Impedance Spectroscopy Methods Research Articles

Impedance Spectroscopy as a Powerful Tool for Researching Molybdenum-Based Materials with Schiff Base Hydrazones.

Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum Schiff base complexes were prepared via the reaction of [MoO2(acac)2] with a hydrazone Schiff-base tetradentate ligand. A new hydrazone-Schiff base (H2L1 and 2) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H2L2 ligands and the complexes [MoO2(L1)(H2O)], [MoO2(L2)(H2O)], [MoO2(L1)(MeOH)]∙MeOH, [MoO2(L1)(EtOH)]∙EtOH, [MoO2(L1)(2-PrOH)]∙2-PrOH, and [MoO2(L1)]n were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.

Vinylene carbonate, toluene and diethyl ether as electrolyte additives for a wide-temperature range operating of EDLCs

This work presents the development of an electrolyte solution based on 1.2 M TEMA BF4 AN:EA (3:1) electrolyte mixture modified with diethyl ether (5–20 vol%), or toluene (5–20 vol%), or vinylene carbonate (0.5–5 vol%) ensuring stable operation of the supercapacitors (SC) in a wide temperature range from −68 °C to +60 °C. Supercapacitor cells with electrolytes of various volume ratios of components were investigated using cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy (EIS) methods. Specific conductivity values have been measured and compared with electrochemical impedance data. It was shown that the additives to the base electrolyte blend expand the operating temperature range of the SC cells by at least 7–8°, enabling its exploitation at lower temperatures (−68 °C). It has been established that the addition of 10 vol% of diethyl ether or toluene stabilizes the operation of the SC at −65 °C, demonstrating stability during long-term exposure. Vinylene carbonate additive most effectively stabilizes the work of the SC at high temperatures (+60 °C). Diethyl ether as an additive effectively promotes the operation of SC only at low temperatures (−68 °C), while at high temperatures, it leads to the degradation of SC.

Conductivity, its anisotropy and changes as a manifestation of the features of the atomic and real structures of superprotonic [K1-x(NH4)x]3H(SO4)2 crystals.

Single crystals of [K1-x(NH4)x]3H(SO4)2 (x ≥ 0.57) grown in the K3H(SO4)2-(NH4)3H(SO4)2-H2O water-salt system are studied. The atomic structure including H atoms was determined at room temperature using X-ray structural analysis. [K1-x(NH4)x]3H(SO4)2 (x ≥ 0.57) crystals have trigonal symmetry and disordered hydrogen-bond networks at ambient conditions similar to the high-temperature phases of K3H(SO4)2, (NH4)3H(SO4)2 and other superprotonic compounds M3H(AO4)2. Impedance measurements performed on single crystals show high values of conductivity characteristic for superprotonic phases. Using the methods of impedance spectroscopy and atomic force microscopy, a significant anisotropy of the conductivity of crystals has been detected. It was also shown that there is a qualitative correlation of bulk and local conductivity measured for samples of the same composition and orientation at room temperature, which is due to the peculiarities of their crystal structure.

Effect of Bacillus and Pseudomonas biofilms on the corrosion behavior of AISI 304 stainless steel

Abstract In this research work, the corrosion tendency of stainless steel 304 caused by the Pseudomonas aeruginosa ZK and Bacillus subtilis S1X bacterial strains is investigated. The topographical features of the biofilms achieved after 14 days of incubation at 37 °C were examined by means of scanning electron microscopy. Fourier transform infrared spectroscopic analysis of the extracellular polymeric substance was carried out to estimate the chemical composition of the biofilm. Electrochemical impedance spectroscopy and Tafel polarization test methods were applied to understand the in-situ corrosion tendency of the stainless steel 304 in the presence of P. aeruginosa ZK and B. subtilis S1X strains. Compared to the biofilm produced by the P. aeruginosa ZK, the extracellular polymeric substance in the B. subtilis S1X containing bacteria was found to be porous and non-uniform. The improved hydrophobicity and uniformity of the P. aeruginosa ZK containing biofilm retarded the corrosion of the underlying stainless steel 304 sample. Appreciably large resistance of the P. aeruginosa ZK biofilm (∼6.04 kΩ-cm2) and hindered charge transport (11.12 kΩ-cm2) were evident from the electrochemical impedance spectroscopy analysis. In support of these results, a large cathodic Tafel slope (0.2 V/decade) and low corrosion rate (1.69 μA cm−2) were corroborated by the inhibitive properties of the P. aeruginosa ZK containing biofilm. However, the localized corrosion of the substrate in the presence of B. subtilis S1X bacteria was caused by the porosity and non-homogeneity of the extracellular polymeric substance layer. The small charge transfer resistance, high dissolution rate and pitting of the surface under B. subtilis S1X biofilm were comparable to the corrosion properties of stainless steel 304 in a controlled medium. These results highlighted the poor corrosion inhibitive properties of the B. subtilis S1X biofilm compared to the P. aeruginosa ZK bacterial strain.

Effects of copper substitution on the structural, electrical, and magnetic properties of zinc and lanthanum (Zn1−xCuxLa0.1Fe1·9O4) nanoferrites

Zn1−xCuxLa0.1Fe1·9O4 (x = 0.09, 0.18, 0.27, and 0.36) nanoferrites were indigenously prepared by the sonochemical approach and examined using X-ray diffraction (XRD) and electrochemical impedance spectroscopy methods, and a Foner magnetometer. The XRD studies confirmed the cubic-spinel arrangement in the prepared Zn1−xCuxLa0.1Fe1·9O4 samples with a median crystallite size of 55, 48, 41, and 34 nm for x = 0.09, 0.18, 0.27, and 0.36, respectively, using the Scherrer's equation. The Nyquist impedance plots showed that the nanoferrite samples had resistive and pseudocapacitive behavior. In the vibrating-sample magnetometry studies, elevation in saturation magnetization and depreciation in coercivity was conducted while increasing the Cu2+ content, which highlighted the ferromagnetic behavior of the nanoferrites. Further, addition of copper in Zn1−xCuxLa0.1Fe1·9O4 nanoferrites enhanced the magnetic and electrical characteristics, which are discussed briefly.

Insight on Corrosion Prevention of C1018 in 1.0 M Hydrochloric Acid Using Liquid Smoke of Rice Husk Ash: Electrochemical, Surface Analysis, and Deep Learning Studies

This work reports the anti-corrosion behavior of liquid smoke from rice husk ash to unveil the contribution of its active compounds in 1 M HCl solution. In this study, the developed methodology to test, analyze, and model the novel type of green corrosion inhibitor for C1018 was characterized using Electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization, and deep learning methods. The inhibitor structure was characterized by Fourier transform infrared analysis (FTIR) and Ultraviolet–visible spectroscopy (UV-Vis). The surface characterization of mild steel immersed in blank and 80 ppm solution inhibitor was performed using Atomic force microscopy (AFM) analysis. The corrosion test results show that the inhibitor is considered a mixed-type inhibitor to achieve the optimum inhibition of 80 ppm at 323 K, reaching up to 99% inhibition efficiency. The AFM results show a smoother surface given a lower skewness parameter at −0.5190 nm on the treated mild steel. The artificial neural network demonstrates the lower overfitting on the inhibited steel, a higher accuracy prediction of 81.08%, and a lower loss rate of 0.6001 to model the relationship between the EIS and Potentiodynamic polarization and the evolution of the passive layer on the treated mild steel. The experiment agrees well with the prediction result to model the adsorbed inhibitor. The work can be used as a guideline to pave the way for subsequent applicability in developing green corrosion inhibitors based on experimental and artificial intelligence approaches.

Corrosion behavior of AlCoCrFeNix high entropy alloys

In this study, the effects of three different nickel concentrations on the microstructure, hardness, and corrosion properties of AlCrFeCoNix (x = 1.0, 1.5, 2.0) high entropy alloys (HEA) were investigated. The alloys were obtained by arc melting from high-purity raw materials and subjected to heat treatment at 1125 °C for 5 h. Microstructural characterization revealed a dendritic morphology for the equimolar and AlCrFeCoNi1.5 alloys, while the AlCrFeCoNi2 alloy presented a hypoeutectic microstructure. Differences in microstructure and chemical composition were observed between the dendritic and interdendritic regions, with clear segregation of Cr in the interdendritic areas. The increase in Ni content and the heat treatment resulted in the formation of the FCC phase, consequently reducing the alloys' hardness. The corrosion properties of HEA were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy methods in a 3.5% NaCl solution. The results show high resistance to localized corrosion of the alloys, evidenced by the low values of corrosion current densities, and high pitting potentials. The protective film's formation depends on Ni content, which is also related to FCC/BCC ratio and phase compositions. The heat treatment generally results in a more homogeneous, thicker, and less defective oxide film.

Proton Conductivity in Rare-Earth Fluorine-Containing Molybdates NaLn4Mo3O15F

The fluorine-containing fluorite-like compounds of composition NaLn4Mo3O15F (Ln = La, Pr, Nd) are produced using the method of solid-phase synthesis in air. Their thermomechanical and conducting properties, as well as hygroscopicity, are studied. It is confirmed that the synthesized specimens are isostructural to the cubic compounds Ln5Mo3O16 with the fluorite-like structure. It is shown that in the temperature range of 20–600°C, the specimens of NaLn4Mo3O15F (Ln = La, Pr, Nd) expand linearly, and their thermal expansion coefficients (13–14) × 10–6 K–1 are close to the coefficients of conventional SOFC electrolytes, for example, YSZ. Using the thermal gravimetric analysis, it is shown that the weight loss of the studied specimens in the range from 30 to 700°C is caused by their hygroscopicity. The electrophysical properties of the compounds are studied using the method of impedance spectroscopy in the humid atmosphere, and the proton component of conductivity is revealed.

Measuring temperature dependence of dimensionless figure of merit of a thermoelectric module using time-domain impedance spectroscopy.

This paper introduces transient Harman (TH), impedance spectroscopy (IS), and time-domain impedance spectroscopy (TDIS) methods as feasible techniques for determining the temperature dependence shown by the dimensionless figure of merit (zT) of a BiTe-based thermoelectric module from 50 to 320K. An optimum current was selected to deduce the proper zT under a dominant Peltier heat. The comparison results indicated that the TH method enables a rapid estimation of zT, typically within several minutes. Although the measurement times for the IS (several minutes to hours) and TDIS (several minutes) methods were different, both the methods yielded comparable zT values, and the TDIS method was found to be more reliable for the module with zT > 0.02 and a resolution of 0.001. Furthermore, temperature stabilization of the measurement specimen using the TDIS method also emerged as one of the key factors that determined the accuracy and resolution of the zT estimation.

Development of highly selective and sensitive molecularly imprinted polymer-based electrochemical sensors for tolvaptan assay in tablets and serum.

In this research, two different molecularly imprinted polymer (MIP)-based electrochemical sensors were proposed for the determination of tolvaptan (TOL). Photopolymerization (PP) and thermal polymerization (TP) techniques were developed for the determination of TOL. The advantages of MIP were used to design an electrochemical sensor for selective and sensitive determination of TOL. TOL was determined on a glassy carbon electrode (GCE) using differential pulse voltammetry (DPV) for both techniques. Some important parameters affecting the sensor efficiency, such as template/monomer ratio, PP and TP time, drop volume, removal solutions, removal and rebinding time, etc., were optimized. The surface characterization of the proposed MIP-based electrochemical sensors was carried out with electrochemical characterization by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. It was extended with the scanning electron microscopy (SEM) technique. Under optimal conditions, the developed sensors showed good linearity between 1.0 × 10-11 M and 1.0 × 10-10 M, and 2.5 × 10-11 M and 2.5 × 10-10 M for PP and TP, respectively. Low detection limits (2.89 × 10-12 M (PP) and 1.88 × 10-13 M (TP)) were also obtained for TOL determination. The applicability of the proposed sensor was evaluated using tablet and commercial human serum samples. Interference and imprinting factor studies verified the selectivity and specificity of the proposed sensors, and the efficiency of the sensors was verified using an unprinted polymer for comparison at each step.

Comparison of electrochemical corrosion performance of eutectic Al-Si automotive alloy in deep seawater and 3.5% NaCl solution

The corrosion of aluminium silicon alloys is of vital importance, as they are frequently exposed to corrosive environments. The alloy is often exposed to seawater in marine applications, and despite having NaCl, the seawater contains some other ions. The purpose of this study is to compare the electrochemical corrosion performance of eutectic Al-Si alloys in seawater with 3.5% NaCl in order to understand the effects of those additional components, and an alloy with trace silicon is also considered for comparison. Electrochemical impedance spectroscopy (EIS) and Tafel polarization methods were implemented for the corrosion analysis. The results of these methods imply that the eutectic alloy is more resistant to corrosion in seawater than in NaCl solution. Some additional elements in seawater produce protective layers on the alloy surface, shielding the alloy from corrosion in seawater. The open circuit potential is shifted towards the nobler direction for the eutectic alloy than in the trace Si-added alloy. The eutectic alloy's corrosion rate and current (Icorr) are higher. Mg2Si precipitates in the eutectic alloy, forming oxide films of MgO and SiO2, protect the alloy from further corrosion. The alloys' surface morphologies were analyzed not only by optical microscope but also by scanning electron microscope. The photos depict reduced damage on the surfaces corroded in the seawater environment compared to the NaCl solution environment. The Si phases are discernable in these images. Additional demolishment and pit formations are identified on the surfaces of the eutectic alloy from SEM inspection. Fewer pits and damages are observed in the case of seawater environments. The EDS analysis shows a higher amount of oxygen for the alloy corroded in NaCl solution, supporting the phenomenon of more damage than in seawater.

Implementation of the impedance spectroscopy using a modern microcontroller

Impedance spectroscopy is a widely used analytical method in the material sciences that is used to study transport processes, the rate and properties of chemical reactions, corrosion, dielectric properties, microstructures and electrical conductivity in solids. The subject of the paper is a description of the possibilities of implementation the impedance spectroscopy method on the chip of a modern universal microcontroller with a minimum of external components using integrated microcontroller peripherals with the possibility of measuring material characteristics in the frequency range from 0.1 Hz to 300 kHz.The implementation on the ARM STM32L476 microcontroller chip is given as an example of miniaturization the presented concept intended for measuring material characteristics in-situ.

ONE-STEP ELECTROCHEMICAL SYNTHESIS OF PEDOT BASED COMPOSITES FOR SUPERCAPACITOR APPLICATIONS

The aim of this work was to determine the optimal synthesis conditions for the preparation of a poly(3,4-ethylenedioxythiophene) (PEDOT) layer by the electrochemical method from an electrolyte containing graphene oxide (GO) and a sodium dodecylsulfate (SDS) micellar solution. Besides an SDS anion, GO is also incorporated within the PEDOT layer as a negative counter ion. Therefore, this is a one-step electrochemical method for a PEDOT/GO composite layer preparation. The results displayed that PEDOT composites were successfully synthesised by applying a potential in the value range from 0.94 to 1.00 V, and with a synthesis duration of up to 600 s. It was concluded that the optimal concentration of EDOT monomer is 0.02 mol dm-3, and SDS 0.01 mol dm-3. The incorporation of GO into the PEDOT layer improved the polymer response in KCl solution influencing the pseudocapacitive properties, which is significant for its supercapacitor applications. The morphological and structural properties of the obtained layers were characterized by means of scanning electron microscopy and ultraviolet-visible spectrophotometry. The pseudocapacitive properties were determined in a 0.1 mol dm-3 KCl solution by using cyclic voltammetry and electrochemical impedance spectroscopy methods.

Yeni Tür Yeşil Korozyon İnhibitörü Olarak Citrus aurantium Meyve Kabukları Ekstraktının HCl Çözeltisindeki Yumuşak Çelik Korozyonu Üzerine Kararlı Etkisi

The role of Citrus aurantium fruit peel extract solution in the existing research is to investigate the effect as corrosion inhibitor on mild steel in the atmospheric environment with its eco-friendly and green effect. It was studied the inhibitor effect of Citrus aurantium utilizing linear polarization (LPR), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The working electrodes were immersed in HCl solutions containing various concentrations of Citrus aurantium fruit peels extract in order to equilibrate the metal-solution interface for one hour before each measurement. The bitter orange fruit peels extract indicated a potent inhibitor influence as a consequence of one hour electrochemical tests, and with the raise of extract concentrations of Citrus aurantium fruit peels, the protection influence of mild steel electrodes in HCl solutions also enhanced. Finally, the surface morphologies of the working electrodes in aggressive HCl solutions without and with bitter orange fruit peels extract after one-hour immersion were analysed by an optical microscopy, it was concluded that the mild steel surface in the Citrus aurantium fruit peels extract solution had a flawless surface compared to the blank one. Experimental data and surface morphology results are highly consistent with each other.

Machine Learning Approach to Classify Breast Tissues: A Case Study Using Six-classed Breast Tissue Data

The present study investigates the effectiveness of six Machine Learning (ML) algorithms in classifying the breast tissue dataset generated using the electrical impedance spectroscopy method. This study used the breast tissue dataset available at the UCI machine learning repository, consisting of 106 spectral records with ten variables. The data were partitioned into train and test datasets. Sixty six percentage of data was allocated for the train dataset and balance for the test dataset. Six ML algorithms were tested for effectiveness using accuracy, Cohen’s Kappa, sensitivity and specificity. The results revealed that the backpropagation algorithm (BPN) produced the highest accuracy and Kappa compared to other machine learning algorithms in classifying the six-classed breast tissue dataset. Both Support Vector Machine (SVM) and K-Nearest Neighbors (KNN) produced the second-highest accuracy and Kappa. The C5.0 decision tree algorithm takes the third level. The fourth and fifth levels of accuracy are Probabilistic Neural Network (PNN) and Learning Vector Quantization (LVQ), respectively. The sensitivity of all classes by the classification of BPN was more than eighty percentage, which is higher than other machine learning algorithms. The specificity of all classes predicted by BPN was more than ninety six percentage and was comparatively at the highest level than other machine learning algorithms. Therefore, the study concludes that the backpropagation algorithm will effectively classify the six classed breast tissue data.

Comparative Analysis of a New Class of Symmetric and Asymmetric Supercapacitors Constructed on the Basis of ITO Collectors

The paper presents the results of research on new electroconductive polymer materials, based on polypyrrole, for the different supercapacitor constructions, i.e., the symmetric and asymmetric constructions. All the supercapacitors considered contain ITO collectors. Measurements of the complex impedance frequency characteristics were performed for these elements using the electrochemical impedance spectroscopy (EIS) method. Selected fractional-order models, known from the literature, have been used to model the impedance of these elements. The Particle Swarm Optimization (PSO) algorithm was used to estimate the model parameters. Selected estimation results, their comparison, and conclusions are also presented in the paper. The type of active electrolyte component has the greatest impact on the shape of the impedance frequency characteristics. In most cases, the highest capacitance values and the smallest resistance values were obtained for asymmetric supercapacitors.

Preparation of intelligent corrosion resistant coatings based on pH-responsive silica nanocontainers

This work introduces the synthesis of smart silica nanoparticles loaded with a corrosion inhibitor (2-mercaptobenzothiazole) and embedded in composite organosilane coatings for corrosion protection of carbon steel. Through the BET test, the results show that the mechanically stabilized silica nanoparticles have the characteristics of large specific surface area, narrow pore size distribution and large pore volume. This also provides conditions for sufficient loading of the corrosion inhibitor (CI). Further, smart nano-containers are prepared by encapsulating CI in a layer-by-layer (LBL) self-assembly manner. The anticorrosion properties of the coatings were investigated by electrochemical impedance spectroscopy (EIS) and polarization curve characterization methods. The results indicate that the addition of smart silica nanoparticles can improve the corrosion resistance of the coating. This method simplifies the synthesis process of nanocontainers, which will be widely used in the fabrication of novel nanocontainers and opens up new prospects for active anticorrosion.

Stainless Steel Foil-Based Label-Free Modular Thin-Film Electrochemical Detector for Solvent Identification.

Most organic solvents are colorless liquids, usually stored in sealed containers. In many cases, their identification depends on the appropriate description on the container to prevent mishandling or mixing with other materials. Although modern laboratories rely heavily on identification technologies, such as digitized inventories and spectroscopic methods (e.g., NMR or FTIR), there may be situations where these cannot be used due to technical failure, lack of equipment, or time. An example of a portable and cost-effective solution to this problem is an electrochemical sensor. However, these are often limited to electrochemical impedance spectroscopy (EIS) or voltammetry methods. To address this problem, we present a novel modular electrochemical sensor for solvent identification that can be used with either an EIS-enabled potentiostat/galvanostat or a simple multimeter. A novel method of fabricating and using a sensor consisting of a thin-film coating of an organic substance on a stainless-steel electrode substrate is presented. The differences in the solubility of the thin film in different solvents are used to distinguish between common organic solvents such as water, ethanol, and tetrahydrofuran.

Modification of Carbon Nanomaterials by Association with Poly(3-octylthiophene-2,5-diyl) as a Method of Improving the Solid-Contact Layer in Ion-Selective Electrodes.

A new group of carbon nanomaterials modified with poly(3-octylthiophene-2,5-diyl) for solid-contact layers in ion-selective electrodes was obtained. The materials were characterized by scanning electron microscopy and measurement of the contact angle. The modification greatly improved the hydrophobicity of the materials, and the highest contact angle (175°) was obtained for a polymer-modified carbon nanofibers/nanotube nanocomposite. The electrical parameters of the electrodes were determined using the methods of chronopotentiometry and electrochemical impedance spectroscopy. The highest electrical charge capacity was obtained for polymer-modified carbon nanofibers (7.87 mF/cm2). For this material, the lowest detection limit (10-6.2 M) and the best potential reversibility (SD = 0.2 mV) were also obtained in potentiometric measurements.

The effect of silver nanoparticles on the structure and functional properties of antimicrobial polymer nanocomposites based on polyethylene oxide

The presence of antibacterial materials in biomedicine and related fields of science and technology has become essential. Excellent antibacterial activity and low cytotoxic potential of silver nanoparticles generally depend not only on their size, but also on the distribution in matrix media. The development of stabilized polymer-silver nanocomposites containing nanoparticles is considered to be one of the most promising solutions. We developed a new approach to the synthesis of silver nanoparticles. The structure and properties of antimicrobial nanocomposite materials based on polyethylene oxide and synthesized silver particles were studied using the methods of electron microscopy, differential scanning calorimetry, impedance spectroscopy and disk-diffusion microbiological method. As a result, silver nanoparticles with an average size of about 8-10 nm were obtained. It was established that stabilized silver nanoparticles significantly affect the thermophysical and electrical properties of the polymer matrix at relatively low concentrations of the nanofiller (1-2%). The total electrical conductivity of the systems increases by two orders of magnitude when 2% filler is added. Nanocomposite material containing 2% of silver nanoparticles shows significant activity against Staphylococcus aureus (inhibition zone 22 mm). The novel aproach for synthesis of stabilized silver nanoparticles open a new window of possibilities in the development of new antimicrobial materials, based on various polymer matrix: from thermoplastic to elastic. The developed materials with improved functional characteristics in the future can be used as antimicrobial coatings, antimicrobial films and creams, as well as construction products with the necessary functional characteristics and antimicrobial function.