Electrochem

The development of conductive coatings has significant implications for microelectronics and electrochemistry. However, conductive coatings may exhibit different electrochemical properties when prepared on different substrate materials. This research explores the comparative performance of graphene, graphene oxide (GO), and silver nanoparticle (Ag NP) composites as conductive coatings on diverse substrate materials, including polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and glass. The study employed various preparation methods, such as mixing conductive materials with substrate materials and preparing copolymer composite materials. The conductive coating approach was found to be the most straightforward and convenient, with broader development prospects and fewer restrictive conditions. The results indicate that the distinct surface characteristics of the substrate materials influence the conductive properties of coating materials. Consequently, results show that graphene exhibits the highest conductivity on all three substrates, while GO is more conductive than Ag NPs on PMMA and PDMS but less conductive than Ag NPs on glass. That offers valuable insights into the selection of substrate materials and coating materials for the preparation of conductive materials. Full article

An electrochemical bioassay based on rotating droplet electrochemistry by using an electron-transfer mediator was developed for the evaluation of a wide variety of pollutants such as antibiotics, heavy metals, and pesticides in the water environment. Ferricyanide was used as an electron-transfer mediator for obtaining the catalytic response of Escherichia coli. The electrochemical response of E. coli was measured via hydrodynamic chronoamperometry in a microdroplet on a screen-printed carbon electrode (SPCE). The constructed electrode system successfully evaluates the catalytic response of E. coli solution in the presence of ferricyanide. An assay for antibiotic toxicity on E. coli was carried out. The EC₅₀ for ampicillin, sulfamonomethoxine, chlorotetracycline, tetracycline, and oxytetracycline evaluated by the pre-incubation method were 0.26, 0.77, 5.25, 18.5, and 19.0 µM, respectively. The toxicity order was ampicillin > sulfamonomethoxine > chlorotetracycline > tetracycline > oxytetracycline. The proposed method can be used to evaluate the antibiotic toxicities in different real samples, such as pond water, powder, and raw milk. Recoveries were found in the range of 90 and 99%. The developed methods do not require additional incubation time to evaluate toxicity. Full article

Cu₂(ZnSn)(S)₄ (copper, zinc, tin, and sulfide (CZTS)) provides possible advantages over CuInGaSe2 for thin-film photovoltaic devices because it has a higher band gap. Preparing CZTS by electrodeposition because of its high productivity and lower processing costs, electroplating is appealing. Recently published studies reported that the electrodeposition process of CZTS still faces significant obstacles, such as the sulfur atomic ratio (about half of the whole alloy), deposits’ adhesion, film quality, and optical properties. This work introduces an improved bath that facilitates the direct electroplating of CZTS from one processing step. The precursors used were significantly more diluted than the typical baths mentioned in the last few years. An extensive analysis of the electrochemical behavior at various rotation speeds is presented at room temperature (~22 °C). The deposited alloy’s composition and adherence to the molybdenum back contact are examined with agitation. The annealing process was carried out in an environment containing sulfur, and the metal was not added at this stage. The ultimate sulfur composition was adjusted to 50.2%, about the desired atomic ratio. The compound’s final composition was investigated using the Energy-Dispersive X-ray Spectroscopy technique. Finally, X-ray diffraction analysis was applied to analyze CZTS crystallography and to measure thickness. Full article

Direct testing of pesticide contaminants in drinking water is a challenge. Portable and sensitive sensor platforms are desirable to test water contaminants directly at farm and consumer levels. In this study, we have demonstrated the feasibility of an electrochemical sensor for the direct detection of paraquat (PQ) in drinking water samples. An immunoassay-based sensing platform was fabricated using PQ-specific antibody immobilized on the surface of the electrochemically reduced graphene oxide (rGO) modified screen-printed carbon electrode (rGO-SPCE). Using non-faradaic electrochemical impedance spectroscopy (EIS) as a detection tool, the sensor platform demonstrated a dynamic response for PQ concentration in drinking water ranging from 0.05 ng/mL to 72.9 ng/mL (0.19 to 243.8 nM), with a coefficient of determination (r²) of 0.997 and a limit of detection of 0.05 ng/mL (0.19 nM). Percentage recovery within ±20% error was obtained, and the sensor cross-reactivity test showed a selective response against glyphosate antigen. With the flexibility to use single-frequency EIS and low sample volume, the developed sensor demonstrated testing in water samples directly without any sample pre-processing. This low-volume electroanalytical sensor platforms can be translated into portable testing tools for the detection of various water contaminants. Full article

Extracellular electron transfer (EET) by sulfate-reducing bacteria (SRB), such as Desulfovibrio ferrophilus IS5, enables bacterial interactions with minerals, which are vital for biogeochemical cycling and environmental chemistry. Here, we explore the direct EET mechanisms through outer-membrane cytochromes (OMCs) using IS5 as a model SRB. We employed nanostructured electrodes arrayed with 0, 50, 200, and 500 nm long nanowires (NWs) coated with indium–tin–doped oxide to examine the impact of electrode morphology on the direct EET efficacy. Compared to flat electrodes, NW electrodes significantly enhanced current production in IS5 with OMCs. However, this enhancement was diminished when OMC expression was reduced. Differential pulse voltammetry revealed that NW electrodes specifically augmented redox peaks associated with OMCs without affecting those related to redox mediators, suggesting that NWs foster direct EET through OMCs. Scanning electron microscopy observations following electrochemical analyses revealed a novel vertical cell attachment and aggregation on NW electrodes, contrasting with the horizontal monolayer cell attachment on flat electrodes. This study presents the first evidence of the critical role of electrode nanoscale topography in modulating SRB cell orientation and aggregation behavior. The findings underscore the significant influence of electrode morphology on the direct EET kinetics, highlighting the potential impact of mineral morphology on mineral reduction and biogeochemical processes. Full article

The escalating concern over environmental pollutants, particularly brominated flame retardants (BFRs), demands sophisticated detection methodologies for compounds like Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecane (HBCD). Amidst these challenges, advancements in electrochemical detection have notably focused on the integration of inorganic modifiers within carbon electrodes. Inorganic nanoparticles, known for their catalytic and surface-enhancing properties, play a pivotal role in augmenting the sensitivity and selectivity of electrode-based detection systems. These modifiers, encompassing materials such as graphene, CeO₂ nanocubes, and metal-organic frameworks, among others, have revolutionized the capabilities of carbon-based electrodes in accurately identifying specific BFRs. Full article

Battery-type hybrid supercapacitors (HSCs) (otherwise known as supercapatteries) are novel electrochemical energy storage devices bridge the gap between rechargeable batteries and traditional SCs. Herein, we report the synthesis of layered two-dimensional (2D) nickel disulfide (NiS₂) nanosheets (NSNs) modified with poly(3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) and their successful implementation in battery-type SCs. Initially, a layered 2D NSN is synthesized via a microwave-assisted hydrothermal method and further used as a template to coat PEDOT:PSS in order to prepare NiS₂@PEDOT:PSS nanocomposite electrodes by a facile drop-casting method. This is the first-time report on the synthesis of a hierarchical NiS₂@PEDOT:PSS nanocomposite electrode for battery-type HSC applications. An asymmetric battery-type HSC fabricated with NSN@PEDOT:PSS nanocomposite as positrode and activated carbon as negatrode delivers a maximum energy density of 52.1 Wh/kg at a current density of 1.6 A/g with a corresponding power density of 2500 W/kg. Full article

Ni–W alloys have received considerable interest as a promising structural material for microelectromechanical systems (MEMS) due to their exceptional properties, including hardness, ductility, corrosion resistance, and thermal stability. However, the electrodeposition of Ni–W alloys in the MEMS fabrication process to achieve intact structures with a thickness of several tens of micrometers is challenging due to the occurrence of cracking caused by side reactions and internal stresses during the electrodeposition process. To address this issue, our focus was on pulsed reverse electrodeposition (PRE) as a potential solution. The utilization of the PRE technique allows for a high concentration of reactive species on the electrode surface, thereby mitigating side reactions such as hydrogen generation. In this study, we examined the effects of the PRE method on the morphological characteristics, average crystal grain size, Vickers hardness, and micro-mechanical properties of Ni–W alloys. Full article

This work describes the fabrication and characterization of a new high surface area nanocomposite electrode containing reduced graphene oxide (rGO) and titanium nitride (TiN) for electrochemical applications. This approach involves electrochemically depositing rGO on a high surface area TiN nanorod array electrode to form a new nanocomposite electrode. The TiN nanorod array was first formed by the glancing angle deposition technique in a DC (Direct Current) sputtering system. GO flakes of ~1.5 μm in diameter, as confirmed by Dynamic Light Scattering (DLS), were electrodeposited on the nanostructured TiN electrode via the application of a fixed potential for one hour. The surface morphology of the as-prepared rGO/TiN electrode was evaluated by scanning electron microscopy (SEM) and the presence of rGO on TiN was confirmed by Raman Microscopy. The CV shows an increase in the capacitive current at rGO/TiN as compared to TiN. The rGO decorated TiN electrode was then used for analyzing the electrocatalytic oxidation of ascorbic acid and dopamine, and the reduction of nitrate by CV and linear sweep voltammetry (LSV), respectively. CV or LSV show that the electrochemical kinetics of these three analytes are significantly faster on rGO/TiN than TiN itself. Overall, the rGO/TiN electrode showed better electrochemical behavior for biomolecules like ascorbic acid and dopamine as well as another target analyte, nitrate ions, compared to TiN by itself. Full article

The influence of the component composition of coal batches and the final temperature of the coking process on the resistivity of coke was studied. Taking into account that the resistivity and reactivity are influenced by some common factors, such as the temperature level and coke readiness, which indicates the orderliness of its structure, the relationship between these indicators was established. The electrical resistivity can be considered a cumulative characteristic of coke properties, as evidenced by the mathematical dependencies of the change electrical resistance on the ash content, sulfur content, volatile yield, and petrographic composition. Analysis of the dependencies and their statistical evaluation indicate that the studied relationships are characterized by high values of correlation (0.6–0.84). The proposed regression equations can be recommended for optimizing the component composition and quality of production batches, given their significant impact on the resistivity of coke. This is especially relevant when coke is used in electrothermal processes, since the productivity and the electrical and thermal efficiency of the furnace depends on the resistivity of the coke in electrochemical processes in which carbon materials are used as anodes and lining elements and in the production of capacitor technology. As the resistivity test requires much less time to perform than the reactivity test, it can be considered as an alternative approach to the reactivity testing currently performed for quality control purposes. Full article

Electrochemical biosensors are valued for their sensitivity and selectivity in detecting biological molecules. Having the advantage of generating signals that can be directly or indirectly proportional to the concentration of the target analyte, these biosensors can achieve specificity by utilizing a specific biorecognition surface designed to recognize the target molecule. Electrochemical biosensors have garnered substantial attention, as they can be used to fabricate compact, cost-effective devices, making them promising candidates for point-of-care testing (POCT) devices. This study introduces a label-free electrochemical biosensor employing a gold screen-printed electrode (SPE) to detect lysophosphatidic acid (LPA), a potential early ovarian cancer biomarker. We employed the gelsolin–actin system, previously introduced by our group, in combination with fluorescence spectrometry, as a biorecognition element to detect LPA. By immobilizing a gelsolin–actin complex on an SPE, we were able to quantify changes in current intensity using cyclic voltammetry and differential pulse voltammetry, which was directly proportional to the LPA concentration in the solution. Our results demonstrate the high sensitivity of the developed biosensor for detecting LPA in goat serum, with a limit of detection (LOD) and a limit of quantification (LOQ) of 0.9 µM and 2.76 µM, respectively, highlighting its potential as a promising tool for early-stage diagnosis of ovarian cancer. Full article

In the present study, LiFePO₄/CNF self-standing cathodes for LIBs are synthesized by electrospinning. A lower active material amount (12.3 and 34.5 wt%) is used, compared to the conventional tape-casted cathodes (70–85 wt%). The characterization techniques (XRPD, SEM, TEM, EDS, Raman spectroscopy, and thermogravimetry) confirm that the olivine-type structure of LiFePO₄ is maintained in the binder-free electrodes, and the active material is homogeneously dispersed into and within the carbon nanofibers. The electrochemical investigation demonstrates that higher Li⁺ diffusion coefficients (1.36 × 10⁻¹¹ cm²/s) and improved reversibility are reached for free-standing electrodes, compared to the LiFePO₄ tape-casted cathode (80 wt% of active material) appositely prepared for comparison. The 34.5 wt% LiFePO₄ self-standing cathode displays a lower capacity fading, good reversibility and stability, enhanced capacity values at C-rates higher than 5C, and a good lifespan when cycled 1000 cycles at 1C and further cycled up to 20C, compared to the tape-casted counterpart. Notably, the improved electrochemical performances are obtained by only the 34.5 wt% of active material. The results evidence the relevant role of the CNF matrix suitable to host LiFePO₄, to promote electrolyte permeation and contact with the active material, and to increase the electronic conductivity. Full article

This study reports on the use of supercritical CO₂ (scCO₂) for the metallization of ultrahigh-molecular-weight polyethylene (UHMW-PE) filaments, which are used as functional components in weavable devices. UHMW-PE is well known for its chemical and impact resistance, making it suitable for use in bulletproof clothing and shields. However, its chemical resistance poses a challenge for metallization. By utilizing scCO₂ as the solvent in the catalyzation process, a uniform and defect-free layer of Ni-P is successfully deposited on the UHMW-PE filaments. The deposition rate of Ni-P is enhanced at higher temperatures during the scCO₂ catalyzation. Importantly, the durability of the Ni-P-metalized UHMW-PE filaments is improved when the scCO₂ catalyzation is carried out at 120 °C, as evidenced by minimal changes in electrical resistivity after a rolling test. Full article

Food quality assessment is becoming a global priority due to population growth and the rise of ionic pollutants derived from anthropogenic sources. However, the current methods used to quantify toxic ions are expensive and their operation is complex. Consequently, there is a need for affordable and accessible methods for the accurate determination of ion concentrations in food. Electrochemical sensors based on potentiometry represent a promising approach in this field, with the potential to overcome limitations of the currently available systems. This review summarizes the current advances in the electrochemical quantification of heavy metals and toxic anions in the food industry using potentiometric sensors. The healthcare impact of common heavy metal contaminants (Cd²⁺, Hg²⁺, Pb²⁺, As³⁺) and anions (ClO₄⁻, F⁻, HPO₄⁻, SO₄²⁻, NO₃⁻, NO₂⁻) is discussed, alongside current regulations, and gold standard methods for analysis. Sensor performances are compared to current benchmarks in terms of selectivity and the limit of detection. Given the complexity of food samples, the percentage recovery values (%) and the methodologies employed for ion extraction are also described. Finally, a summary of the challenges and future directions of the field is provided. An overview of technologies that can overcome the limitations of current electrochemical sensors is shown, including new extraction methods for ions in food. Full article

The ability of a diagnosis tool to observe an abnormal state of a system remains a major issue for health monitoring. For that purpose, several diagnosis tools have been proposed in the literature. Most of them are developed for specific system characterization, and the genericity of the approaches is not considered. Indeed, most approaches proposed in the literature are based on an expert offline consideration that makes it hard to apply the strategy to other systems. It is therefore important to develop a diagnostic tool that takes as little as possible expert knowledge to reduce the dependency between the tool and the system. This paper, therefore, focuses on the application of a generic diagnosis tool on an open cathode fuel cell. The goal is to feed the diagnosis algorithm with a voltage measurement and let it proceed to a self-clustering of the signal components. Each cluster’s interpretation remains to be established by the expert point of view that is then involved downstream of the diagnosis tool. Full article

Electrochemistry is a hotspot in today’s research arena. Many different domains have been extended for their role towards the Internet of Things, digital health, personalized nutrition, and/or wellness using electrochemistry. These advances have led to a substantial increase in the power and popularity of electroanalysis and its expansion into new phases and environments. The recent COVID-19 pandemic, which turned our lives upside down, has helped us to understand the need for miniaturized electrochemical diagnostic platforms. It also accelerated the role of mobile and wearable, implantable sensors as telehealth systems. The major principle behind these platforms is the role of electrochemical immunoassays, which help in overshadowing the classical gold standard methods (reverse transcriptase polymerase chain reaction) in terms of accuracy, time, manpower, and, most importantly, economics. Many research groups have endeavoured to use electrochemical and bio-electrochemical tools to overcome the limitations of classical assays (in terms of accuracy, accessibility, portability, and response time). This review mainly focuses on the electrochemical technologies used for immunosensing platforms, their fabrication requirements, mechanistic objectives, electrochemical techniques involved, and their subsequent output signal amplifications using a tagged and non-tagged system. The combination of various techniques (optical spectroscopy, Raman scattering, column chromatography, HPLC, and X-ray diffraction) has enabled the construction of high-performance electrodes. Later in the review, these combinations and their utilization will be explained in terms of their mechanistic platform along with chemical bonding and their role in signal output in the later part of article. Furthermore, the market study in terms of real prototypes will be elaborately discussed. Full article

A silicon nanoparticle–graphite nanosheet composite was prepared via a facile ball milling process for use as the anode for high-rate lithium-ion batteries. The size effect of Si nanoparticles on the structure and on the lithium-ion battery performance of the composite is evaluated. SEM and TEM analyses show a structural alteration of the composites from Si nanoparticle-surrounded graphite nanosheets to Si nanoparticle-embedded graphite nanosheets by decreasing the size of Si nanoparticles from 250 nm to 40 nm. The composites with finer Si nanoparticles provide an effective nanostructure containing encapsulated Si and free space. This structure facilitates the indirect exposure of Si to electrolyte and Si expansion during cycling, which leads to a stable solid–electrolyte interphase and elevated conductivity. An enhanced rate capability was obtained for the 40 nm Si nanoparticle–graphite nanosheet composite, delivering a specific capacity of 276 mAh g⁻¹ at a current density of 1 C after 1000 cycles and a rate capacity of 205 mAh g⁻¹ at 8 C. Full article

The possibility of using Si-based anodes in lithium-ion batteries is actively investigated due to the increased lithium capacity of silicon. The paper reports the preparation of submicron silicon fibers on glassy carbon in the KI–KF–KCl–K₂SiF₆ melt at 720 °C. For this purpose, the parameters of silicon electrodeposition in the form of fibers were determined using cyclic voltammetry, and experimental samples of ordered silicon fibers with an average diameter from 0.1 to 0.3 μm were obtained under galvanostatic electrolysis conditions. Using the obtained silicon fibers, anode half-cells of a lithium-ion battery were fabricated, and its electrochemical performance under multiple lithiations and delithiations was studied. By means of voltametric studies, it is observed that charging and discharging the anode based on the obtained silicon fibers occurs at potentials from 0.2 to 0.05 V and from 0.2 to 0.5 V, respectively. A change in discharge capacity from 520 to 200 mAh g⁻¹ during the first 50 charge/discharge cycles at a charge current of 0.1 C and a Coulombic efficiency of 98–100% was shown. The possibility of charging silicon-based anode samples at charging currents up to 2 C was also noted; the discharge capacity ranged from 25 to 250 mAh g⁻¹. Full article

Determining the oxidation potential (OP) of lithium-ion battery (LIB) electrolytes using theoretical methods will significantly speed up and simplify the process of creating a new generation high-voltage battery. The algorithm for calculating OP should be not only accurate but also fast. Our work proposes theoretical principles for evaluating the OP of LIB electrolytes by considering LiDFOB solutions with different salt concentrations in EC/DMC solvent mixtures. The advantage of the new algorithm compared to previous versions of the theoretical determination of the oxidation potential of electrolyte solutions used in lithium-ion batteries for calculations of statistically significant complexes, the structure of which was determined by the molecular dynamics method. This approach significantly reduces the number of atomic–molecular systems whose geometric parameters need to be optimized using quantum chemical methods. Due to this, it is possible to increase the speed of calculations and reduce the power requirements of the computer performing the calculations. The theoretical calculations included a set of approaches based on the methods of classical molecular mechanics and quantum chemistry. To select statistically significant complexes that can make a significant contribution to the stability of the electrochemical system, a thorough analysis of molecular dynamics simulation trajectories was performed. Their geometric parameters (including oxidized forms) were optimized by QM methods. As a result, oxidation potentials were assessed, and their dependence on salt concentration was described. Here, we once again emphasize that it is difficult to obtain, by calculation methods, the absolute OP values that would be equal (or close) to the OP values estimated by experimental methods. Nevertheless, a trend can be identified. The results of theoretical calculations are in full agreement with the experimental ones. Full article