Search Results (308)

This study presents a comprehensive evaluation and an equivalent circuit modeling of the skin–electrode impedance characteristics of three types of ultra-thin tattoo electrodes, all based on Parylene C nanofilms but with different active materials: Gold, Silver, and PEDOT:PSS. Their performance was compared to standard disposable Ag/AgCl electrodes. Impedance measurements were carried out on six human subjects under controlled conditions, assessing the frequency response in the range of 20 Hz to 1 kHz. For each subject, the impedance was recorded six times over one hour to investigate the stability and the temporal performance. The collected data were subsequently analyzed to model the electrical properties and interface behavior of each electrode type. The findings demonstrate that the tattoo electrodes offer impedance levels comparable to those of Ag/AgCl electrodes (in the order of tens of kΩ at 20 Hz), while providing additional benefits such as enhanced conformability, improved skin adhesion, and reduced skin irritation during use. Furthermore, the modeling of the skin–electrode interface through a more detailed equivalent circuit than the single time constant model enables a more detailed interface analysis and description, with fitting algorithm R² scores of about 0.999 and 0.979 for the impedance magnitude and impedance phase, respectively. The proposed equivalent circuit offers valuable insights for optimizing electrode design, supporting the potential of Parylene C-based tattoo electrodes as promising alternatives for next-generation wearable bioelectronic applications. Full article

Adipic acid (AA), a pivotal precursor for nylon-6,6 and polyurethane, was synthesized via an innovative catalytic electrocatalytic oxidation strategy in this study. Four distinct MnO_x/CNT nanocatalysts were prepared by hydrothermal and co-precipitation methods and fabricated into electrodes for the oxidation of cyclohexanol (Cy-OH) in a K₂SO₄ neutral solution. Comprehensive characterization revealed that the catalytic performance depended on both crystalline phase configuration and manganese valence states. MnO(OH) and MnO_x were identified as the main active species, with the synergy between MnO species and carbon nanotubes significantly enhancing catalytic activity. Mechanistic investigations demonstrated that under Mn⁴⁺-dominant conditions, low-valence manganese species facilitated Cy-OH-to-cyclohexanone (Cy=O) conversion, while an optimal O_ads/O_lat ratio (≈1) effectively promoted subsequent Cy=O oxidation to AA. Under optimized conditions (1.25 V vs. Ag/AgCl, 80 °C, 15 h), complete Cy-OH conversion was achieved with 56.4% AA yield and exceptional Faradaic efficiency exceeding 94%. This work elucidates manganese-based electrocatalytic oxidation mechanisms, proposes a sequential reaction pathway, and establishes an environmentally benign synthesis protocol for AA, advancing sustainable industrial chemistry. Full article

In enzymatic reaction glucose detection chips, the enzyme can easily dislodge from the electrode, which harms both the chip and test stability. Additionally, enzyme activity significantly decreases at low temperatures. Consequently, immobilizing the enzyme at the appropriate substrate and ambient temperature is a critical step for improving the chip. To address this issue, an electrochemical detection chip was modified using the nanomaterial MXene, known for its large specific surface area, excellent adsorption, good dispersion, and high conductivity. Meanwhile, AgNO₃ solution was added to the Ti₃C₂T_x MXene nanosheet solution, and the AgNP@MXene material was prepared by heating in a water bath. This process further enhances photothermal conversion efficiency due to the localized surface plasmon resonance effect of silver nanoparticles and MXene. This MXene-based photothermally enhanced paper chip exhibits outstanding photothermal conversion performance and sensitive photoelectrochemical responsiveness, along with good cycling stability. Moreover, improved glucose detection sensitivity at low winter temperatures has been achieved, and the ambient temperature range of the paper chip has been expanded to 25–37 °C. Full article

To solve the problems of carbon fiber (CF) electrodes, including poor frequency response and large potential drift, CFs were subjected to a roughening pretreatment process combining thermal oxidation and electrochemical anodic oxidation and then modified with Ag nanoparticles (AgNPs) using electroplating to prepare a CF electric field sensor. The surface morphology of the as-prepared AgNP-CF electric field sensor was characterized via optical microscopy, scanning electron microscopy, XPS, and energy-dispersive spectroscopy, and its impedance, polarization drift, self-noise, and temperature drift values were determined. Results show that the surface modification of the AgNP-CF electric field sensor is uniform, and its specific surface area is considerably increased. The electrode potential drift, characteristic impedance, self-noise, and temperature drift are 52.1 µV/24 h, 3.6 Ω, 2.993 nV/√Hz@1 Hz, and less than 70 µV/°C, respectively. Additionally, the AgNP-CF electric field sensor demonstrates low polarization and high stability. In field and simulated ocean tests, the AgNP-CF electrode exhibits excellent performance in the field and underwater environments, which renders it promising for the measurement of the ocean and geoelectric fields owing to its advantages, such as low noise and high stability. Full article

To quantitatively describe the frequency domain spectroscopy (FDS) characteristics of transformer oil-paper insulation under varying temperature, moisture, and aging conditions, a modified Cole–Cole model is introduced. This model decomposes the dielectric spectrum into polarization, DC conduction, and hopping conduction components, with parameters reflecting insulation characteristics. Methods for determining initial parameter values and optimizing the objective function are proposed. Using a three-electrode setup, FDS measurements were conducted on oil-paper insulation samples at different temperatures, and extracted parameters were analyzed for their variation patterns. Within the frequency range of 1.98 × 10⁻⁴ Hz to 1 × 10³ Hz, the model achieves a goodness-of-fit (R²) exceeding 0.97 for both real and imaginary permittivity components, with the sum of squared errors reduced from 259 to 57.35 at 70 °C, outperforming the fundamental Cole–Cole and Ekanayake’s models. Temperature significantly affects the relaxation and DC conductivity components; both adhere to the Arrhenius equation, enabling precise condition assessment of transformer insulation. Full article

This study presents the successful fabrication of lead zirconate titanate (PZT) thin films on silicon (Si) substrates using a hybrid deposition method combining spin-coating and RF sputtering techniques. Initially, a PZT layer was deposited through four successive spin-coating cycles, followed by an additional layer formed via RF sputtering. The resulting multilayer structure was annealed at ${700 }^{°}$C for 2 h to improve crystallinity. Comprehensive material characterization was conducted using XRD, SEM, cross-sectional SEM, EDX, and UV–VIS absorbance spectroscopy. The analyses confirmed the formation of a well-crystallized perovskite phase, a uniform surface morphology, and an optical band gap of approximately 3.55 eV, supporting its suitability for sensing applications. Building upon these findings, a multilayer PZT-based touch sensor was fabricated and electrically characterized. Low-frequency I–V measurements demonstrated consistent and repeatable polarization behavior under cyclic loading conditions. In addition, $\left|Z\right|$–f measurements were performed to assess the sensor’s dynamic electrical behavior. Although expected dielectric responses were observed, the absence of distinct anti-resonance peaks suggested non-idealities linked to ${\mathrm{Ag}}^{+}$ ion diffusion from the electrode layers. To account for these effects, the classical Butterworth–Van Dyke (BVD) equivalent circuit model was extended with additional inductive and resistive components representing parasitic pathways. This modified model provided excellent agreement with the measured impedance and phase data, offering deeper insight into the interplay between material degradation and electrical performance. Overall, the developed sensor structure exhibits strong potential for use in piezoelectric sensing applications, particularly for tactile and pressure-based interfaces. Full article

This paper investigates the measurement capability, dynamic response, and mechanical reliability of all 3D-printed multi-material thermistors. The thermistor design consisted of three main components: a polycarbonate (PC) substrate, a silver (Ag) electrode pair, and a poly(3,4-ethylenedioxythophene):poly(4-styrenesulfonate) (PEDOT:PSS) thermosensitive layer. The thermistors were fabricated using two manufacturing techniques: fused deposition modeling (FDM) for the substrate and micro-dispensing for the Ag and PEDOT:PSS films. Two designs with different sensing areas, D1 (90 mm²) and D2 (54 mm²), were fabricated. As the indicator of measurement capability, the highest thermal indexes were recorded as 905.64 and 813.03 K for D1 and D2 thermistors, respectively. Thermistors exhibited comparable dynamic performance, with normalized resistance variations ranging from 0.96 to 1 for temperature changes between 25 and 45 °C. The sensing area influenced both measurement capability and dynamic performance, where larger sensing areas enhanced measurement capability but extended the time required to complete dynamic cycles, around 400 s for D1 versus 350 s for D2. Adhesion tests revealed a strong bonding between the PEDOT:PSS and Ag layer with less than 5% material removal. However, the adhesion of the PEDOT:PSS to the PC substrate was weak, with over 65% material removal. Morphological analysis indicated that the poor adhesion was caused by suboptimal surface properties of the 3D-printed substrate, even resulting in gaps between these two surfaces. This study demonstrates that our all 3D-printed multi-material thermistors can match reported measurement performance with an acceptable dynamic performance while highlighting the need to improve 3D-printed substrate surface properties to enhance the performance of such multi-material structures. Full article

The core challenge of integrated carbon capture and utilization (ICCU) technology lies in developing electrolytes that combine efficient carbon dioxide (CO₂) capture with electrocatalytic conversion capabilities. This review analyzes the structure–performance relationship between electrolyte properties and CO₂ electrochemical reduction (eCO₂RR), revealing the key regulatory mechanisms. Research shows that the performance of bicarbonate electrolytes heavily depends on the cation type, where Cs⁺ can achieve over 90% CO selectivity by suppressing the hydrogen evolution reaction (HER) and stabilizing reaction intermediates, though its strong corrosiveness limits practical applications. Although amine absorbents excel in carbon capture (efficiency > 90%), they tend to undergo competitive adsorption during electrocatalysis, making formic acid the primary product (FE = 15%); modifying electrodes with ionomers can enhance their activity by 1.15 times. Ionic liquids (ILs) demonstrate unique advantages due to their tunability: imidazolium-based ILs improve formate selectivity to 85% via carboxylate intermediate formation, while amino-functionalized task-specific ILs (TSILs) achieve a 1:1 stoichiometric CO₂ absorption ratio. Recent breakthroughs reveal that ternary IL hybrid electrolytes can achieve nearly 100% CO Faradaic efficiency (FE) through microenvironment modulation, while L-histidine additives boost CH₄ selectivity by 23% via interface modification. Notably, constructing a “bulk acidic–interfacial neutral” pH gradient system addresses carbonate deposition issues in traditional alkaline conditions, increasing C₂₊ product efficiency to 50%. Studies also highlight that cation–anion synergy (e.g., K⁺/I⁻) significantly enhances C-C coupling through electrostatic interactions, achieving 97% C₂₊ selectivity on Ag electrodes. These findings provide new insights for ICCU electrolyte design, with future research focusing on machine learning-assisted material optimization and reactor engineering to advance industrial applications. Full article

Sodium-ion batteries present an economical energy storage solution, yet their anode kinetics remain slow, impeding rate performance and cyclability. Layered FeSe anodes, characterized by metallic conductivity, hold potential, but structural decay and insufficient active sites during cycling continue to pose challenges. Herein, these challenges are addressed through the implementation of dual Ni doping and Se vacancy engineering in FeSe@C to synergistically regulate cationic/anionic configurations. The ionic substitution of larger Fe²⁺ ions (0.78 Å ionic radius) with smaller Ni²⁺ ions (0.69 Å) induces lattice distortion and generates abundant Se vacancies, enhancing electron transport, active site accessibility, and Na⁺ adsorption. These synergistic modifications effectively boost Na⁺ diffusion kinetics and electrolyte compatibility, creating a favorable electrochemical environment for fast sodium storage. Consequently, the optimized 2%Ni-FeSe@C electrode retains an exceptional discharge specific capacity of 307.67mAh g⁻¹ after 1000 cycles at an ultrahigh current density of 5 Ag⁻¹, showcasing superior rate capability and long-term cycling stability, paving the way for practical high-power SIBs. Full article

Carbon nanofibrous materials from electrospinning are good candidate electrode materials for supercapacitor applications due to their straightforward processability, chemical stability, high porosity, and large surface area. In this research, a straightforward and effective way was revealed to significantly enhance the electrochemical performance of carbon nanofibrous electrode material from electrospinning of polyacrylonitrile (PAN). Fluorination of the electrospun carbon nanofibers (ECNF) was studied by comparing two types of hydrofluoric acid (HF) treatment, i.e., direct HF acid treatment on ECNF (Type I) vs. HF acid treatment on the stabilized PAN (Type II) followed by carbonization. The latter was found to be an advantageous way to introduce C-F bonds in the resultant carbon nanofibrous electrode material that contributed to pseudocapacitance. Furthermore, the Type II HF acid treatment demonstrated exciting synergistic effects with ECNF aerogel formation on carbon structure and porosity development and generated a superior fluorinated electrospun carbon nanofibrous aerogel (ECNA-F) electrode material for supercapacitor uses. The resultant ECNA-F electrode material demonstrated excellent electrochemical performance with great cyclic stability due to the large improvements in both pseudocapacitance and electrical double-layer capacitance. ECNA-F achieved a specific capacitance of 372 F/g at a current density of 0.5 A/g with 1 M H₂SO₄ electrolyte, and the device with ECNA-F and 1 M Na₂SO₄ electrolyte possessed an energy density of 29.1 Wh/kg at a power density of 275 W/kg. This study provided insight into developing high-performance and stable carbon nanofibrous electrode materials for supercapacitors. Full article

Aging experiments are pivotal for car manufacturers to ensure the reliability of their battery cells. However, realistic aging methods are time-consuming and resource-intensive, necessitating accelerated aging techniques. While these techniques reduce testing time, they can also lead to distorted results due to the partially reversible nature of cell behavior, which stems from the inhomogenization and rehomogenization of conducting salt and lithium distribution in the electrode. To accurately capture these phenomena, cell relaxation must be incorporated into the test design. This work investigates the impact of the test procedure and several stress factors, namely depth of discharge and C- rate, on the formation and rehomogenization of cell inhomogeneities. The experimental results reveal increasing cell inhomogenization, leading to growing reversible capacity losses, particularly under conditions with shorter cycling interruptions (check ups and rest phases). These reversible capacity losses are associated with a significant reduction in cycle life performance of up to 400% under identical cycling conditions but shorter cycling interruptions. Similar trends are observed for increasing cycle depths and C-rates. Optimized recovery cycles effectively mitigate cell inhomogenization, doubling cycle stability without requiring considerable additional testing time. Furthermore, a clear correlation is found between increasing inhomogenization and cell failure, with lithium stripping confirming the occurrence of lithium plating shortly before failure. These findings emphasize the critical importance of considering cell relaxation in cycle aging studies to ensure reliable and accurate lifetime predictions. Under realistic conditions, substantially enhanced cycle stability is expected. Full article

Silver-white, matte, smooth, and durable deposits of silver-rhenium, with thicknesses ranging from 2.0 to 13.7 μm and containing 0.15 to 13.5 wt.% Re, were obtained with a current efficiency of 66–98% from a developed dicyanoargentate–perrhenate bath based on a borate–phosphate–carbonate silver-plating electrolyte. This study was focused on the influence of bath composition, the [Ag(I)]:[ReO₄⁻] ratio, surfactant additives, applied current density, temperature, and stirring, on the alloys’ composition, structure, morphology, microhardness, adhesion, and porosity. A voltammetric analysis was conducted, considering the influence of ethanolamines on electrode processes. In baths with triethanolamine (TEA), coatings similar to a silver matrix with rhenium doped in mass fractions are likely achievable. Monoethanolamine (MEA) is recommended due to its process-activating properties. All coatings were nanocrystalline (τ = 28.5–35 nm). For deposits containing less than 10 wt.% Re, characteristic silver XRD peaks were observed, while for other deposits, additional peaks attributed probably to Re(VII) and Re(VI) oxides. A linear relationship H_v − τ^−1/2, typical for Hall–Petch plots, was obtained, confirming that grain boundaries play a crucial role in mechanical properties of coatings. The conditions for stable electrochemical synthesis of promising functional Ag-Re coatings of predetermined composition (0.7–1.5 wt.% Re) were proposed for practical use in power electronics and energy sectors for manufacturing electrical contacts operating across a wide temperature range. This was realized by deposition from an Ag-rich bath in the area of mixed electrochemical kinetics, at potential values corresponding to the region of half the limiting current: j = 2.5–6 mA cm⁻², t = 19–33 °C. Full article

This study successfully demonstrates the synthesis of foxtail millet carbon-activated (FMCA) materials using a two-step carbonization process from foxtail millet husk (FMH). The pre-carbonized biomass-derived millet husk was chemically activated with KOH at 500 °C and subsequently carbonized in an inert argon atmosphere at 800 °C in a tubular furnace. XRD analysis revealed a diffraction peak at 2θ = 23.67°, corresponding to the (002) plane, indicating the presence of graphitic structures. The Raman analysis of FMCA materials showed an intensity ratio (I_G/I_D) of 1.13, signifying enhanced graphitic ordering and structural stability. The as-prepared FMC and FMCA electrode materials demonstrate efficient charge storage electrochemical symmetric devices. Electrochemical analysis revealed the charge–discharge curves and a specific capacitance of Csp (FMC//FMC) 55.47 F/g and (FMCA//FMCA) 82.94 F/g at 0.5 A/g. Additionally, the FMCA//FMCA symmetric device exhibits superior performance with a higher capacity retention of 94.89% over 5000 cycles. The results confirm the suitability of FMCA for energy storage applications, particularly in electrochemical double-layer capacitors (EDLCs), making it a promising material for next-generation supercapacitors. Full article

Cytomegalovirus (CMV) infection in pregnant women is one of the most common causes of congenital infection in children. It is often asymptomatic but can lead to serious complications, including progressive sensorineural hearing loss. Profound hearing loss is an indication for cochlear implantation (CI). Electrode impedance and neural response telemetry (NRT) thresholds can be measured to confirm correct electrode placement and speech processor programming. Background/Objectives: The aim of the study is to evaluate the hearing outcome of children with profound sensorineural hearing loss or deafness due to cCMV infection after CI compared to a control group of children born with other causes of congenital hearing loss and to identify prognostic factors predicting the outcome of patients with hearing loss due to cCMV infection after CI. Methods: A retrospective study was conducted in patients implanted between 2016 and 2023 at the Department of Otolaryngology of the Institute of the Polish Mother’s Memorial Hospital Research Institute in Łódź. Pre- and postoperative hearing levels, electrode impedance and neural response telemetry (NRT) thresholds were compared. The degree of pre-implantation hearing loss was assessed by the level of the recorded V-wave in the ABR test. Post-implantation hearing assessment was based on the last available free-field tonal audiometry measurement. Impedance measurements were included: intraoperative, 1, 6, 12 months after CI, respectively, and NRT thresholds. Results: The final analysis included 84 patients with profound sensorineural hearing loss and complete audiological follow-up data: 13 patients with congenital CMV (cCMV) infection and 71 patients with other causes of deafnes. The analysis included 175 implanted ears: 17 in the CMV group and 158 in the control group. The age at implantation ranged from 1 to 11 years in the CMV and from 1 to 13 years in the control group. Mean preoperative hearing thresholds were 94.54 dB in the CMV group and 97.04 dB in the control group. At the most recent postoperative evaluation, mean thresholds improved to 33.83 dB and 36.42 dB, respectively. No statistically significant differences were observed between the groups. Mean intraoperative NRT values were 79.74 in the CMV group and 86.90 in the non-CMV group. Final NRT values were 129.77 and 130.76, respectively. Mean impedance values measured intraoperatively and at 1, 6 and 12 months postoperatively were 11.09 kOhm, 13.40 kOhm, 8.35 kOhm and 8.25 kOhm in the CMV group; and 12.28 kOhm, 14.06 kOhm, 9.60 kOhm and 8.00 kOhm in the control group, respectively. Conclusions: CI in children with deafness caused by cCMV infection is an effective treatment option. Initial electrical impedance values of the electrodes increase after implant activation and decrease in subsequent months of follow-up, suggesting the absence of active adhesion processes in the cochlea. Full article

The wide operating temperature and voltage window are favourable properties that increase the practical applications of supercapacitors. Ionic liquids (IL) are suitable electrolytes that allow supercapacitors to be used in wide operating ranges. In this study, triethylammonium tetrafluoroborate (Et₃NHBF₄) is tested as a new IL to operate supercapacitors in a wide temperature range (−40 °C, 25 °C, and 80 °C) in the presence of commercial activated carbon. The performance of Et₃NHBF₄ is compared to two different commercial ILs. This study also investigates the application of heat treatment to determine suitable activated carbon surface characteristics for ILs. The results indicate that heat treatment enhances the electrode–electrolyte interaction, and the electrochemical performances of the supercapacitors prepared from the heat-treated activated carbon are significantly higher than the original commercial activated carbon. Electrochemical tests show that the synthesised Et₃NHBF₄ (with propylene carbonate) can be used over a wide temperature range and has a better energy storage performance, especially at −40 °C (specific capacitance of 42.12 F/g at 2 A/g), compared to the other two commercial ionic liquids. Full article