Significant Electrochemical Activity Research Articles

Simple detection of gluten in commercial gluten-containing samples with a novel nanoflower electrosensor made of molybdenum disulfide with comparison of the ELISA method.

In this study, a new electrochemical sensor based on molybdenum disulfide (MoS2) nanoflowers/glassy carbon electrode (GCE was created for the sensitive detection of gluten. The prepared nanocatalysts were characterized using scanning electron microscopy with energy dispersive spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. The effects of the prepared nanocatalysts, pH value, and dropping amounts on the results were examined in detail. The electrochemical performance of the developed sensor (MoS2 nanoflowers/GCE) was then evaluated using differential pulse voltammetry, and the sensor was found to have significant electrochemical activity against gluten. A substantial linear connection was observed in the range of 0.5-100ppm of gluten concentration under optimum experimental circumstances, and the detection limit between peak current and gluten concentration was determined as 1.16ppm. The findings showed that the MoS2 nanoflowers/GCE gluten sensor has exceptional selectivity and stability. Finally, the generated electrochemical sensor was effectively utilized for gluten detection in commercial gluten-containing materials with a detection limit of 0.1652ppm. Thus, the developed MoS2 nanoflowers/GCE sensor offers a potential method for the detection of other molecules and is a promising candidate for gluten detection in commercial samples.

Anchoring bimetallic PtAu nanoparticles on hierarchical zeolite as efficient electrocatalyst for the enhancement of ethanol electrooxidation

Zeolite materials as nanoreactor are promising candidates as catalysts for the oxidation of alcohol fuels. In the present work, the hierarchical zeolite was prepared via a hydrothermal technique. Then, the bimetallic Pt-Au-zeolite composite as electrocatalysts were synthesized by co-precipitation route. The surface morphology, composition and structure of the resulting composite were investigated by FE-SEM, EDS, XRD, XPS, BET&BJH and FT-IR. The catalytic performance of the composite has been examined in ethanol electrooxidation reactions under alkaline media. Pt-Au-zeolite exhibits superior selectivity for the electrooxidation of the ethanol, outperforming both conventional Au and Pt nanoparticles supported on zeolite crystals catalyst. The peak electrooxidation current of ethanol with Pt-Au-zeolite catalyst is 3.63 times that of Pt-zeolite with a scan rate of 50 mVs−1, which is due to the synergistic effect of Au and Pt in zeolite framework. It could be attributed to the incorporation of Au and Pt into zeolite framework, which was beneficial to the charge transferring the surface of Pt-Au-zeolite electrocatalyst and facilitated the ethanol oxidation. Besides, the significant electrochemical activity can be due to the production of OH–, which leads to the species present on the surface of the electrocatalysts during the activation process that controlled by the zeolite framework.

High electrochemical active Au-NP/2D zinc-metal organic frameworks heterostructure-based ECL sensor for the miRNA-522 detection in triple negative breast cancer

In this work, a novel electrochemiluminescence (ECL) sensor has been developed to detect the miRNA-522 in the tumor tissues of triple-negative breast cancer (TNBC) patients. Au NPs/Zn MOF heterostructure was obtained by in situ growth and used as novel luminescence probe. Firstly, zinc-metal organic framework nanosheets (Zn MOF NSs) were synthesized with Zn2+ as the central metal ion and 2-aminoterephthalic acid (NH2-BDC) as the ligand. 2D MOF nanosheets with ultra-thin layered structure and relatively large specific surface areas can enhance the catalytic activity in the ECL generation. Furthermore, the electron transfer capacity and the electrochemical active surface area of MOF were greatly improved by the growth of Au NPs. Therefore, Au NPs/Zn MOF heterostructure showed the significant electrochemical activity in the sensing process. In addition, the magnetic Fe3O4@SiO2@Au microspheres were used as capture units in the magnetic separation step. The magnetic spheres with hairpin aptamer H1 can capture target gene. Then the captured miRNA-522 triggered the target catalyzed hairpin assembly (CHA) sensing process and linked Au NPs/Zn MOF heterostructure. The concentration of miRNA-522 can be quantified by the ECL signal enhancement of the Au NPs/Zn MOF heterostructure. Due to the high catalytic activity of Au NPs/Zn MOF heterostructure and their unique structural and electrochemical properties, the prepared ECL sensor achieved high-sensitive detection of miRNA-522 in the range of 1 fM to 0.1 nM with the detection limit of 0.3 fM. This strategy can provide a potential alternative for miRNA detection in medical research and clinical diagnosis of triple negative breast cancer.

Characterization of Sr2Fe1,5Mo0,5O6-δ Based Solid Oxide Electrolysis Cells

Solid oxide electrolysis cells were made with (La0,6Sr0,4)0,99Co0,96Ti0,04O3-δ (LSCT) and (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) air electrode materials and Sr2Fe1.5Mo0.5O6-δ (SFM) and SFM/ Ce1-xGdxO2−δ (GDC) fuel electrodes. LSCF has shown significantly higher electrochemical activity when compared to LSCT electrode while at the same time LSCT has proven to be more stable. SFM/GDC fuel electrode demonstrates significant electrochemical activity in electrolysis mode when compared to pure SFM electrode. Additionally, modified method to synthesize electrode powders with different particle size distributions via spray pyrolysis method was developed.

Novel Metal-Free Composite Electrodes with Carbon Quantum Dots and Anion-Conducting Ionomers for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is one of the bottlenecks in many electrochemical applications and plays an important role in commercial fuel cell systems. Platinum is highly used as a catalyzer especially in proton exchange membrane fuel cells. Given its rarity and cost, platinum, is not a viable choice as a catalyst, so there is a need to shift to alternative materials such as a metal-free catalyst possible in anion exchange membrane fuel cells. There were several theoretical and experimental studies to address this issue and a direction toward metal-free catalysts is of great interest. In this study, we focus on the oxygen reduction reaction in alkaline medium using a novel metal-free catalyst composite with carbon quantum dots and anion exchange ionomer (AEI). Doped carbon quantum dots were synthesized by a hydrothermal method and an AEI was integrated to improve the hydroxide ion transport and have a composite of desired functionality. These composites showed significant electrochemical activity with a good current response and four-electron ORR. The characterization comprised various microscopic, spectroscopic and electrochemical techniques. Figure 1

Clay Based Ionophore in PVC Membrane for their Application in Ion-Selective Electrodes

ISEs possess several advantages, such as high speed, ease of preparation, simple instrumentation, fast response time, wide concentration range, good selectivity and economically affordable. ISE based electrochemical sensors are useful in analysis of food products, drinking water, beverages, fertilizers, soil industrial effluents etc. Generally sensors are based on electroactive materials and provide a rapid and convenient means for quantitative estimation of anions and cations in biological and industrial samples. The aim of present work is to synthesize modified clay with heteropoly acids. These modified clays may have significant electrochemical activity in Ion selective electrodes. These clays can be employed as ionophore to develop chemical sensors for their application as sensors and in potentiometric titrations as indicator electrode.

Determination of the effect of exposure conducted in KOH solutions at different temperatures on the properties of electrochromic Ni(OH)2-PVA films

To determine the effect of exposure of film composite electrodes based on Ni(OH)2-polyvinyl alcohol to an alkaline solution at high temperatures on the electrochromic and electrochemical characteristics, a series of films was obtained. The films were obtained on a glass substrate coated with fluorine-doped tin oxide. The coating of the substrates was carried out by the cathodic template method under the same conditions. The resulting precipitates were treated by keeping them in an alkali solution at different temperatures: 30, 40, 50, 60, and 70 °C for 8 hours, thereby simulating the operating conditions of an electrochromic device in a hot climate. It was found that the exposure temperature directly affected the electrochemical and electrochromic properties of the treated films. In this case, the cyclic volt-ampere curves showed a decrease in the peak values of the current densities and a lower rate of establishment of characteristics with an increase in the treatment temperature. At a maximum treatment temperature of 70 °C, the properties of the film significantly changed towards deterioration. According to the results of the experiments, three temperature ranges of treatment were identified. The first one was in the range up to 40 °C, in which the films showed significant electrochromic and electrochemical activity after treatment. The second interval was between 40 and 60 °C, in which the coatings showed a reversible deterioration in electrochromic and electrochemical activity. After treatment in the second interval, the films gradually restored their performance during electrochemical cycling. The third interval was from 70 °C and above. The films treated in this temperature range irreversibly lost their electrochemical and electrochromic activity. The study also proposed mechanisms to explain changes in the characteristics of electrodes during treatment, as well as possible ways to combat temperature degradation.

Controllable nitrogen-doped carbon layers coated on NiCoO2 as electrodes for high-performance hybrid supercapacitors

Controllable nitrogen-doped carbon layers coated on NiCoO2 (NiCoO2@N-C) as anode materials are successfully synthesised by facile hydrothermal method and post-annealing treatment. Benefiting from the synergistic merits of carbon and nitrogen, the as-synthesised NiCoO2@N-C delivered an excellent capacitance of 1000 F g−1 at 1 A g−1 and a high specific capacitance of 491 F g−1 at 50 A g−1. After 5000 cycles at 10 A g−1, the cyclic stability remains 91% of the initial capacitance. Moreover, the assembled asymmetric supercapacitor exhibits a high energy density of 45.9 Wh kg−1 at a power density of 375 W kg−1. The NiCoO2@N-C hybrid nanostructure was investigated by using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques. In situ X-ray absorption near edge structure (XANES) spectroscopy was used to track the changes of NiCoO2@N-C electrode under electrochemical working conditions and confirmed that Ni had more significant electrochemical activity than Co. These findings provide new insights into the role of heteroatom doping for high-performance supercapacitors in future applications.

Study on electrochemical behavior and in vitro anticancer effect of Co(II) and Zn(II) complexes containing pyridine-2,6-dicarboxylate

Two new Cobalt(II) (C1) and Zinc(II) (C2) complexes were synthesized using the one-pot reaction of their metal salts with pyridine-2,6-dicarboxylic and also, amines containing 4-aminopyridine and/or 2-aminobenzimidazole, respectively. The structure of both compounds was determined by spectroscopic methods and single-crystal X-ray diffraction. The disordered octahedral geometry was proposed for both complexes. Cyclic voltammetry measurements on the compounds showed that C1 is a redox-active compound while significant electrochemical activity did not exhibit for C2, versus Ag/AgCl under argon. The anti-proliferative effect of the compounds was studied in vitro using oxaliplatin as a standard against three cancer cell lines including a human breast cancer (MCF7), a human colon adenocarcinoma (HT29), a human lymphocyte (HL60), as well as one normal cell line human foreskin fibroblast (HFF). The remarkable inhibition effect was indicated toward MCF7 cells by C1. Therefore, the collapse of mitochondrial membrane potential (MMP) and also the generation of reactive oxygen species (ROS) were evaluated in these cells following treatment by C1. The cytostatic effect of this complex in the MCF7 3D spheroid model was depicted.

Local Substrate Heterogeneity Influences Electrochemical Activity of TEM Grid-Supported Battery Particles.

Understanding how particle size and morphology influence ion insertion dynamics is critical for a wide range of electrochemical applications including energy storage and electrochromic smart windows. One strategy to reveal such structure–property relationships is to perform ex situ transmission electron microscopy (TEM) of nanoparticles that have been cycled on TEM grid electrodes. One drawback of this approach is that images of some particles are correlated with the electrochemical response of the entire TEM grid electrode. The lack of one-to-one electrochemical-to-structural information complicates interpretation of genuine structure/property relationships. Developing high-throughput ex situ single particle-level analytical techniques that effectively link electrochemical behavior with structural properties could accelerate the discovery of critical structure-property relationships. Here, using Li-ion insertion in WO3 nanorods as a model system, we demonstrate a correlated optically-detected electrochemistry and TEM technique that measures electrochemical behavior of via many particles simultaneously without having to make electrical contacts to single particles on the TEM grid. This correlated optical-TEM approach can link particle structure with electrochemical behavior at the single particle-level. Our measurements revealed significant electrochemical activity heterogeneity among particles. Single particle activity correlated with distinct local mechanical or electrical properties of the amorphous carbon film of the TEM grid, leading to active and inactive particles. The results are significant for correlated electrochemical/TEM imaging studies that aim to reveal structure-property relationships using single particle-level imaging and ensemble-level electrochemistry.

Two-step in-situ hydrothermal synthesis of nanosheet-constructed porous MnMoS4 arrays on 3D Ni foam as a binder-free electrode in high-performance supercapacitors

The structural engineering of electrode material for improving their electrochemical performance plays an essential role in better development in energy storage technology. In the present study, nanosheet-constructed porous MnMoS4 arrays were in-situ grown on 3D nickel foam substrate to investigate its electrochemical behavior in supercapacitors. Nickel foam, due to its favorable electrical conductivity, low weight, three-dimensional structure and high surface area was selected as the substrate in this study. MnMoS4 nanosheets (NSs) were synthesized in two in-situ hydrothermal steps. In the first step, the MnMoO4 and in the second step the MnMoS4 were synthesized using an oxide precursor. The physicochemical characteristics of MnMoS4 NSs were investigated by various techniques such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray energy diffraction (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT–IR) and Raman spectroscopy. Particularly, the obtained MnMoS4 nanosheet arrays on the nickel foam electrode illustrate significant electrochemical activity owing to their desirable structural and compositional attributes. The as-prepared electrode delivers a maximum gravimetric specific capacitance of 1865.2 F g–1 at the current density of 1 A g–1 with elevating cycling stability of 89.22 % capacitance retention after 3000 cycles. Interestingly, the asymmetric supercapacitor (ASC) assembled with the MnMoS4 nanosheet arrays and activated carbon (AC) electrodes exhibit an energy density of 58.03 Wh kg−1 at a power density of 770 W kg−1. The results show that the manganese molybdenum sulfide is a hopeful electrode material for the feasible application.

Nickel foam as a new material for chlortetracycline electrochemical oxidation: Biodegradability improvement and biological treatment

Chlortetracycline CTC is an organochlorine compound released from industrial pharmaceutical waste. This pollutant had dangerous effects in aquatic organisms and human health, since it is responsible for inhibition of microbial activity and growth. In this study, the elimination of CTC from water is targeted. Biodegradability, based on the BOD5/COD ratio was studied, showing the non-feasibility of a direct biological treatment. Cyclic voltammetry analysis on a nickel electrode revealed a significant electrochemical activity of CTC. An electrochemical pre-treatment was therefore carried out in a percolation cell using a nickel foam as a working electrode at the potential of 0.5 V/SCE. The operating parameters were optimized. A degradation yield of 99% was achieved for an initial concentration of pollutant of 50 mg L−1 and a flow rate of 5 mL min−1 in alkaline conditions. After electrolysis, a total dechlorination of CTC was observed. The biodegradability ratio was improved, from 0.13 to 0.33 after electrolysis; while the dissolved organic carbon (DOC) analysis revealed that the level of mineralization remained low 27%. A 21 days biological treatment with activated sludge was then carried out, leading to an overall mineralization yield of 78%.

Multicomponent zirconium-based metal-organic frameworks for impedimetric aptasensing of living cancer cells

We have synthesized a series of zirconium-based metal-organic frameworks (Zr-MOFs) using 1,4-dicarbxybenzene (DB), 2-aminoterephthalic acid (AA), and the mixture of AA and 2,5-diaminoterephthalic acid (DA) as ligands (represented by UiO-66, UiO-66-NH2, and UiO-66-2NH2, respectively) and developed them as platforms to anchor phosphate group-modified aptamer (PO4-Apt) and sensitively detect living Michigan cancer foundation-7 (MCF-7) cancer cells. The diversity, complexity, and amino-functionality of UiO-66-2NH2 were increased, but retained the nature of the pristine UiO-66. Compared with UiO-66 and UiO-66-NH2, the multicomponent UiO-66-2NH2 exhibited significant electrochemical activity and stronger bio-affinity toward PO4-Apt via the π−π∗ stacking, electrostatic interaction, and covalently bonds of Zr-O-P. These merits of UiO-66-2NH2 endowed the corresponding aptasensor with high ability to stabilize the formed aptamer-cells complex in aqueous solution. Meanwhile, compared with the label-free immobilized aptamer, PO4-Apt can form strong covalent bond with Zr-atom centers, thus promoting aptamer immobilization and boosting the sensing performance. The developed UiO-66-2NH2-based aptasensor displayed highly significant biosensing to detect MCF-7 cells and showed extremely low detection limit of 31 cell mL−1 in a wide linear range from 100 to 100,000 cell mL−1, as well as high specificity, good stability, and outstanding reproducibility. The present work studied the modulated sensing ability of the multicomponent MOFs for living cancer cells and provided alternative approach for the early diagnosis of cancer.

Fabrication and electrochemical properties of well-dispersed molybdenum oxide nanoparticles into nitrogen-doped ordered mesoporous carbons for supercapacitors

Environment-friendly supercapacitors demand the high-performance electrode materials working with neutral aqueous electrolyte. In this work, the nitrogen-doped ordered mesoporous carbons (NOMCs) have been synthesized and subsequently modified with molybdenum oxide nanoparticles (NPs) by a self-developed temperature controlled impregnation method. The prepared hybrids possess ordered mesoporous structure, high specific surface area (600–1000 m2 g−1), favorable pore size (∼4 nm) and well-dispersed uniform molybdenum oxide NPs. The results demonstrate that the nano-sized molybdenum oxides encapsulated in the ordered mesoporous channels exhibit significant electrochemical activity with an enhanced specific capacitance up to 410 F g−1, which can be attributed to the nanosize effects from the nanopore confinement and efficient surface area of molybdenum oxide NPs under well dispersion. The hybrids exhibit quasi-rectangular CV curves within the enlarged potential window compared with the pristine NOMCs together with pairs of redox peaks owing to the multi-valance changes of molybdenum corresponding to the Faradaic reactions. Thus, the synthesized hybrids demonstrate not only the synergistic contribution of electrical double-layer capacitance and pseudocapacitance but also superior cycling stability in aqueous neutral electrolyte.

Multiplex compounds of Ni, Cu, Co-based oxyphosphide nanowire arrays grown on Ni foam: A well-designed free-standing anode for high-capacity lithium storage

Mixed-metal oxides/phosphides with significant electrochemical activity have been considered as one of the most promising electrode materials alternatives for high-performance lithium storage. Based on this consideration, multiplex compounds of Ni, Cu, Co-based mixed-metal oxyphosphide nanowires arrays supported on nickel foams have been designed and fabricated successfully via an improved surfactant-assisted route, in which a facile hydrothermal reaction produced homogenously mixed Ni, Cu, Co-precursors and the following controllable oxidation and phosphidation were used to produce the oxyphosphide products. Different from traditional binary transition metal oxides or phosphides, three different kinds of metal cations and binary anions of O and P were introduced here and resulted in an enhanced synergistic effect to promote more efficient electrochemical reaction activity with Li+. Benefiting from the rational design of multiplex composition and the excellent 3D integrated structures assembled with 1D mesoporous nanowires, the obtained Ni, Cu, Co-based oxyphosphides exhibited remarkable lithium storage performance with high reversible capacities of 1354.6 mA h g−1 after 200 cycles at the current density of 500 mA g−1 and excellent rate capability.

Facile synthesis of nickel-cobalt selenide nanoparticles as battery-type electrode for all-solid-state asymmetric supercapacitors

Transition metal selenides attract extensive attentions in the aspect of electrochemical energy storage due to the good conductivity and significant electrochemical activity. Herein, we develop a facile mothed to synthesize nickel cobalt selenides nanoparticles by hydrothermal approach. Benefiting from the synergistic effect between Co and Ni, the optimized Ni0.6Co0.4Se2 electrode shows a specific capacity of 602.6 C g−1 at 1 A g−1 and superior rate characteristic (468.5 C g−1 at 20 A g−1). More interestingly, an all-solid-state asymmetric supercapacitor was constructed utilizing the BNPC material as the negative electrode and the Ni0.6Co0.4Se2 samples as the positive electrode shows a high energy density of 42.1 Wh kg−1 and superior cycling stability (91.0% capacity maintenance after 5000 cycles) in KOH/PVA gel electrolyte. These exciting characteristics provide a new idea for the construction of transition metal selenide electrode materials for high performance supercapacitors.

An experimental study on the corrosion sensitivity of metal alloys for usage in PCM thermal energy storages

The vast majority of renewable energy systems, especially solar ones, include thermal energy storage (TES). TES with phase change materials (PCMs) are now an established technology in several applications, but their commercialization and mass introduction cannot ignore reliability, in terms of service life of components. Among PCMs, salt hydrates are widely used but are potentially corrosive. In the present paper, the corrosion behaviour of three metal alloys (AISI 1050 carbon steel, AA 6061 aluminium and CW024A copper alloys) is investigated with magnesium nitrate hexahydrate molten salt at 120 °C. Contrary to previous studies, the study is not based on visual observation or mass loss, but corrosion sensitivity is instead studied via electrochemical impedance spectroscopy (EIS). The results highlight that good corrosion stability was observed for the aluminium alloy, since no evidence of corrosion phenomena were observed on its surface. However, carbon steel and copper alloys show significant electrochemical activity, together with a large amount of corrosion products, after just a few hours of immersion in the severe environmental conditions. Corrosion mechanisms were proposed by fitting EIS curves with several equivalent circuits, therefore suggesting design approaches for PCM-TES systems.

Thermoelectrochemical Activation of CoO in Na Cells

CoO is normally electrochemically inactive in sodium half-cells at room temperature. Here, it was found that CoO has significant electrochemical activity when cycled at 60°C (up to 550 mAh/g). In addition, CoO could be made electrochemically active at 30°C after undergoing one sodiation half-cycle at 60°C. Such in-situ thermoelectrochemical activation was found to be advantageous over ball milling. Combining ball milling with thermoelectrochemical activation, resulted in the highest reversible capacity achieved for CoO (300 mAh/g or 1800 Ah/L) and the best cycling retention.

Deciphering Combined Interactions of Algae-Bacteria Co-Culture for Green Sustainable Applications

Microalgae contained abundant value compositions (e.g., antioxidant polyphenolics and flavonoids, proteins) and owned significant bioelectrochemical characteristics for sustainable applications. This study tended to decipher strategy to maximize generation of value-added products through testing of electrochemical capabilities (e.g., total polyphenolics content, DPPH antioxidant activities, cyclic voltammetry). Although extracellular metabolites of microalgae might express significant electrochemical activity as electron shuttles, such metabolites apparently still inhibited microbial activities, leading to significant reduction of power generation in microbial fuel cells with metabolite supplementation. This result clearly explained why slow-growing microalgae could propagate ubiquitously even microbes were grown in much faster rates. That is, combined interactions of microalgae-bacteria co-cultures evidently provided ecologically favorable conditions for microalgal persistence due to inhibitory metabolites expressed by microalgae in co-cultures.

Encapsulated iron-based oxygen reduction electrocatalysts by high pressure pyrolysis

Non-precious metal catalysts (NPMCs) are candidate materials to replace platinum for proton exchange membrane fuel cells (PEMFCs). Herein we reported a type of iron-based NPMCs prepared by high pressure pyrolysis for the oxygen reduction reaction (ORR) in acidic media. The catalysts are in form of carbon microspheres in a sub-microscale consisting of iron-containing nanoparticles encapsulated by graphitic layers. By tailoring temperatures and duration of pyrolysis, the best ORR catalyst was achieved at 700 °C and 75 min, which exhibits an onset potential of 0.85 V at 0.1 mA cm−2 and a half-wave potential of 0.72 V in acid media. After 10,000 potential cycles, only 25 mV shift of half-wave potential is observed showing excellent stability. An analogue material prepared from nitrogen-free precursors shows significant electrochemical activity though it is much lower than that from the nitrogen containing precursors and can be improved by post treatment in ammonia. These results indicate the contribution to the catalysis from surface nitrogen functionalities and encapsulated metal-containing nanoparticles.