Search Results (16)

To address the limitations of conventional electrochemical impedance spectroscopy (EIS) testing, we propose an efficient rapid EIS testing system. This system utilizes an AC pulse excitation signal combined with an “intelligent fast fourier transform (IFFT) optimization algorithm” to achieve rapid “one-to-many” impedance data measurements. This significantly enhances the speed, flexibility, and practicality of EIS testing. Furthermore, the conventional model-fitting approach for EIS data often struggles to resolve the issue of overlapping impedance arcs within a limited frequency range. To address this, the present study employs the Regularization Distributed Relaxation Time (RDRT) method to process EIS data obtained under AC pulse conditions. This approach avoids the workload and analytical uncertainties associated with assuming equivalent circuit models. Finally, the practical utility of the proposed testing system and the RDRT impedance analysis method is demonstrated through the estimation of battery state of health (SOH). In summary, the method proposed in this study not only addresses the issues associated with conventional EIS data acquisition and analysis but also broadens the methodologies and application scope of EIS impedance testing. This opens up new possibilities for its application in fields such as lithium-ion batteries (LIBs) energy storage. Full article

Fuel cells, as clean and efficient energy conversion devices, hold great potential for applications in the fields of hydrogen-based transportation and stand-alone power systems. Due to their sensitivity to load parameters, environmental parameters, and gas supply, the performance monitoring and fault diagnosis of fuel cell systems have become crucial research areas. Electrochemical impedance spectroscopy (EIS) is a widely applied analytical method in fuel cell systems. that can provide rich information about dynamic system responses, internal impedance, and transmission characteristics. Currently, EIS detection is primarily implemented by using simple topologies such as boost circuits. However, the injection of excitation signals often results in significant power fluctuations, leading to issues such as uneven temperature distributions within the cell, unstable gas supply, and damage to the proton exchange membrane. To address this issue, this paper proposes a real-time EIS detection technique for a proton exchange membrane fuel cell (PEMFC) system that connects a lithium-ion battery and injects the load voltage perturbation through a triple active bridge (TAB) converter. By applying the small-signal model of the TAB converter and designing a system controller using a decoupling control method, the PEMFC power remains stable after the disturbance injection across the entire frequency range under tests. Furthermore, the lithium-ion battery can instantly track load changes during fluctuations. The proposed EIS detection method can acquire EIS data in real time to monitor the state of the PEMFC. Simulation results validate the effectiveness and accuracy of the proposed method for EIS detection. Full article

Background: Specifically designed peptide mimetics offer higher selectivity regarding their toxicity to mammalian cells. In addition to the α-helix conformation, the specific activity is related to the peptide’s ability to penetrate the cell membrane. The alterations in lipid membrane properties were addressed in the presence of the peptide KLAKLAK-NH₂ and analogs containing β-alanine, strengthening the antibacterial activity and/or naphtalimide with proven anticancer properties. Methods: The molecular interactions of the peptide mimetics with POPC bilayers were studied using FTIR-ATR spectroscopy. The thermal shape fluctuation analysis of quasispherical unilamellar vesicles was applied to probe the membrane bending elasticity. The impedance characteristics of bilayer lipid membranes were measured using fast Fourier-transform electrochemical impedance spectroscopy. Results: A lateral peptide association with the membrane is reported for β-alanine-containing peptides. The most pronounced membrane softening is found for the NphtG-KLβAKLβAK-NH₂ analog containing both active groups that corroborate with the indications for 1,8-naphthalimide penetration in the lipid hydrophobic area obtained from the FTIR-ATR spectra analysis. The β-alanine substitution induces strong membrane-rigidifying properties even at very low concentrations of both β-alanine-containing peptides. Conclusions: The reported results are expected to advance the progress in tailoring the pharmacokinetic properties of antimicrobial peptides with strengthened stability towards enzymatic degradation. The investigation of the nonspecific interactions of peptides with model lipid membranes is featured as a useful tool to assess the antitumor and antimicrobial potential of new peptide mimetics. Full article

Carbon nanotubes are a promising material for use in innovative biomedical solutions due to their unique chemical, mechanical, electrical, and magnetic properties. This work provides a method for the development of ultrasonically assisted electrophoretic deposition of multi-walled carbon nanotubes on a CoCrMo dental alloy. Functionalization of multi-walled carbon nanotubes was carried out by chemical oxidation in a mixture of nitric and sulfuric acids. The modified and unmodified multi-walled carbon nanotubes were anaphoretically deposited on the CoCrMo alloy in an aqueous solution. Chemical composition was studied by Fourier transform infrared spectroscopy. Surface morphology was examined by scanning electron microscopy. The mechanism and kinetics of the electrochemical corrosion of the obtained coatings in artificial saliva at 37 °C were determined using the open-circuit potential method, electrochemical impedance spectroscopy, and anodic polarization curves. The capacitive behavior and high corrosion resistance of the tested electrodes were revealed. It was found that the kinetics of electrochemical corrosion of the CoCrMo electrode significantly decreased in the presence of the functionalized multi-walled carbon nanotube coating. Electrophoretic deposition was shown to be an effective, low-cost, and fast method of producing nanotubes with controlled thickness, homogeneity, and packing density. Full article

To achieve fast testing of the barrier properties of organic coatings, immersion tests, AC-DC-AC tests, and coupled tests of AC-DC-AC with hydrostatic pressure were conducted in seawater for a glass flake epoxy coating. Electrochemical impedance spectroscopy (EIS) was used to characterize the degradation processes of the coating during the tests, and the surface of the coating was analyzed using an optical microscope, scanning electron microscope (SEM), and a Fourier transform infrared spectrometer (FTIR). The results showed that periodic cathodic polarization coupled with high hydrostatic pressure can accelerate the degradation of a coating by facilitating the diffusion and uptake of electrolyte and the delamination of the coating. The coupled test method has the largest acceleration due to the synergetic effect of AC-DC-AC and hydrostatic pressure. Full article

This paper presents a detailed study of a titanium–platinum thin film-based electrode preparation and its practical application in the electrooxidation of cyanides to help protect our environment. The novel electrochemical deposition process of Pt on nearly atomically smooth magnetron-sputtered Ti film has been used to prepare a highly effective glass|Ti|Pt composite electrode with high catalytic activity for the electrooxidation of cyanide ions. The composite electrode exhibits over a 90% electrical current efficiency in the cyanide electrooxidation process and can be used for the decontamination of highly concentrated KCN solutions (up to 0.1 M) without any chemical additives. A high current efficiency (70%) of Pt thin film deposition on a glass|Ti electrode was achieved using a potentiostatic double-pulse method. Fast Fourier transform electrochemical impedance spectroscopy revealed the oxidation kinetics for cyanide ions at the electrode. The glass|Ti electrode was prepared using the magnetron sputtering technique, which allows us to fabricate electrodes of any shape suitable for any electrochemical cell or electroplating bath. Meanwhile, electrochemical deposition of Pt on the glass|Ti electrode is an efficient and environmentally friendly method, since various salts of Pt and/or Pt-containing wastes can be used for electrodeposition instead of pure Pt, which is more expensive. Full article

This paper presents a detailed study of a novel type of electrochemical mercury ion (Hg²⁺) biosensor developed by combining Prussian blue (PB) and catalase (Cat). The simultaneous PB-catalyzed reduction of hydrogen peroxide and the inhibition of catalase by Hg²⁺ ions were used as the working principle of the biosensor. The biosensor described in this research was capable of detecting Hg²⁺ ions at relatively low potentials (+0.2 V vs. Ag|AgCl, KCl_sat) using chronoamperometry and a fast Fourier transform electrochemical impedance spectroscopy (FFT-EIS). Linear ranges of 0.07 mM–3 mM and 0.13 mM–0.80 mM of Hg²⁺ ions were obtained using amperometric and impedimetric techniques, respectively. In the course of this work, an amperometric study of the Hg²⁺ ion biosensor was also carried out on a real sample (tap water containing Hg²⁺ ions). Full article

Bismuth vanadate (BiVO₄, BV) is a widely explored photocatalyst for photo(electro)chemical applications, but its full photocatalytic potential is hindered by the fast recombination and low mobility of photogenerated charge carriers. Herein, we propose the photodeposition of different amounts of Prussian blue (PB) cocatalysts on the surface of monoclinic BV to obtain BV-PB composite photocatalysts with increased photoactivity. The as-prepared BV and BV-PB composites were characterized by an array of analytic techniques such scanning eletron microscopy (SEM), transmission eletron microscopy (TEM), X-day diffraction (XRD), and spectroscopic techniques including Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and Raman spectroscopy. The addition of PB not only increases the absorption of visible light, as indicated by DRS, but also improves the charge carriers’ transfer across the photocatalysts/solution interface and hence reduces electron-hole (e⁻-h⁺) recombination, as confirmed by EIS and PL measurements. Resultantly, the BV-PB composite photocatalysts with optimum PB loading exhibited enhanced Cr(VI) photoreduction efficiency as compared to pristine BV under visible light illumination from low-power blue light-emitting diodes (LEDs), thanks to the cocatalyst role of PB which mediates the transfer of photoexcited conduction band (CB) electrons from BV to Cr(VI) species in solution. Moreover, as compared to pristine BV and BV + H₂O₂, a drastic increase in the methylene blue (MB) photo-oxidation efficiency was observed for BV-PB in the presence of a minute quantity of H₂O₂ due to a synergic effect between the photocatalytic and Fenton-like processes. While pure BV photodegraded around 70% of MB dye within 120 min, the BV-PB/H₂O₂ and BV/H₂O₂ system could degrade almost 100% of the dye within 20 min (k_obs. = 0.375 min⁻¹) and 40 min (k_obs. = 0.055 min⁻¹), respectively. The practical approach employed in this work may pioneer new prospects for synthesizing new BV-based photocatalytic systems with low production costs and high photoredox efficiencies. Full article

Electrochemical impedance spectroscopy (EIS) is a well-established method of battery analysis, where the response of a battery to either a voltage or current excitation signal spanning a wide frequency spectrum is measured and analyzed. State-of-the-art EIS analysis is limited to high-precision measurement systems within laboratory environments. In order to be relevant in practical applications, EIS analysis needs to be carried out with low-cost sensors, which suffer from high levels of measurement noise. This article presents an approach to estimate the equivalent circuit model (ECM) parameters of a Li-Ion battery pack based on EIS measurements in the presence of high levels of noise. The proposed algorithm consists of a fast Fourier transform, feature extraction, curve fitting, and least-squares estimation. The results of the proposed parameter-estimation algorithm are compared to that of recent work for objective performance comparison. The error analysis of the proposed approach, in comparison to the existing approach, demonstrated significant improvement in parameter estimation accuracy in low signal-to-noise ratio (SNR) regions. Results show that the proposed algorithm significantly outperforms the previous method under high-measurement-noise scenarios without requiring a significant increase in computational resources. Full article

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements. Full article

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH₂), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol–gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N₂ sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH₂ material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)₆]³⁻. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s⁻¹, indicating a fast direct electron transfer rate of [Fe(CN)₆]³⁻ to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb²⁺ ions on TalcNH₂/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10⁻⁸ M (S/N = 3) and 24.84 × 10⁻⁸ M (S/N 10), for the determination of Pb²⁺ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb²⁺ ions by the grafted NH₂ groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors. Full article

The development of a sensitive glucose monitoring system is highly important to protect human lives as high blood-glucose level-related diseases continue to rise globally. In this study, a glucose sensor based on polyaniline-bimetallic oxide (PANI-MnBaO₂) was reported. PANI-MnBaO₂ was electrochemically synthesized on the glassy carbon electrode (GCE) surface. The as-prepared PANI-MnBaO₂ was characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Glucose sensing on PANI-MnBaO₂ is based on the electrocatalytic oxidation of glucose to the glucolactone, which gives oxidation current. The oxidation potential for glucose was 0.83 V, with a limit of detection of 0.06 µM in the linear and in the concentration range of 0.05 µM–1.6 mM. The generated current densities displayed excellent stability in terms of repeatability and reproducibility with fast response. The development of a sensitive glucose sensor as obtained in the current study would ensure human health safety and protection through timely and accurate glucose detection and monitoring. Full article

Simple carbohydrates are associated with the enhanced risk of cardiovascular disease and adverse changes in lipoproteins in the organism. Conversely, sugars are known to exert a stabilizing effect on biological membranes, and this effect is widely exploited in medicine and industry for cryopreservation of tissues and materials. In view of elucidating molecular mechanisms involved in the interaction of mono- and disaccharides with biomimetic lipid systems, we study the alteration of dielectric properties, the degree of hydration, and the rotational order parameter and dipole potential of lipid bilayers in the presence of sugars. Frequency-dependent deformation of cell-size unilamellar lipid vesicles in alternating electric fields and fast Fourier transform electrochemical impedance spectroscopy are applied to measure the specific capacitance of phosphatidylcholine lipid bilayers in sucrose, glucose and fructose aqueous solutions. Alteration of membrane specific capacitance is reported in sucrose solutions, while preservation of membrane dielectric properties is established in the presence of glucose and fructose. We address the effect of sugars on the hydration and the rotational order parameter for 1-palmitoyl-2-oleoyl-sn-glycero-3- phosphocholine (POPC) and 1-stearoyl-2-oleoyl-sn-glycero-3- phosphocholine (SOPC). An increased degree of lipid packing is reported in sucrose solutions. The obtained results provide evidence that some small carbohydrates are able to change membrane dielectric properties, structure, and order related to membrane homeostasis. The reported data are also relevant to future developments based on the response of lipid bilayers to external physical stimuli such as electric fields and temperature changes. Full article

By simple modification of a GC electrode with biofunctional material, hydroxyapatite (HAp), an efficient electroanalytical tool, was designed and constructed. Modification of the GC surface includes two steps in synthesis: electrochemical deposition and chemical conversion. The properties, structure, and morphology of a nanosized material formed on a surface and absorbability were studied by electrochemical impedance spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy with energy-dispersive spectroscopy analysis. Numerous methods in this work confirmed that the developed method for controlled HAp deposition results in a HAp open structure and uniform morphology, which is capable of the selective absorption of the target species. The main goal of this study was the possibility of using a HAp-modified electrode for the fast screening of copper, cadmium, and lead content in honey and sugar samples. The electrochemical behavior and potential of the electroanalytical determination of heavy metals using the HAp/GC electrode were studied using cyclic voltammetry and square wave anodic stripping voltammetry. The HAp/GC electrode exhibited great performance in the determination of heavy metals, based on the reduction of target metals, because of the high absorbability of the HAp film and the electroanalytical properties of GC. A linear response between 10 and 1000 μg/L for Cu and Pb and 1 and 100 μg/L for Cd, with an estimated detection limit of 2.0, 10.0, and 0.9 μg/L, respectively, was obtained. Full article

In this work, a novel nanocomposite consisting of electrosynthesized gold nanodendrites and chitosan nanoparticles (AuNDs/CSNPs) has been prepared to fabricate an impedimetric immunosensor based on a screen printed carbon electrode (SPCE) for the rapid and sensitive immunoassay of botulinum neurotoxin A (BoNT/A). BoNT/A polyclonal antibody was immobilized on the nanocomposite-modified SPCE for the signal amplification. The structure of the prepared nanocomposite was investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The charge transfer resistance (R_CT) changes were used to detect BoNT/A as the specific immuno-interactions at the immunosensor surface that efficiently limited the electron transfer of Fe(CN)₆^3−/4− as a redox probe at pH = 7.4. A linear relationship was observed between the %∆R_CT and the concentration logarithm of BoNT/A within the range of 0.2 to 230 pg·mL⁻¹ with a detection limit (S/N = 3) of 0.15 pg·mL⁻¹. The practical applicability of the proposed sensor was examined by evaluating the detection of BoNT/A in milk and serum samples with satisfactory recoveries. Therefore, the prepared immunosensor holds great promise for the fast, simple and sensitive detection of BoNT/A in various real samples. Full article