) has also been introduced using phosphate buffer saline (PBS; pH 7.4). SMP incorporated IP ECS for lead (II) detection has been employed for the first time in this research. This technology has shown promising output in case of electrochemical sensing (lead (II) detection) due to increased effective electrode surface area (19.37 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) despite miniaturizing lateral surface area (4.19 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of the fabricated ECS.

Characterization and Application of a Synthesized Novel Poly(chlorobis(1,10-phenanthroline)resorcinolcobalt(II) chloride)-Modified Glassy Carbon Electrode for Selective Voltammetric Determination of Cefadroxil in Pharmaceutical Formulations, Human Urine, and Blood Serum Samples.

Cefadroxil belongs to the β-lactam antibiotics, mainly used for the treatment of various bacterial infections, caused by Gram-positive and Gram-negative bacteria. However, it is also encountering serious bacterial resistance, necessitating continuous monitoring of its level in pharmaceutical and biological samples. This study presents a selective, accurate, and precise square-wave voltammetric method based on a novel poly(chlorobis(1,10-phenanthroline)resorcinolcobalt(II)chloride)-modified glassy carbon electrode (poly(CP2RCoC)/GCE) for determination of cefadroxil (CDL). UV-vis spectroscopy, FT-IR spectroscopy, metal and halide estimation, CHN elemental analysis, and electrolytic conductivity measurement results confirmed the synthesis of the title complex modifier. Electrode characterization results revealed modification of the surface of the electrode by an electroactive and a conductive polymer film (poly(CP2RCoC)/GCE), leading to an improved effective electrode surface area. In contrast to the bare electrode, the appearance of an irreversible oxidative peak at a much reduced potential with a 7-fold current enhancement at poly(CP2RCoC)/GCE showed the catalytic effect of the modifier toward oxidation of CDL. The square-wave voltammetric current response of poly(CP2RCoC)/GCE showed a linear dependence on the concentration of CDL in the range of 1 × 10-7-3.0 × 10-4 M with a detection limit of 4.3 × 10-9. The CDL level in the selected two tablet brands was in the range of 97.25-100.00% of their labeled values. The spike recovery results in tablet, human blood serum, and urine samples were 98.85-101.30, 99.20-100.39, and 98.10-99.99%, respectively. Interference recovery results with a less than 4.74% error, lower LoD, and wider dynamic range than the previously reported methods validated the potential applicability of the present method with excellent accuracy and sensitivity based on the novel mixed-ligand complex-modified GCE (poly(CP2RCoC)/GCE) for determination of CDL in various real samples with a complex matrix.

Investigation and optimisation of turbidity and organic matter removal from surface water by electrocoagulation using response surface methodology

In this research, the response surface methodology (RSM) based on the central composite design (CCD) was applied to assess and optimise the electrocoagulation (EC) process used to remove turbidity and organic matter from surface water. The effects of operating factors on turbidity and organic matter removal were investigated: reaction time, electric current, effective electrode surface area and inter-electrode distance. The potassium permanganate method was used to estimate the organic matter by chemical oxygen demand (CODMn). Analysis of variance showed that the quadratic models developed to assess the responses were found to have high coefficients of determination values of 0.9747 and 0.9851 for turbidity and CODMn removal efficiencies, respectively. The experimental results revealed that 99.08% of turbidity and 85.96% of CODMn were removed at optimal conditions. The results show that the selected operating factors are significant, and RSM effectively optimises turbidity and organic matter removal from surface water by EC process.

Electrochemical determination of aripiprazole based on aluminium oxide nanoparticles modified carbon paste electrode.

The electrochemical oxidation of aripiprazole was explored at a carbon paste electrode modified with aluminium oxide nanoparticles by cyclic voltammetry and square-wave anodic adsorptive stripping voltammetry. Experimental parameters such as carbon paste composition, scan rate, buffer pH, accumulation time, and accumulation potential were optimized in order to obtain high analytical performance. The incorporation of aluminium oxide nanoparticles into the carbon paste matrix enhanced the effective surface area of the carbon paste electrode and improved the sensitivity. On the aluminium oxide nanoparticles modified carbon paste electrode, aripiprazole exhibited an irreversible anodic peak at +1.17 V in pH 1.8 BR buffer solution. Under optimum conditions, the peak current exhibited a linear dependence with aripiprazole concentration between 0.03 and 8.0 μM with a detection limit of 0.006 μM. The analytical applicability of the voltammetric method was evaluated by quantification of ARP in human serum samples and pharmaceutical formulations.

A glassy carbon electrode modified with polyaniline nanowires: An electrochemically effective surface area and an electrocatalytic activity for the oxidation of methanol under alkaline conditions

Polyaniline nanowires are directly synthesized on a glassy carbon electrode (3 mm diameter) by an electrochemical process. The polyaniline nanowires, of uniform size, a diameter of 85–95 nm, and high conductivity, distribute evenly throughout the surface of the working electrode. Electrochemical measurements are conducted in order to determine the electrochemically effective surface area of the obtained glassy carbon electrode modified with polyaniline nanowires, and an investigation of the electrocatalytic activity of polyaniline nanowires for the oxidation of methanol under alkaline conditions is carried out. The electrochemically effective surface area of the glassy carbon electrode modified with polyaniline nanowires is nearly 27 times larger than that of a glassy carbon electrode. In a cyclic voltammetry curve of the glassy carbon electrode modified with polyaniline nanowires measured in a 3.0 M CH3OH and 0.5 M KOH solution, an anodic peak corresponding to the oxidation of methanol under alkaline conditions appears at 0.17 V with a peak current of 34.4 μA.

Flow-through working electrode based on free-standing porous boron-doped diamond

Free-standing porous boron-doped diamond (fs-pBDD) was successfully fabricated and employed as a flow-through working electrode in flow injection analysis (FIA) experiments for the first time. fs-pBDD was fabricated by microwave plasma enhanced chemical vapour deposition growth of BDD on a SiO2 nanofiber template spin coated onto a silicon substrate in a multistep process, before being released by wet chemical etching of the silicon substrate. By means of cyclic voltammetry, the effective surface area of the fs-pBDD electrode was estimated to be 30.1 mm2. Fundamental performance parameters of the fs-pBDD electrode in an FIA system were determined utilising [Ru(NH3)6]3+/2+ redox probe. A detection potential of −0.3 V and the flow rate of 1.0 mL min−1 were selected as optimal and were further employed for recording concentration dependence, which was linear from 5 µmol L−1 to 750 µmol L−1. Limits of detection and quantification were assessed as 1.6 µmol L−1 and 5.3 µmol L−1, respectively. The obtained results thus proved functionality of the developed fs-pBDD as a perspective electrode material for use as an electrochemical detector for liquid-flow techniques.

In situ transformed three heteroleptic Co(II)-MOFs as potential electrocatalysts for the electrochemical oxygen evolution reaction

Three Co(II)-MOFs, catena- [(diaqua-(μ2-bqdc-κO,O)-(phen-κN,N)-cobalt (II)] (1),{[Co(pa)(4,4′-bipy)(H2O) (CH3OH)]•DMF}n (2) and [Co(ia)(bpe)0.5(H2O)]n (3), (H2bqdc = 2,2-biquinoline-4,4′-dicarboxylic acid, phen = 1,10-phenanthroline), (H2pa = pamoic acid) (H2ia = itaconic acid, bpe = 1,2-bi(4-pyridyl)ethane) have been re-synthesized and thoroughly characterized by FT-IR, PXRD, SEM, EDX, HRTEM, BET surface area and UV/Vis techniques. The objective of choosing three Co(II)-MOFs 1–3 composed of different ligands and having 1D, 2D and 3D structures, respectively, was to have deep insights into role of linked ligands and the structural morphology toward electrocatalytic performance. MOFs 1–3 have been examined as electrocatalysts for water oxidation and comparative assessments revealed their catalytic performance in the order 2 > 3 ≈ 1. MOF 2 shows the best electrocatalytic activity for OER, which could be due to the higher amount of cobalt present in MOF-2, faster electron transfer kinetics and higher effective electrode surface area. The onset potential of MOF 2 was comparable or less as compared to benchmark catalysts IrO2 and Pt/C. Overall studies strongly suggest that MOF 2 could be promising materials for replacement of commercial high-cost electrode material.

Sequential injection-square wave voltammetric sensor for phosphate detection in freshwater using silanized multi-walled carbon nanotubes and gold nanoparticles

Excessive phosphate could cause not only eutrophication of environment water, but also human diseases, such as hyperphosphatemia. Hence study of analytical technology of phosphate becomes important. This report based on silanized multi-walled carbon nanotubes (MWCNTs-SH) combined with Au nanoparticles (AuNPs) was presented for the quick and cost-effective determination of inorganic phosphate in freshwater. The MWCNTs-SH could realize approximately 2-fold increase in catalytic response current of molybdophosphate complex, in comparison with pristine MWCNTs. That could be interpreted that nanotube structures with nano-defects and conical shaped emission centers formed on the outer of wall could increase effective surface area of electrode and surface potential of electric double layer. Square wave voltammetry (SWV) was used to quantify the concentration of phosphate, and a sequential injection (SI) system was employed to realize automated solution handling and on-line monitoring in the design drawing. The sensor presented short response time of 8 s to phosphate with linear range from 0.5 to 15 mg L−1 and a detection limit of 0.3 mg L−1. Importantly, the favorable recovery rates of 106.6% ± 10.33% were achieved by detecting real water, and the data were verified by the standard spectrophotometry, showing that the work provided an efficient and promising strategy for phosphate monitoring in the environment filed.

Synthesis, characterization, and electropolymerization of a novel Cu(II) complex based on 1,10-phenanthroline for electrochemical determination of amoxicillin in pharmaceutical tablet formulations

UV–Vis and FT-IR results confirmed synthesis of a novel complex, aquachlorobis(1,10-phenanthroline)copper(II) iodidemonohydrate (ACP2CuIH), following a simple ion exchange reaction. CV and EIS results of potentiodynamically fabricated novel poly(ACP2CuIH)/GCE revealed modification of the electrode surface by a conductive, and electroactive polymer film leading to an increased effective electrode surface area. In contrast to the unmodified electrode, appearance of an irreversible oxidative peak at much reduced potential with five folds current enhancement at poly(ACP2CuIH)/GCE showed catalytic effect of the modifier towards oxidation of amoxicillin (AMX). DPV current response of poly(ACP2CuIH)/GCE showed linear dependence on concentration of AMX in the range 5 × 10−7 - 1.0 × 10−4 M with LOD and LOQ of 1.3 × 10−8, and 4.6 × 10−8 M, respectively. The AMX level in selected four tablet brands were in the range 95.2–101.8% of their nominal values. Spike recovery results of 98.8–100.6%, interference recovery results with less than 4.5%error, lower LOD and wider dynamic range than most of the previously reported methods validated the potential applicability of the present method based on the novel poly(ACP2CuIH)/GCE for determination of AMX in real samples with complex matrix.

(Invited) Glucose/Oxygen Wearable Biofuel Cells Based on Poly(glycidyl methacrylate)-Grafted MgO-Templated Porous Carbon

There are a lot of recent researches on high power enzymatic glucose/O2 biofuel cells (BFCs). We have reported that the use of MgO-templated porous carbon (MgOC) at the electrodes of biofuel cells dramatically improves the output power [1-4]. Using MgOC can improve the effective electrode surface area, leading to increased current density and output density. Supporting enzymes on these types of porous materials is expected to lead to increased output density. In the past researches [1-4], the enzymes physically adsorbed inside the porous carbon gradually leach from the carbon surface after long-term operation or during the replacement of the fuel solution.In this study, to prevent enzyme leakage, the enzyme or mediator were immobilized on the MgOC surface via multipoint covalent bonding; the grafting of polymers bearing pendant glycidyl groups was achieved by the polymerization of glycidyl methacrylate (GMA), initiated by electron beam irradiation on the carbon surface. Poly(glycidyl methacrylate) (poly(GMA)) bearing pendant glycidyl groups, grafted on the surface of MgO-templated carbon, is useful for forming strong multipoint covalent bonds with amino functional groups on the surface of flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH), Azure A and aminoferrocene.For example, the immobilized FAD-GDH can generate glucose-oxidation catalytic current using 1,2-naphthoquinone (12NQ) as the redox mediator, which is also captured on the electrode surface. The catalytic current is more stable than that obtained using the FAD-GDH-MgOC electrode without poly(GMA) because the leaching of FAD-GDH and 12NQ is suppressed by the enzyme capping effect.The BFC performance using the anode measured in 1.0 M phosphate buffer (PBS) containing 100 mM glucose exhibited the open circuit voltage of 0.8 V, maximum power density of 1.4 mW/cm2, and maximum current density of 4.25 mA/cm2.In the present paper, we totally discuss three types glucose/oxygen biofuel cells based on the poly(glycidyl methacrylate)-grafted MgO-templated porous carbon.

Effects of alkali ion on boosting WO3 photoelectrochemical performance by electrochemical doping

Electrochemical doping is a promising method to modify the photoelectrochemical performance of semiconductors. The published works using H ions as compensated cations have shown increased photocurrents, but theories vary about the causes of the improvement of photoelectrochemical performance. In this paper, we present the effects of cation ion and the key factors of enhancement using alkali sulfates ((Li/Na/K)2SO4) as the electrolyte for electrochemical doping. The effective electrode surface area (ECSA) was increased for the WO3 film after electrochemical doping. The Li-ion, with the smallest radius and thereby the highest potential to insert into the WO3 cell, results in the Li ion inserted WO3 with the highest photocurrent in the three electrochemically doped samples. To investigate the possible factors affecting the photoelectrochemical performance, the electrochemically doped samples and a control sample were annealed under inert gas (Ar). The lower photocurrents were observed for the electrochemically doped samples after annealing, confirming that the key factors are the increase of the effective electrode surface area caused by electrochemical doping and ion compensation, rather than the ions themselves and the chemical bonds between alkali ions and W or O.

Plastics world market update: Polypropylene (PP)

The modification of gold (Au) electrode using zirconium dioxide nanoparticles (ZrO2 NPs) has been investigated for enhanced electrochemical (EC) detection in flow-based analytical systems. The average size of ZrO2 NPs deposited in a facile procedure on the Au electrode surface was calculated as 22.5 ± 7 nm. Redox behaviour of a test solute, ferrocyanide [Fe(CN)6]4-, on the bare- and ZrO2-Au electrodes was initially investigated using cyclic voltammetry. From the voltammograms of bare- and ZrO2-Au electrodes, the EC reversibility values and effective surface area were experimentally determined for the first-time in this study. Further, EC reversibility and 100% increase in effective electrode surface area were confirmed in ZrO2-Au electrode through investigating the detection response (current). The EC performance of the ZrO2-Au electrode was then investigated in amperometric detection of selected electroactive solutes separated by reversed-phase HPLC. The limits of detection (LODs), based upon an injection volume of 10 μL for ascorbic acid, 2,3-dihydroxybenzoic acid and pyrocatechol were 0.09 μM, 0.04 μM, and 0.10 μM, respectively (RSD 2.5%, n = 9, r2 = 0.99 for concentration range 1–100 μM). These LODs for the ZrO2-Au electrode were 2-times lower for 2,3-DHBA, and pyrocatechol than the lowest LODs reported in the literature for EC detection in HPLC. The ZrO2-Au electrode demonstrated satisfactory repeatability of preparation, detection reproducibility and high stability (8.5 h) during continuous-flow in FIA and 45 days during intermittent use with HPLC, at flow rate of 0.6 mL min−1. This work has demonstrated a comprehensive EC characterisation of Au electrode with nanoparticulate ZrO2 for flow-based analytical systems.

Facile Fabrication and High Supercapacitive Performance of Three-Dimensional Mn/MnOx Periodic Arrays Architecture

In this paper, 3D-Mn/MnOx periodic arrays architecture is fabricated through a facile and efficient method. A femtosecond laser is used to generate a 3D conductive network on a metallic manganese surface which also serves as the current collector (3D-Mn), followed by chemical oxidation to form Mn2O3 and MnO2 on the surface of the 3D-Mn. Detailed electrochemical characterization reveals that the 3D-Mn/MnOx electrode exhibits good rate performance and cycle life, and the assembled 3D-Mn/MnOx supercapacitor can deliver the highest energy density of 5.6 μWh/cm2 at a power density of 21.8 μW/cm2. The enhanced performance is attributed to the unique periodic 3D-Mn/MnOx architecture which largely increases the effective electrode surface area, shortens the electron/ion transportation distance, facilitates electrolyte permeation, and reduces the contact resistance between 3D-Mn and MnOx. Importantly, MnOx is formed directly on the 3D-Mn surface, which helps to maintain the structural integrity and mechanical adhe...

Electrochemical characterisation of nanoparticulate zirconium dioxide-on-gold electrode for electrochemical detection in flow-based analytical systems

The modification of gold (Au) electrode using zirconium dioxide nanoparticles (ZrO2 NPs) has been investigated for enhanced electrochemical (EC) detection in flow-based analytical systems. The average size of ZrO2 NPs deposited in a facile procedure on the Au electrode surface was calculated as 22.5 ± 7 nm. Redox behaviour of a test solute, ferrocyanide [Fe(CN)6]4-, on the bare- and ZrO2-Au electrodes was initially investigated using cyclic voltammetry. From the voltammograms of bare- and ZrO2-Au electrodes, the EC reversibility values and effective surface area were experimentally determined for the first-time in this study. Further, EC reversibility and 100% increase in effective electrode surface area were confirmed in ZrO2-Au electrode through investigating the detection response (current). The EC performance of the ZrO2-Au electrode was then investigated in amperometric detection of selected electroactive solutes separated by reversed-phase HPLC. The limits of detection (LODs), based upon an injection volume of 10 μL for ascorbic acid, 2,3-dihydroxybenzoic acid and pyrocatechol were 0.09 μM, 0.04 μM, and 0.10 μM, respectively (RSD 2.5%, n = 9, r2 = 0.99 for concentration range 1–100 μM). These LODs for the ZrO2-Au electrode were 2-times lower for 2,3-DHBA, and pyrocatechol than the lowest LODs reported in the literature for EC detection in HPLC. The ZrO2-Au electrode demonstrated satisfactory repeatability of preparation, detection reproducibility and high stability (8.5 h) during continuous-flow in FIA and 45 days during intermittent use with HPLC, at flow rate of 0.6 mL min−1. This work has demonstrated a comprehensive EC characterisation of Au electrode with nanoparticulate ZrO2 for flow-based analytical systems.