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Uric acid is the primary end product of human purine metabolism and has been regarded as a key parameter in urine and blood for monitoring physiological conditions. This paper presents a paper-based biosensor for a quantitative determination of uric acid using electrochemical detection. The working electrode of the biosensor is modified with graphene oxide (GO) and 5-amino-1,3,4-thiadiazole-2-thiol (ATT) by electropolymerizing ATT on the surface of graphene oxide. In this study, cyclic voltammetry (CV) measurements required only 200 μL of analyte solution. The experimental results showed that the oxidation peak current increased as the concentration of uric acid become higher and exhibited a linear relationship in the concentration range of 0.1–10 mM, indicating that this proposed biosensor has high sensitivity. In addition, this biosensor has good selectivity to detect uric acid because ATT has a specific binding with it. In human blood and body fluids, nitrites may be the only factor that can interfere with the detection of uric acid using this proposed biosensor. Nevertheless, uric acid can be discriminated from nitrite in the CV measurement due to different oxidation potentials. Thus, this proposed paper-based biosensor is a promising tool for detecting uric acid in biological samples.

Vanadium pentoxide (V2O5) is an excellent electrode material for electrochemical capacitor (ECCs) applications, but its lower electrical conductivity is the primary obstacle that restricts its practical applications. This obstacle can be eliminated by forming its nanohybrid (NCs) with a highly capacitive and conductive matrix such as MXene. MXene is a new two-dimensional (2D) material with good electronic conductivity and a larger specific surface area, making it a very suitable substrate for composite formation. Unfortunately, the two-dimensional MXene sheets stacked quickly, limiting their specific surface area and charge/mass transport properties. Here we used the hydrothermal approach to fabricate V2O5 nanowires (NWs) and form their nanohybrid with MXene via the ultrasound route. To assess electrochemical suitability, the fabricated samples were loaded onto a carbon cloth (CC) and used as a working electrode in the half-cell configuration. The nanohybrid (V2O5/MXene) sample showed a good specific capacity (Csp) of 768 F/g (at 1 A/g) because of its greater surface area, hybrid composition, excellent electrical conductivity, and passive nanostructure. It also showed superior cyclic, electrochemical and mechanical capability and maintained a specific capacity of 93.3%, even after completion of 6000 GCD tests. In addition, the nanohybrid sample electrode also exhibits superb rate performance and lost only 14.4% of its initial specific capacity on increasing the applied current density from 1 to 5 A/g. There is no doubt that V2O5 NWs inter-stack between MXene nanosheets to develop effective interface interaction and suppress their stacking.

In this work, CuO nanoparticles (NPs) decorated zinc oxide nanorods (ZnO NRs) on fluorine-doped tin oxide (FTO) substrate has been used as a working electrode. This working electrode has been used as an extended gate for field-effect transistor. The main objective is to use the EGFET (extended gate field effect transistor) as a glucose sensor. The proposed glucose sensor has good sensitivity of 6.643 mV/mM with a wide range of linearity (1mM-8mM) which covers the glucose level of human blood ranging from 4.4 mM to 6.6 mM. This novel concept of the glucose sensing using CuO NPs decorated ZnO nanorods based EGFET may be explored for sensing other saccharides such as mannose, fructose, and sucrose. This vertically grown ZnO nanorods decorated with CuO NPs based electrode gives reliable selectivity, good repeatability, and more stability. The performance of proposed sensor is also compared with commercially available glucose sensors. The sensitivity performance of the glucose sensor also confirms the capability to detect the glucose level from human blood and serum.

The electrochemical sensor fused with the principle of immunoassay can recognize the specific binding reaction of antigen and antibody, and transduce it directly into an electrical signal, realizing the rapid detection of relevant disease markers in the liquid sample. In this study, an electrochemical sensor for detecting eosinophil cationic protein (ECP), a marker of allergic rhinitis, was constructed based on a chemically modified electrode, and the surface of the carbon electrode was modified with semiconductor colloidal quantum dots (CQDs). Owing to the remarkable surface effect, size effect and unique quantum effect of CQDs, which can improve the enrichment of biomolecules and signal transduction on the surface of the carbon electrode, the lead sulfide (PbS) CQDs have good adhesion to the carbon electrode. On the basis of the ECP antibody coating and sealing treatment on the surface of the CQDs modified working electrode, combined with the differential pulse voltammetry (DPV) that can significantly reduce the background current for electrochemical performance testing, then the quantitative detection of ECP antigen of different concentrations can be achieved. The detection time of the electrochemical sensor for ECP was about 30 seconds, and the detection limit was 0.508 pg mL−1. The electrochemical sensor has the characteristics of high sensitivity, convenience and non-invasiveness, showing the potential for early screening of diseases such as allergic rhinitis.

The present study describes the development of graphene quantum dots (GQDs) based label-free immunosensor for sensing progesterone, a steroid hormone, using an electrochemical approach to monitor health issues and environmental contaminations. For this purpose, GQDs were synthesized by bottom-up approach and were deposited on glassy carbon substrate as a working electrode. The formation of GQDs was confirmed by UV–Vis, FTIR, RAMAN spectroscopy, and HR-TEM, and Cyclic Voltammetry was applied to investigate the electrochemical performance of the immunosensor. Further, the biosensor was optimized to detect progesterone at low concentrations. The proposed biosensor opens to be a promising platform for simplified and rapid steroid hormone analysis in biological applications and pharmaceutical formulations.

Herein, a fully integrated thread/textile-based electrochemical sensing device has been demonstrated. A hydrophilic conductive carbon thread, chemically modified with gold nanoparticles through an electrodeposition process, was used as a working electrode (WE). The hydrophilic thread coated with Ag/AgCl and an unmodified bare hydrophilic thread were used as reference electrode (RE) and counter electrode (CE) respectively. The device was fabricated with hydrophilic conductive carbon threads supported by capillary tubes and these integrated electrodes were placed in a 2 mL glass vial. The physico-chemical characterization of the working electrode was carried out using SEM (scanning electron microscopy) and X-ray photoelectron spectroscopy (XPS). Furthermore, the fabricated sensing platform, was tested for electrochemical sensing of arsenic. The electrocatalytic oxidation activity of arsenic in the designed platform was investigated via cyclic voltammetry (CV) and square wave Voltammetry (SWV). An oxidation peak at -0.4 V corresponding to the oxidation of arsenic was obtained. Scan rate effect was performed using CV analysis and the diffusion coefficient was found to be 2.478×10-10 with a regression coefficient of R2 = 0.9647. Further, concentration effect was accomplished in the linear range 0.4 μM to 60 μM. The limit of detection was obtained as 0.416 μM. For the practical application, effect of interference from other chemicals and real sample analysis from the tap water and blood serum sample was carried out which gave remarkable recovery values.

The rotating disk electrode technique is commonly used for screening and characterizing the performance of electrocatalysts for the oxygen reduction reaction (ORR). However, a reliable performance comparison of different electrocatalysts from different labs remains a challenge because of the inconsistency in the measurement of commercial Pt/C. Commercial Pt/C has been adopted extensively as a reference for evaluating the ORR performance of a new electrocatalyst. However, the reported ORR performances of commercial Pt/C from different labs could be significantly different because of multiple factors. Herein, we conducted a meta-analysis of the ORR performance of commercial Pt/C via data mining of the literature. This revealed the optimal testing conditions for the most repeatable ORR performance, with commercial Pt/C in both acid and alkaline electrolytes; the optimal Pt loading was 20 μg/cm2 on a 4 mm glassy carbon working electrode. The value of 0.84 ± 0.03 V was suggested as the “Golden reference” of the commercial Pt/C (with Pt 20 wt%) ORR half-wave potential for the performance evaluation of other ORR catalysts in both acid and alkaline electrolytes. The conclusion obtained through the meta-analysis was confirmed by experiments. This study provides general guidance for a reliable measurement of the ORR performance of commercial Pt/C as a reference.

In recent era of modern and bendable technology, energy dearth arises as a paramount subject around the globe with a dire demand of flexible and lightweight energy storage devices. This study targets fabrication of reduced graphene oxide (rGO) and utility of abundantly available, cost effective, and environment friendly lignocelluloses (LC) fibers extracted from Carica papaya source, as a binder to bind active material (rGO) as robust and compact paper sheet. Fabricated samples were analyzed by X-ray diffraction for crystallographic analysis, Scanning electron microscopy, Transmission electron microscope for morphology, Fourier transform infrared spectroscopy for structural bonding, and Raman spectroscopy for vibrational modes. Robust and bendable rGO/LC paper electrode was tested for energy storage application by employing in different characterizations, i.e., cyclic voltammetry for capacitive behavior, galvanostatic charge–discharge for symmetric EDLC, and electrochemical impedance spectroscopy for resistive charge kinetics, respectively. rGO/LC composite sheet employed as working electrode in 3-electrode CV measurements and revealed specific capacitance of 591 F/g at a scan rate of 5 mV/s by keeping the undistorted shape of voltammograms at higher scan rates which present it as a suitable candidate for modern flexible and energy storage devices. rGO/LC-based symmetric cell revealed the highest specific capacitance of 228 F/g at applied current density of 0.1 A/g, the energy density of 6.3 Wh/kg, and power density of 129 W/kg, respectively. rGO/LC-based symmetric cell confirmed the cycling stability by revealing capacitance retention of 82% after 200 cycles. It can conclude that biomass-based rGO paper sheet can be a potential candidate as environmentally safe with remarkable electrochemical activity in energy storage applications.

Screen-printed electrodes (SPEs) are ubiquitous within the field of electrochemistry and are commonplace within the arsenal of electrochemists. Their popularity stems from their reproducibility, versatility, and extremely low-cost production, allowing their utilization as single-shot electrodes and thus removing the need for tedious electrode pretreatments. Many SPE studies have explored changing the working electrode composition and/or size to benefit the researcher's specific applications. In this paper, we explore a critical parameter of SPEs that is often overlooked; namely, we explore changing the length of the SPE connections. We provide evidence of resistance changes through altering the connection length to the working electrode through theoretical calculations, multimeter measurements, and electrochemical impedance spectroscopy (EIS). We demonstrate that changing the physical length of SPE connections gives rise to more accurate heterogeneous electrode kinetics, which cannot be overcome simply through IR compensation. Significant improvements are observed when utilized as the basis of electrochemical sensing platforms for sodium nitrite, β-nicotinamide adenine dinucleotide (NADH), and lead (II). This work has a significant impact upon the field of SPEs and highlights the need for researchers to characterize and define their specific electrode performance. Without such fundamental characterization as the length and resistance of the SPE used, direct comparisons between two different systems for similar applications are obsolete. We therefore suggest that, when using SPEs in the future, experimentalists report the length of the working electrode connection alongside the measured resistance (multimeter or EIS) to facilitate this standardization across the field.

Widespread usage of pesticides in agricultural practice caused their residues to appear in water and food products intended for human consumption. The potential toxicity of these resources has raised awareness about pesticide tracking in the environment. Development of reliable electrochemical sensors for the on-site determination of pesticide concentrations is envisioned as an alternative to conventional chromatographic methods which are robust, expensive and require skilled work force. Modification of the working electrode surface can result in enhanced electrochemical response towards selected pesticide making such electrode convenient sensor for facile and efficient determination of pesticides in low concentrations. New generation of nanomaterials is applied in electrode modification in order to improve its sensitivity and selectivity. The present review summarizes significant advances in voltammetric detection of pesticides for the period of the past five years. The major focus of this review is set to the types of carbon and oxide based materials, metal nanoparticles, composites and other materials employed to upgrade standard electrode configurations such as glassy carbon and carbon paste electrodes, boron doped diamond electrodes, screen printed and film electrodes, metal and amalgam, and other kinds of electrodes.

Developing active and stable electrocatalysts for hydrogen evolution reaction (HER) is vital for the sustainable production of hydrogen (H2). In this report, NiS2 nanoparticles were deposited on the two-dimension (2D) MoS2 nanosheets by atomic layer deposition (ALD). The as-prepared MoS2/NiS2 composites were used as a working electrode for HER and displayed improved catalytic efficiency over the pristine MoS2 electrode. The electrochemical measurements demonstrated that the overpotential and the Tafel slope of the optimized MoS2/NiS2 composite were −114.6 mV and 45.4 mV/dec, which were very close to the benchmark Pt/C electrode. The improved HER activity of the MoS2/NiS2 composites could be due to the synergic effects between MoS2 and NiS2. This work could provide helpful guidance on how to design and construct efficient MoS2-based electrocatalysts for HER.

Potassium-ion batteries (KIBs) are competent candidates for next-generation energy-storage systems due to the source abundance, cost efficiency, and high energy density from comparable electrode potential to lithium. However, developing practical electrode materials for KIBs is still in its infancy, and the electrochemical reaction mechanisms for a specific material are far from clear. Here, MoTe2, due to the merits of sizeable ion-intercalation interlayer spacing of Van der Waals-type material, superior electron conductivity of its metal-semimetal characteristics to wildly studied MoS2, was for the first time investigated as the working electrode for potassium storage. The potassiation/depotassiation mechanisms were unravelled, combining electrochemical analysis, ex-situ scanning electron microscope (SEM), ex-situ transmission electron microscope (TEM) and in-situ X-ray diffraction. Sub-millimetre single-crystal MoTe2 displayed a high volumetric capacity of 792.4 mAh cm−3 at initial depotassiation and maintained a gravimetric specific capacity of 210 mAh g−1 at 100 mA g−1. It decayed rapidly after 25 cycles caused by the deactivation of active electrode material from the irreversible crystalline cracking and structure evolution during the electrochemical cycling. At initial potassiation, 2H-MoTe2 was irreversibly converted to 1T-MoTe2 and then further converted to potassium telluride. And at initial depotassiation over 2.5 V (vs. K/K+), a tentative K-Mo-Te compound with R-3H Cs4Mo18Te20 structure was formed and soon irreversibly converted to K2Te3 under following potassiation. Meanwhile, the stepwise reversible conversion of K2Te3-KTe-K5Te3 predominates the continuous electrochemical processes after the initial discharge/charge. Apart from the potential application for potassium-ion batteries, the conversion mechanisms amongst potassium tellurides also provide instructions for upcoming potassium-tellurium batteries.

An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr(OtBu)2 (salfan = 1,1'-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst's oxidation state and its subsequent monomer (l-lactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly(cyclohexene oxide-b-lactide-b-cyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1-1.5) and molecular weights ranging from 7 to 26 kDa.

Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm2 with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors.

OBJECTIVES: Linagliptin (Lin) is a drug used in treatment of type 2 diabetes mellitus. In this study, the electrochemical detection of Lin and its interaction with DNA was analyzed for the first time using voltammetric methods by measuring the oxidation currents of the adenine bases of DNA before and after the interaction. In addition, the electrochemical properties of the Lin were studied. MATERIALS AND METHODS: The interaction between Lin and DNA was evaluated using differential pulse voltammetry. A three-electrode system comprising of a pencil graphite electrode as the working electrode, reference electrode (Ag/AgCl), and platinum wire as the auxiliary electrode was used in the electrochemical studies. Experimental conditions, such as the concentration, pH of the supporting electrolyte, and immobilization time were optimized to obtain maximum analytical signals. RESULTS: The adenine bases of DNA were evaluated as an analytical signal obtained at approximately +1.2 V vs. Ag/AgCl. After the Lin-DNA interaction, the oxidation currents of adenine decreased as proof of interaction. No reports have been published on Lin interacting with DNA. Based on our results, a diffusion-controlled irreversible redox process involving independent oxidation was revealed for Lin. Under optimum conditions, the detection limit was 6.7 µg/mL for DNA and 21.5 µg/mL for Lin. Based on the observations, Lin has a toxic effect on DNA. CONCLUSION: We successfully demonstrated that Lin interacts with DNA, and its influence on DNA could play a vital role in the medical effect of the drug.

This study evaluated the electrochemical performance of cellulose-based multiwalled carbon nanotubes (MWCNTs) as electrode materials. MWCNTs were subsequently treated with acid, heat, N,N′-dimethylformamide and ferrocene carboxaldehyde to obtain the following samples; a-MWCNTs, t-MWCNTs, DMF-MWCNTs and Fc-MWCNTs, respectively, with the samples isolated at each step. The techniques employed to study the physicochemical properties of the MWCNT samples were transmission and scanning electron microscopes, X-ray photoelectron spectroscopy, thermal gravimetric analysis, cyclic voltammetry, electrochemical impedance spectroscopy, nitrogen sorption analysis and Raman and Fourier transform infrared spectroscopies. The electrochemical properties of the four materials were tested by combining them with Nafion and casting them onto a Pt electrode that formed the working electrode of a three-electrode cell with Ag/AgCl as a reference electrode and a Pt counter electrode. The background electrolyte was 1 M Na2SO4. The a-MWCNTS contained the highest concentration of carboxylic oxygen moieties and resulted in an enhanced specific capacitance ( $${C}_{s}$$ ) of 42 F g−1 with the smallest voltage window of 0.30 V. The DMF-MWCNTs and t-MWCNTs had the most stable cycle stabilities and enhanced kinetic response of the electrochemical current. The Fc-MWCNTS exhibited the broadest capacitive voltage window of 0.80 V against an Ag/AgCl reference electrode, the highest specific energy density of 2.70 Wh kg−1 and the second highest $${C}_{s}$$ of 30 F g−1. The treatment protocols demonstrate material tailoring strategies that enable a comparison of the effect of carboxylic acid, phenolic and lactone moieties on MWCNTs and the resulting associated specific energy density, kinetic response, diffusion path length, cycle life and operational voltage window of the electrode material in electrochemical capacitors.

As a promising hydrogen-storage material, graphene is expected to have a theoretical capacity of 7.7 wt%, which means a carbon-hydrogen atomic ratio of 1:1. However, it hasn’t been demonstrated yet by experiment, and the aim of the U.S. Department of Energy is to achieve 5.5 wt% in 2025. We designed a spatially-confined electrochemical system and found the storage capacity of hydrogen adatoms on single layer graphene (SLG) is as high as 7.3 wt%, which indicates a carbon-hydrogen atomic ratio of 1:1 by considering the sp3 defects of SLG. First, SLG was deposited on a large-area polycrystalline platinum (Pt) foil by chemical vapor deposition (CVD); then, a micropipette with reference electrode, counter electrode and electrolyte solution inside was impacted on the SLG/Pt foil (the working electrode) to construct spatially-confined electrochemical system. The SLG-uncovered Pt atoms act as the catalytic sites to convert protons (H+) to hydrogen adatoms (Had), which then spill over and are chemically adsorbed on SLG through surface diffusion during the cathodic scan. Because the electrode processes are reversible, the Had amount can be measured by the anodic stripping charge. This is the first experimental evidence for the theoretically expected hydrogen-storage capacity on graphene at ambient environment, especially by using H+ rather than hydrogen gas (H2) as hydrogen source, which is of significance for the practical utilization of hydrogen energy.

Iron tungstate (FeWO4) nanoparticles were prepared by simple solution combustion technique. The preparation method discloses the first report on the synthesis of iron tungstate nanoparticles. The large-scale synthesis of iron tungstate nanoparticles was achieved and characterized by analytical instruments. The powder XRD patterns authenticated the presence of monoclinic phase of FeWO4 with an average crystalline size of 19nm from Scherrer equation. The optical properties were deliberately assessed with vibrational spectroscopy which predicted the optical band gap of about 2.2 eV. DC and AC conductivity studies suggested that the prepared nanoparticles exhibit excellent conductivity. Furthermore, the semiconducting nature was proved with their temperature-dependent IV curves. The photoconductivity curves serve to be an evident for excellent behavior of light-induced charge carrier’s increment on the prepared iron tungstate nanoparticles. Considerate the interactions between the electrode substrate and nanostructures being an important research in determining the inherent activity of the nanostructures. Photoelectrochemical water splitting towards oxygen evolution was performed on varying the working electrode substrates (Nickel, Platinum, stainless steel, copper) in which higher photon to oxygen conversion rates were observed to be in the increasing order of Pt > SS > Ni > Cu. Herein, the prepared photo anode will revolutionize the design of tandem cells for efficient water splitting process.

The effects of current density and electrode-normal magnetic fields on the growth and detachment characteristics of a single bubble on vertical microelectrode surface have been investigated. A high-speed camera was used to capture the bubble evolution behavior and the bubble contact characteristic parameters were extracted and analyzed with OpenCV-Python program. The results reveal that an apparent bubble coalescence behavior occurs at low current densities and can be gradually inhibited with increasing current density. With the increase of current density, the bubble growth rate, departure diameter, working electrode potential and potential fluctuations increase, while the bubble growth time first increases and then decreases continuously. The upper microelectrode surface is more easily covered than the lower microelectrode surface. The whole microelectrode can be completely covered when the current density exceeds a certain limit with and without magnetic fields. The external magnetic fields can obviously promote the bubble detachment behavior within a relatively large current density range.

Dye-sensitized solar cells (DSCs) have evolved through the highest devotion of the research community as a low-cost alternative for problematic energy conversion devices. Platinum is the most expensive metal and hence practical applications of DSCs are restricted by the usage of platinum counter electrodes. In this study, a new series of low-cost composite counter electrodes based on commercially available graphite and TiO2 nanoparticles (21 nm) are investigated. The fabricated DSCs are an assembly of TiO2 and graphite counter electrode, dye-sensitized TiO2 multilayered photoelectrode, and a gel polymer electrolyte. In such cells, the dye sensitizer absorbs photons of the visible spectrum to photogenerated electron–hole pairs, while the graphite counter electrode transfers electrons to the electrolyte to regenerate the oxidized dye in the photoelectrode. The new and low-cost series of counter electrodes were prepared to assemble quasi-solid-state DSCs in order to find optimum counter electrode composition. The study confirms that the thin film prepared by graphite/TiO2 composite is suitable for low-cost DSCs. Out of the series, the highest solar cell performance is shown by the counter electrode that contained 80 wt% graphite and 20 wt% TiO2. The photon-absorbing working electrode contained photosensitized (N719) six layers of spin-coated TiO2 nanoparticles (13 and 21 nm). In DSCs, problems inherent in liquids can be overcome when gel electrolytes replace liquid electrolytes, and thus the cells exhibited a very good short-term stability. The study confirms that the thin film prepared by graphite/TiO2 composite is suitable for low-cost DSCs. Out of the series, the highest solar cell performance is shown by the counter electrode that contained 80 wt% graphite and 20 wt% TiO2. The exhibited efficiency of 3.81% is evidently a good value for platinum-free quasi-solid-state DSC that does not contain volatile solvents in the electrolyte.

Timely and rapid detection of biomarkers is extremely important for the diagnosis and treatment of diseases. However, going to the hospital to test biomarkers is the most common way. People need to spend a lot of money and time on various tests for potential disease detection. To make the detection more convenient and affordable, we propose a paper-based aptasensor platform in this work. This device is based on a cellulose paper, on which a three-electrode system and microfluidic channels are fabricated. Meanwhile, novel nanomaterials consisting of amino redox graphene/thionine/streptavidin-modified gold nanoparticles/chitosan are synthesized and modified on the working electrode of the device. Through the biotin-streptavidin system, the aptamer whose 5'end is modified with biotin can be firmly immobilized on the electrode. The detection principle is that the current generated by the nanomaterials decreases proportionally to the concentration of targets owing to the combination of the biomarker and its aptamer. 17β-Estradiol (17β-E2), as one of the widely used diagnostic biomarkers of various clinical conditions, is adopted for verifying the performance of the platform. The experimental results demonstrated that this device enables the determination of 17β-E2 in a wide linear range of concentrations of 10 pg mL-1 to 100 ng mL-1 and the limit of detection is 10 pg mL-1 (S/N = 3). Moreover, it enables the detection of targets in clinical serum samples, demonstrating its potential to be a disposable and convenient integrated platform for detecting various biomarkers.

More and more attentions have been focused on design and synthesis of novel metal-organic framework/graphene oxide (MOF/GO) composites with unique performance. Zirconium-porphyrin MOF (PCN-222) is in-situ synthesis with the existence of GO with −COOH group to artfully fabricate a PCN-222/GO composite. This composite can be employed as functional material to modify the working electrode. Thanks to excellent electrical conductivity of GO, abundant mesoporous channels and numerous Zr(IV) metal sites of PCN-222, this composite can immobilize a large amount of aptamer through strong π-π stacking interaction and high affinity between phosphate group of aptamer and Zr(IV) site of PCN-222 simultaneously. Hence, an ultra-sensitive electrochemical aptasensor based on PCN-222/GO composite can quantificationally detect trace chloramphenicol with limit of detection of 7.04 pg/mL (21.79 pmol/L) from 0.01 ng/mL to 50 ng/mL by electrochemical impedance spectroscopy even in real samples. Meanwhile, this fabricated aptasensor reveals good repeatability, outstanding selectivity and preferable long-term storage. This research provides a useful approach to construct MOF/GO composites for fabricating electrochemical aptasensors in the electrochemical detection field.

In order to optimize the working electrode for dye-sensitized solar cells (DSSCs), three kinds of stacked-film structures with the same overall thickness of 13 μ m were prepared by using spray coating system, including pure TiO2 film, TiO2-Graphene (TG) film and TiO2/TG (TTG) bilayer film. To increase light path and excite more dye molecules, the bilayer structure of TTG film is composed with TiO2 main layer and TG scattering layer, which provide pores to adsorb N719 dye molecules. The DSSCs with pure TiO2, TG, and TTG working electrodes exhibit the efficiencies of 3.07%, 2.48%, and 4.49%, respectively. From the results, the DSSCs with TG film working electrode had the lowest efficiency, because the TG film had the defects which led to higher interfacial charges than the pure TiO2. Moreover, TTG working electrode contained a TiO2 main layer and a TG scattering layer in which the graphene material could increase the electron transport and reduce the recombination, and it was also due to the stacked structure, which could improve the light utilization and enhance the light transmitting distance. In this article, the working electrode of DSSCs was successfully modified by using TTG stacked structure with an improved efficiency of 46.25% higher than that of TiO2 working electrode.

Electrochemiluminescence (ECL) of low triggering potential is strongly anticipated for ECL assays with less inherent electrochemical interference and improved long-term stability of the working electrode. Herein, effects of the thiol capping agents and the states of luminophores, i.e., the thiol-capped CuInS2@ZnS nanocrystals (CuInS2@ZnS-Thiol), on the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O were explored on the Au working electrode. The thiol capping agent of glutathione (GSH) not only enabled CuInS2@ZnS-Thiol/N2H4·H2O with the stronger oxidative-reduction ECL than other thiol capping agents but also demonstrated the largest shift for the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O upon changing the luminophores from the monodispersed state to the surface-confined state. CuInS2@ZnS-GSH/N2H4·H2O exhibited an efficient oxidative-reduction ECL around 0.78 V (vs Ag/AgCl) with CuInS2@ZnS-GSH of the monodispersed state. Upon employing CuInS2@ZnS-GSH as the ECL tag and immobilizing them onto the Au working electrode, the oxidative-reduction ECL of CuInS2@ZnS-GSH/N2H4·H2O was lowered to 0.32 V (vs Ag/AgCl), which was about 0.88 V lower than that of traditional Ru(bpy)32+/TPrA (typically ∼1.2 V, vs Ag/AgCl). The ECL of the CuInS2@ZnS-GSH/N2H4·H2O system with the luminophore of both monodispersed and surface-confined states was spectrally identical to each other, indicating that this surface-confining strategy exhibited negligible effect on the excited state for the ECL of CuInS2@ZnS-GSH. A surface-confined ECL sensor around 0.32 V was fabricated with CuInS2@ZnS-GSH as a luminophore, which could sensitively and selectively determine the K-RAS gene from 1 to 500 pM with a limit of detection at 0.5 pmol L-1 (S/N = 3).

This work focuses on an interdisciplinary issue in energy management and biosensing techniques. Aiming at enhancing the biosensing detection of dopamine at high ambient temperatures, we developed an innovative integration of phase-change microcapsules with a metal-organic framework (MOF) based on zeolitic imidazolate framework-8 to develop an intelligent electrochemical biosensing system with a thermal self-regulation function. We first fabricated a type of electroactive microcapsules containing a MOF-anchored polypyrrole/SiO2 double-layered shell and a phase-change material (PCM) core. The resultant microcapsules not only exhibit a regular spherical morphology with a layer-by-layer core-shell microstructure but also display an effective temperature-regulation capability to enhance enzymatic bioactivity under phase-change enthalpies of around 124.0 J·g-1 along with good thermal impact resistance and excellent thermal cycling stability for long-term use in thermal energy management. These electroactive microcapsules were then used to modify a working electrode together with laccase as a biocatalyst to construct a thermal self-regulatory biosensor. With a high sensitivity of 3.541 μA·L·μmol-1·cm-2 and a low detection limit of 0.0069 μmol·L-1 at 50 °C, this biosensor exhibits much better determination effectiveness toward dopamine at higher temperatures than conventional biosensors thanks to in situ thermal management derived from its PCM core in the electroactive microcapsules. This study offers a promising approach for development of intelligent thermal self-regulatory biosensors with an enhanced detection capability to identify various chemicals accurately in a wide range of applicable temperatures.

Dye-sensitized solar cell (DSSC) has a great potential to convert solar light into electricity. In this article, a prototype of DSSC had been successfully fabricated using ZnO:Al thin film and dye from red dragon fruit as a working electrode. ZnO:Al thin films were prepared by a sol-gel spin coating method with variation of post-heating temperatures. The XRD result confirms that all ZnO:Al thin films have a hexagonal structure with crystal sizes of 16 nm to 41 nm. SEM analysis showed the nanoparticles with particle size of 30 nm to 80 nm. The bandgap ranges from 3.16 eV to 3.40 eV. The EIS analysis reveals that charge transfer resistance greatly decreases with the rise of temperature. The efficiency of DSSC gradually improved with increasing the post-heating temperature. ZnO:Al with a post-heating temperature of 600°C had the highest efficiency of 0.398%.

This paper investigates a novel electrochemical enzyme-free glucose sensor based on bimetallic PtNi materials. Pt and Ni layer were sputtered on the substrate and then annealed to form bimetallic PtNi materials, which served as sensitive materials for glucose detection. The effect of annealing temperature on the performance of enzyme-free glucose sensors had been studied deeply. Using micro-electromechanical systems (MEMS) technology, a monolithic enzyme-free glucose sensor was fabricated, which integrated with working electrode (WE) and counter electrode (CE) on a chip. The electrochemical results demonstrate that the device exhibits outstanding sensitivity and selectivity for glucose detection, achieving a maximal sensitivity of 1618.15 µA mM−1 cm−2 in the range of 0–10 mM with a low detection limit of 8.76 µM. The sensor also shows its practical application for glucose detection in human blood serum. Due to its performance and fabrication process, the enzyme-free glucose sensor is therefore well suited for glucose detection and manufacture together with other integrated circuits on a single silicon wafer, which shows potentials in implantable microelectronic systems.

Purpose The corrosion of buried steel pipelines is becoming more serious because of stress corrosion, stray current corrosion and other reasons. This paper aims to study the various alternating current (AC) interference densities on the stress corrosion cracking behaviors of X80 steel samples under cathodic protection (CP) in the simulated soil electrolyte environment by using an electrochemical method. Design/methodology/approach The change of corrosion rate and surface morphology of the X80 steel samples at various AC current densities from 0 to 150 A/m2 or CP potential between −750 and −1,200 mV in the soil-simulating environment was revealed by the electrochemical methods and slow strain rate testing methods. Findings The results revealed that with the increase of interference density, the corrosion potential of the X80 steel samples shifted to the negative side, and the corrosion pitting was observed on the surface of the sample, this may cause a danger of energy leak. Moreover, the corrosion rate was found to follow a corresponding change with the stress–strain curve. Besides, with the introduction of the CP system, the corrosion rate of the X80 steel working electrode decreased at a low cathodic potential, while showed an opposite behavior at high cathodic potential. In this study, the correlation between AC stray current, cathodic potential and stress was established, which is beneficial to the protection of oil and gas pipeline. Originality/value Investigation results are of benefit to provide a new CP strategy under the interference of AC stray current corrosion and stress corrosion to reduce the corrosion rate of buried pipelines and improve the safety of pipeline transportation.

The present study introduces a novel nanocomposite based on reduced graphene oxide, nitrogen-doped graphene quantum dots, and palladium and silver nanoparticles (rGO/NGQD/AgPd) as an electrocatalyst toward nitrite oxidation reaction. Metal nanoparticles were prepared via a green one-pot photochemical reduction procedure utilizing UV light and NGQD simultaneously as a reducing and directing agent. Formation of the nanocomposite was thoroughly demonstrated by the FT-IR, XRD, Raman, XPS, FE-SEM, and TEM characterization tests. Various electrochemical tests evaluated the efficiency of the prepared sensing platform on the surface of a gold working electrode. Sensitivity and limit of detection (LOD) were calculated to be 0.854 μA.μM−1.cm−2 and 0.052 μM, respectively, from the chronoamperometry data. Finally, the proposed sensor was successfully applied for the determination of nitrite ions in river and mineral water samples as natural water sources.

The electroactive material with a porous structure, good electrical conductivity, hybrid composition, and a higher surface is considered more suitable for applications as an electrode in the energy storage device. Herein, we report the preparation of In2O3 nanoparticles via a simple chemical route and their nanocomposites with 10% (IOG-10), 30% (IOG-30), 50% (IOG-50), 70% (IOG-70), and 100% G-100 graphene nanoplatelets (GNPs) via ultra-sonication. The presence of GNPs in the nanocomposite samples was verified by powder X-ray diffraction (PXRD), Raman, and scanning electron microscopy (SEM) results. The prepared samples were loaded onto the porous 3D nickel foam (NF) substrate to manufacture the working electrode for electrochemical testing. The cyclic voltammetry (CV), as well as galvanostatic charge/discharge (GCD), results proposed the IOG-30@NF as a suitable electrode for electrochemical applications. More precisely, the IOG-30@NF electrode shows a specific capacitance of 1768 Fg-1 at 1 Ag-1, which is considerably higher than that of either G-100@NF or In2O3@NF electrodes. Besides, the IOG-30@NF electrode shows good cyclic stability of 92.2% after 4000 GCD tests completed at 12 Ag-1. When increasing the current density value from 1 to 4, the IOG-30@NF electrode maintains a specific capability of 81%, ensuring its exceptional rate capability. The higher specific capacity, higher rate-performance, and better cyclic activity of the IOG-30@NF electrode can be ascribed to its hybrid-composition, nanoarchitecture In2O3, 3D but porous nickel foam substrate, appropriate graphene content, and interaction between In2O3 nanoparticles and GNPs nanosheets.

Hydrazine is a well-known carcinogen and can cause several other adverse effects on human health such as respiratory issues, irritation of the eyes, liver and kidney problems, and dermal corrosion. An effective method is needed to detect the carcinogenic reagent like hydrazine. Tin oxide (SnO2)-modified graphitic carbon nitride (g-C3N4) decorated with well-crystallized silver (Ag) nanoparticles (denoted as Ag@SO-gCN) was fabricated by a biogenic/green approach and characterized by standard techniques. A fluorine-doped tin oxide (FTO) support/substrate was coated with Ag@SO-gCN by the doctor-blade technique, and employed as the working electrode (denoted as Ag@SO-gCN/FTO) for the electrochemical detection of carcinogenic hydrazine (Hz) as a model analyte at room temperature. The dual electrochemical techniques of linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used for the detection of hydrazine (denoted as Hz). The Ag@SO-gCN/FTO sensor shows an effective current response in the detection of Hz in solutions. The concentration of Hz was very efficiently monitored using LSV and CV under different conditions. The sensor shows a low limit of detection (LOD), high sensitivity and selectivity, and good linear range. The sensitivity and LOD of this sensor using LSV are 2.01 μA μM−1 cm−2 and 0.164 ± 0.013 μM, respectively. However, the fabricated Hz sensor using CV showed a sensitivity of 2.305 μA μM−1 cm−2 and LOD of 0.143 ± 0.011 μM. This study thus provides an innovative Ag@SnO2-g-C3N4-based electrochemical sensor as an effective device for the successful detection of hazardous chemicals.

Herein we illustrate a rational scheme to construct nanorod structured Co3O4@Fe2O3-2DC working electrode for electrochemical capacitor applications. When analyzed as a supercapacitor electrode material, Co3O4@Fe2O3-2DC at 5 A/g delivered an optimum capacity retention of 96.7%, and a high specific capacitance of 2657.1 F/g at a marginal current density of 1 A/g. Co3O4@Fe2O3-2DC unparalleled electrochemical performance can be accredited to its unique morphology consigned with a high specific surface area of 532.8 m2/g, and the effect of synergy between single-layer practically defect free graphene, and the anchored cobalt and iron metal oxides. The electrode operated within a wide potential window, almost at the limit for aqueous electrolyte system (1.23 V), which makes it merit a high over-potential caption. These results validate Co3O4@Fe2O3-2DC to be considered as a favorable electrode material, for application in next-generation excellent performance supercapacitors.

Using powders treated by sand milling as starting materials, high densified lithium lanthanum titanium oxide (LLTO) ceramics with high conductivity were prepared. A novel all-solid-state reference electrode was fabricated using the as-prepared LLTO ceramics for electrochemical measurements in marine environments that require robustness, no clogging, and resistance to high salinity and high temperatures and pressures. This reference electrode functioned without any filling solution and any porous junction between it and the analyte. The characteristics, stability, and impedance of the all-solid-state reference electrode were examined in different pH buffer aqueous solutions; its I–V curves were recorded during cyclic voltammetric experiments, which were then compared with those obtained for a classic Ag/AgCl reference electrode. The fabricated reference electrode was connected to an Ir/IrO2 working electrode to prepare an all-solid-state pH sensor for measuring the pH of simulated seawater and for capturing variations in the behavior of the reference electrode on addition of acidic or alkaline solutions. This all-solid-state potentiometric sensor can be used in association with other sensing electrodes and in harsh environments, such as at great ocean depths and in high temperature and pressure environments.

Although the efficiency of organic polymer-based retinal devices has been proved, the interpretation of the working mechanisms that grant photostimulation at the polymer/neuron interface is still a matter of debate. To contribute solving this issue, we focus here on the characterization of the interface between poly(3-hexyltiophene) films and water by the combined use of electrochemistry and mathematical modeling. Simulations well reproduce the buildup of photovoltage (zero current condition) upon illumination of the working electrode made by a polymer film deposited onto an indium tin oxide (ITO) substrate. Due to the essential unipolar transport in the photoexcited film, diffusion leads to a space charge separation that is responsible for the initial photovoltage. Later, electron transfer reactions toward oxygen in the electrolyte extract negative charge from the polymer. In spite of the simple model studied, all of these considerations shed light on the possible coupling mechanisms between the polymeric device and the living cell, supporting the hypothesis of pseudocapacitive coupling.

In this context, the electrical conductivity and surface activity of cobalt sulphide (CoS) as counter electrode CE is improved by incorporating with graphitic carbon nitride (g-C3N4) to enhance the power conversion efficiency (PCE) of quantum dot sensitized solar cells (DSSCs). Core–shell nanocomposite CoS@g-C3N4 composed of CoS core encapsulated by graphitic carbon nitride shell in different weight ratios of CoS to constant ratio of g-C3N4 was synthesised. The prepared composites were assigned as 1:1 (CoS-1), 5:1 (CoS-5), 7:1(CoS-7), 9:1(CoS-9) and 11:1(CoS-11). The different prepared CoS@g-C3N4 nanocomposites were applied as counter electrodes (CEs) in QDSSCs based on TiO2 nanorod arrays with 84.37-nm length and 5.24-nm width as working electrode, cadmium sulphide (CdS) as quantum dots and polysulfide electrolyte. The results show that CoS-7 has superior efficiency with clear improvement in cell performance up to 10.15%, short current density Jsc of 19.5 mA/cm2, open circuit voltage Voc of 0.68 mV and fill factor (FF) of 0.78. The improved performance is attributed to the formation of synergistic heterojunction between g-C3N4 and CoS which facilitates a fast electron transfer at the interface between them; also, more photoelectrons could be produced due to the formation of carbon vacancies in g-C3N4 which made g-C3N4 to hold more excitable electrons and inhibit the recombination of photogenerated carriers. Matching the valence and conduction bands of CoS to those of g-C3N4 also catalyses collecting and mobility rate of the electrons and holes and decreases the recombination rate effectively. Cyclic voltammetry, impedance spectroscopy, the equivalent circuit, analysis of capacitance-frequency spectra, charge transfer spectra and charge recombination were also studied.

In this experiment, we designed an electrochemical sensor using penicillinase (Pen X)-rhombus porous carbon (RPC) as the detection element and hematoxylin as the indicator to detect low concentrations of penicillin sodium (Pen G). A differential pulse voltammetry (DPV) method was used to detect Pen G in the concentration range of 10-8 -10-5 mg·mL-1 under optimal experimental conditions. The results showed that the peak current value and the logarithm of Pen G concentration showed a good linear relationship (R2 = 0.9915), and the LOD was 2.68 × 10-7 mg·mL-1 (S/N = 3). The actual milk samples were detected by the addition method and compared with the high-performance liquid phase method; no significant difference was found in the detection results. The working electrode prepared by cross-linking method not only extends the service life of the sensor, but also improves the sensitivity and reproducibility of the sensor. It can also be used to detect the Pen G residue in the actual milk samples repeatedly. PRACTICAL APPLICATION: In this study, an electrochemical sensor for the rapid detection of penicillin sodium in milk was prepared, which has good sensitivity and fast detection speed.

Prussian blue (PB) is a well-known electrochromic material due to its fast response and high cycle stability. We used the multi-step electrodeposition to prepare the PB films (S-PB) with different thickness. SEM image shows that as-grown film has small particles on its surface, which is beneficial for improving electrochromic properties of thicker PB film. The S-PB film with a thickness of 410 nm shows a high transmittance modulation of 82.04% at λ = 680 nm. S-PB and CeO2-TiO2-Li films were used as working electrode and counter electrode separately to prepare electrochromic devices (ECDs), both of which are inorganic anode materials. At 680 nm wavelength, the device based on double anode materials changes transmittance from 71.25 to 11.71% and the coloration efficiency is 73.5 cm2/C. Moreover, the optical modulation of ECD does not change significantly when performing 10,000 cycles.

Quantitative scanning micropipette contact method measurements are subject to the deleterious effects of reference electrode interference. The commonly used Ag/AgCl wire quasi-reference counter electrode in the miniaturized electrochemical cell of the scanning micropipette contact method was found to leak Ag⁺ into the electrolyte solution. The reduction of these Ag⁺ species at the working electrode surface generates a faradaic current, which significantly affects the low magnitude currents inherently measured in the scanning micropipette contact method. We demonstrate that, during the microscopic corrosion investigation of the AA7075-T73 alloy using the oil-immersed scanning micropipette contact method, the cathodic current was increased by the Ag⁺ reduction, resulting in positive shifts of corrosion potentials. The use of a leak-free Ag/AgCl electrode or an extended distance between the Ag/AgCl wire and micropipette tip droplet eliminated the Ag⁺ contamination, making it possible to measure accurate corrosion potentials during the oil-immersed scanning micropipette contact method measurements.

Partial absorption of the solar spectrum is one of the key limitations of dye-sensitized solar cells (DSSCs). In an attempt to address this issue, we have developed co-sensitized working electrode based dye anchored counter electrode (DACE) DSSC strategy to achieve panchromatic absorption using multiple dyes. Herein, we have synthesized a dithionopyrrole based TP–DTP dye and a porphyrin-based Y351-S dye and explored to a new type of DSSCs modified with DACE. To realize the effect of DACE electrode on the DSSC efficiency, we have fabricated five different DSSCs devices namely, S-DSSC1, S-DSSC2, S-DACE, CO-DSSC, and CO-DACE using these synthesized dyes and compared their performances systematically. In addition, the detailed impedance and stepped light-induced transient measurements of the photocurrent and voltage (SLIM-PCV) experiments are also performed to assess the charge transfer resistance and charge collection efficiency of these devices. The highest efficiency of 8.72 ± 0.15% is observed for the CO-DACE-based devices, which is higher than the traditional DSSCs made of single dye-sensitized (S-DSSC1 and S-DSSC2), and co-sensitized DSSC (CO-DSSC). It can be attributed to the enhanced incident photon to current conversion efficiency (IPCE) and short circuit current (Jsc) which clearly portray the advantage of DACE electrode in harvesting maximum incident light.

Adsorptive Stripping Voltammetric method for Nimesulide (NIM) determination was developed. As a working electrode, glassy carbon electrode (GCE) modified with carbon black and Nafion (CB-Nafion GCE) was used. All measurements were carried out in 0.1 M acetate buffer (pH 4.6). Conducted experiments allowed to optimize differential pulse voltammetry (DPV) instrumental parameters: sampling and waiting time ts = tw = 10 ms, step potential Es = 4 mV, and pulse amplitude ΔE = 50 mV. The best results were obtained for preconcentration potential and time equal to 400 mV and 20 s, respectively. Limit of detection was calculated and was equal to 0.14 µM for 20-s preconcentration time and 0.06 µM for 40-s preconcentration time. In order to prove the applicability of the developed method, concentration of nimesulide in pharmaceutical products was determined. Calculated recoveries were in the range 94–99%, which indicates that the method might be assumed as accurate. Coefficient of variation was equal to 5.0% (n = 7, NIM concentration 1 µM) Obtained results of NIM determination were in good agreement with the content declared by producers.

The presented research introduces a fabricated working electrode of cabbage flower-like Ho3+/NiO nanostructure (CFL-Ho3+/NiO NSs) as a glassy carbon electrode for the detection of flutamide, a prostate cancer drug, through a differential pulse voltammetry (DPV). A solvothermal technique was applied to produce the CFL-Ho3+/NiO NSs, which were subsequently characterized by Map, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray diffraction methods. Three various techniques of DPV, cyclic voltammetry, and chronoamperometry as well as multiple electrodes were employed to evaluate the electrochemical properties of flutamide. The reduction process of flutamide was tested by quantitative analysis at − 526 mV and pH 7.0. Diffusion coefficient of flutamide was assessed by chronoamperometry method in phosphate buffer solution (pH 7.0). Linear results were reported for the DPV in the range between 0.01 and 400.0 μM. Under optimized conditions, the range of linear responses was between 0.01 and 400.0 μM with the limit of quantification of 18.8 nM and limit of detection of 5.7 nM. The produced electrode was practically utilized to detect flutamide in flutanax tablets and real clinical urine samples, achieving successful results. The standard addition method was performed for the detection of flutamide present in urine samples using the modified electrode. The only urine treatment in this method was a simple dilution with supporting buffer.

Developing highly active catalysts for hydrogen evolution reaction is vital for large-scale and efficient production of hydrogen through water splitting. In this study, we reported scale-up TiO2/LaFeO3 composite catalysts with multiple heterojunctions synthesized via facile solid-phase reaction and investigated their hydrogen evolution reaction (HER) performance in both acidic and alkaline solutions. To be excited, under AM1.5 simulated sunlight irradiation, the working electrode decorated by TiO2/LaFeO3 presents a higher current density with 10 mV/cm2 at 0.55 V in a 0.5 M H2SO4 solution, suppressing the corresponding performance with the occasion of pure electrocatalysis. Importantly, the hydrogen evolution efficiency can reach 7.62 mmol h−1 cm−2, overwhelming approximately 5.3 times higher than that of commercial P25 (1.43 mmol h−1 cm−2) with exceptional stability via imposing simulated sunlight and a bias of 500 mV. Therefore, such excellent catalysts could serve as an alternative to reach remarkable HER performance via fossil fuels free technology, potentially making contribution toward the goal of global “carbon neutral” by 2050.

By replacing volatile and flammable organic-based electrolytes with gel electrolytes, dye-sensitized solar cells (DSSCs) may be a viable and more practical alternative to other clean energy sources. Although they present a promising alternative, gel electrolytes still have some drawbacks for practical applications, such as low ionic conductivity and infusion difficulties into the pores of the working electrode. Here, we introduce a new one-step fabrication method that uses a lyotropic liquid crystalline (LLC) gel electrolyte (LiI:I2:H2O:C12H25(OCH2CH2)10OH) and a dye (N719) to construct a DSSC that performs (7.32%) 2.2 times better compared with a traditional two-step production. Water plays a key role in the gel electrolyte, where the H2O/LiI mole ratio is around 2.57 under ambient laboratory conditions (ALCs); however, this ratio linearly increases to 4.00 and then to 5.85 at 40 and 75% humidities, respectively, without affecting the two-dimensional (2D) hexagonal structure of the mesophase. The ionic conductivity of the gel electrolyte linearly increases accordingly, by 2.2 (4.8 × 10–5 to 10.6 × 10–5) and 13.1 times (63.0 × 10–5 S/cm) from ALC to 40 and ALC to 75% humidity, respectively. Increasing water in the gel phase improves the conductivity of the LLC mesophase and the short-circuit current (Isc) of the DSSC, but negatively influences the open-circuit voltage (Voc) of the cell, equilibrium reaction between the LiI and I2, and the anchoring of the dye molecules over the titania surface.

Only about 3% of Earth’s water is freshwater out of which only 0.4% is accessible as surface water in the form of lakes, rivers and groundwater. When harmful substances (like organic matter, industrial wastes, pesticides, fertilizers) contaminate freshwater, it becomes a major problem as they may not damage one’s health immediately but can be harmful after long-term exposure. In this context, there is a need to develop sensitive and reliable sensors that are able for in situ measurements of such contaminants. Electrochemical sensors can in situ detect target analytes based on change in current due to redox reaction of an electroactive species with the specific surface at a certain potential. Nanotechnology offers the advantage for manipulating the size and morphology of specific surface at working electrode. Here in this review article, the work done in the last few years in the field of electrochemical detection of pesticides using graphene-based nanocomposites is discussed. This review paper presents summarized work about the methods and materials for developing electrochemical sensors. Sensing mechanism is discussed, and related data is also presented to provide an overview.

We report the synthesis of silver-integrated silica nanostructures using rice hulls and silver chloride through a facile thermal combustion process. The formation of mesoporous silica nanomatrix embedded with silver nanoparticles (SiO2:Ag 5 wt% and SiO2:Ag 10 wt%) was confirmed by XRD, FTIR, EDX, BET, and TEM analysis. Also, the obtained results from the above studies revealed that the concentration of silver ions significantly increases the particle size and number of silver nanoparticles formed in the silica matrix. The electrochemical performance was studied using silver-integrated silica nanostructures as a working electrode in KOH electrolyte. The maximum specific capacitance of SiO2:Ag 5 wt%- and SiO2:Ag 10 wt%-coated electrode was found to be 517 and 580 F/g at current density of 1 A/g. It was also found that SiO2:Ag 10 wt% electrode exhibit an excellent stability with the capacitance retention of 94% than SiO2:Ag 5 wt% (capacitance retention of 85%) after 1000 cycles at a current density of 1 A/g. These results may be attributed to the inherent characteristic of more silver nanoparticles present in the silica nanomatrix in SiO2:Ag 10 wt%. The intrinsic characteristic of rice hull-derived silica nanostructures such as high surface area and mesoporous structure along with the advantage of silver nanoparticles (conductivity) can facilitate the Faradic redox processes at electrode surface which are responsible for the supercapacitive behavior of the prepared silver-integrated silica nanostructures.

OBJECTIVES: The aim of this study is to study the electroactivity of zoledronic acid (ZOL), optimize the parameters affecting voltametric analysis of ZOL, and make a comparison between voltametric methods used to assay ZOL. MATERIALS AND METHODS: Three voltametric methods, cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV), were used to determine the concentrations of ZOL solutions (0.25(-1).2 mg.mL(-1)). Britton-Robinson universal buffer solutions (BRB) were used as supporting electrolytes with a glassy carbon working electrode. RESULTS: The calibration plots were linear in the range from 0.20 to 1.2 mg.mL(-1) for differential DPV and CV and from 0.09 to 1.2 mg.mL(-1) for SWV. DPV showed the highest correlation coefficient R(2) value of 0.993 and the lowest limit of detection (LOD) of 37.2 μg.mL(-1). Furthermore, DPV exhibited the highest precision with the lowest relative standard deviations (RSD) values. For a commercial product of ZOL, DPV showed the best accuracy and precision with 102.32% recovery and 2.88% RSD. CONCLUSION: ZOL is an electroactive compound. The pH of the BRB supporting the electrolyte is important for ZOL electroactivity. DPV is the recommended method for voltametric analysis of ZOL because of its high-performance regarding accuracy, precision, and LOD compared with other studied methods.

Diabetes is a common chronic disease, so it is particularly important to develop a convenient, fast, and highly sensitive non-enzymatic glucose sensor. In this work, a high sensitivity, low cost sensor was prepared on the substrate of printed circuit board. The nickel cobaltate (NiCo2O4) spherical nanomaterials were synthesized by facile hydrothermal and calcining methods. The working electrode was modified by NiCo2O4 nanospheres and the cation exchange resin in turn. Nafion cation exchange film can help to reduce the interference caused by surface-active compounds cyclic voltammetry- amperometric method was used to study the electrocatalytic performance of the sensor at room temperature. The sensor modified by NiCo2O4 nanospheres showed good sensor performance for glucose, including excellent sensitivity ( $3449.14~\mu \text{A}$ mM $^{-1}$ cm $^{-2}$ ), wide linear range ( $1~\mu \text{M}$ to 100 mM), and low detection limit ( $0.376~\mu \text{M}$ ). In addition, it has high selectivity, repeatability and stability. The sensor proposed in this work has been successfully applied to the detection of glucose in urine, and the results are consistent with the actual glucose concentration in urine.

Since the COVID-19 outbreak was declared a pandemic by the World Health Organization (WHO) in March 2020, ongoing efforts have been made to develop sensitive diagnostic platforms. Detection of viral RNA provides the highest sensitivity and specificity for detection of early and asymptomatic infections. Thus, this work aimed at developing a label-free genosensor composed of graphene as a working electrode that could be embedded into a flex printed circuit board (FPCB) for the rapid, sensitive, amplification-free and label-free detection of SARS-CoV-2. To facilitate liquid handling and ease of use, the developed biosensor was embedded with a user-friendly reservoir chamber. As a proof-of-concept, detection of a synthetic DNA strand matching the sequence of ORF1ab was performed as a two-step strategy involving the immobilization of a biotinylated complementary sequence on a streptavidin-modified surface, followed by hybridization with the target sequence recorded by the differential pulse voltammetric (DPV) technique in the presence of a ferro/ferricyanide redox couple. The effective design of the sensing platform improved its selectivity and sensitivity and allowed DNA quantification ranging from 100 fg/mL to $1~\mu \text{g}$ /mL. Combining the electrochemical technique with FPCB enabled rapid detection of the target sequence using a small volume of the sample (5- $20~\mu \text{L}$ ). We achieved a limit-of-detection of 100 fg/mL, whereas the predicted value was ~33 fg/mL, equivalent to approximately $5\times 10^{5}$ copies/mL and comparable to sensitivities provided by isothermal nucleic acid amplification tests. We believe that the developed approach proves the ability of an FPCB-implemented DNA sensor to act as a potentially simpler and more affordable diagnostic assay for viral infections in Point-Of-Care (POC) applications.

The application of electrochemical potentials to surfaces is an easy and direct way to alter surface charge density, the structure of the electrochemical double layer, and the presence of electrochemically activated species. On such electrified interfaces the formation of biofilms is reduced. Here we investigate how applied potentials alter the colonization of surfaces by the marine bacterium Cobetia marina and the marine diatom Navicula perminuta. Different constant potentials between -0.8 and 0.6 V as well as regular switching between two potentials were investigated, and their influence on the attachment of the two biofilm-forming microorganisms on gold-coated working electrodes was quantified. Reduced bacteria and diatom attachment were found when negative potentials and alternating potentials were applied. The results are discussed on the basis of the electrochemical processes occurring at the working electrode in artificial seawater as revealed by cyclic voltammetry.

The photoanode is one of the principal components in QDSSCs and its organization has an incredible influence on the cell performance. Here we report the investigations on the influence of photoanode material based on ZnO nanodot, nanorod, nanoplate, and nanoflower on the performance of CdSe quantum dot-sensitized solar cells. For the QDSSCs fabrication, a well-dispersed aqueous solution of 5 nm sized CdSe quantum was synthesized using the chemical method, and the working electrode was dipped for 10 h for adsorption of photosensitizer on ZnO nanostructures. The performance of the photoanode is further improved by surface modification of quantum dot by the introduction of a ZnS buffer layer using the SILAR method. The ZnS buffer layer on the surface of the CdSe quantum dot decreases the backscattering of charge carriers. The optimized number of SILAR cycles for maximum device efficiency was estimated for each photoanode cells. The obtained efficiencies were found to increase from 0.50 to 0.92% (4th cycle), 1.55% (3rd cycle), 2.69% (3rd cycle), and 3.05% (2nd cycle) for the ZnO nanodot, nanorod, nanoplate, and nanoflower-based CdSe QDSSCs, respectively. Better conversion efficiency was noticed for cells fabricated with ZnO nanoflower as photoanode using a minimum number of SILAR cycles. Improved photon scattering, multiple reflections, light harvesting, and higher electron lifetime lead to the enhancement of device performance. The results give an insight into the efficiency improvement strategies for QDSSCs with ZnO nanostructure-based photoanode.