Electrochemical Impedance Spectroscopy Research Articles

Oxygen evolution reaction of tellurium-incorporated nickel-iron layered double hydroxide microcrystals

Transition-metal-based layered double hydroxide (LDH) crystals have generated substantial interest as highly efficient oxygen evolution reaction (OER) catalysts because of their abundance, low cost, environmental friendliness, and favourable adsorption/desorption energies for intermittent reactants. However, the application of LDH crystals as high-performance electrocatalysts is frequently hindered by their sluggish electronic transport kinetics resulting from their intrinsically low conductivity. Herein, we report the effects of incorporating metalloids into transition metal LDH crystals on their electrocatalytic activity. In this study, tellurium (Te) incorporated NiFe (xTe-NiFe) LDH microcrystal, where x = 0.2, 0.4, 0.6 and 0.8, were grown on three-dimensional porous nickel foam using a facile solvothermal method. The electrocatalytic OER properties were analyzed using linear sweep voltammetry and electrochemical impedance spectroscopy. The amount of Te was found to play a crucial role in improving the catalytic activity of NiFe LDH. The optimum amount of Te (x) introduced into NiFe LDH was examined with respect to the OER performance.

Development of transition metal oxide platforms for aptasensing of PSA in cell cultures.

In this study, a novel aptasensor based on a transition metal oxide-modified pencil graphite electrode (PGE) was developed for the diagnosis of early-stage prostate cancer (PCa) via monitoring the prostate-specific antigen (PSA), which is the main biomarker for PCa. Single-use PGEs modified with pulsed deposited manganese oxide (MnOx) film were used to attach the amino-terminated aptamer specific to the PSA via carbodiimide chemistry. The designed aptasensor was placed in an electrochemical cell containing ferri/ferrocyanide ions as a redox probe to measure the charge transfer resistances (Rct) of the electrode surface by electrochemical impedance spectroscopy (EIS) to follow the response of each modification step. The effect of the medium pH on the ionic structure of the aptamer molecule according to its pI value and, thus, the reversing of the direction of the response (ΔRct) by the pH change was also discussed. The level of PSA secreted from PCa cells was investigated using impedimetric transduction. The specificity of the aptasensor was validated through selectivity studies against non-specific tumor markers like VEGF and different cancer cell lines including breast cancer and androgen-insensitive prostate cancer. The developed system showcases a label-free, fast, specific, and cost-effective approach for PSA detection, highlighting the importance of medium pH and the electrostatic environment on the aptamer's response. Our work emphasizes the potential for such aptasensors in clinical diagnostics and paves the way for further exploration into using transition metal oxides in biosensing applications.

Dissociative electrochemical analysis of materials degradation of an anion exchange membrane electrolyser

For anion exchange membrane (AEM) electrolysers, degradation studies provide valuable insights into how individual components degrade. Often, this presents a formidable challenge as each component significantly contributes to overall degradation. Here, we propose a methodology to individually compare the degradation of key components in AEM electrolysers: hydrogen evolution reaction (HER) catalyst, oxygen evolution reaction (OER) catalyst, and the AEM itself. First, to measure the degradation of catalyst-coated substrates (CCS) commonly used in AEM electrolysers, the AEM was replaced with a diaphragm (Zirfon Agfa UTP 500) permeable to OH− ions and stable in alkaline media. Subsequently, a cell with a stable catalytic layer (Nafion-coated Ni-felt substrates) was assembled to focus on membrane degradation with an AEM Sustainion X37-50 Grade 60. Chronopotentiometry and electrochemical impedance spectroscopy (EIS) revealed that the cell with the AEM experienced a threefold increase in ohmic resistance, attributed to the loss of functional groups. Additionally, an ion exchange capacity (IEC) analysis indicated that Sustainion lost approximately 20% of its ion exchange capacity. In contrast, the cell composed of CCS and Zirfon showed lower degradation. EIS data fitting demonstrated increased kinetic-related resistances while the ohmic resistance remained unchanged. This work presents a practical approach for comparing component degradation in AEM electrolysers.

Charged Microdroplets Deposition for Nanostructured-Based Electrode Surface Modification

Accelerated synthesis of gold nanoparticles (AuNPs) in charged microdroplets produced by electrospray ionization (ESI) was exploited to modify the surface of graphite screen-printed electrodes (GSPEs). The deposited AuNPs were then functionalized by the charged microdroplets deposition of 6-ferrocenyl-hexanethiol (6Fc-ht) solutions that act as reducing and stabilizing agents and provide electrochemical properties for the modified electrodes. The morphology and composition of the AuNPs were characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrodes. The results showed that the ESI microdroplets deposition technique produces uniform and well-dispersed AuNPs on GSPE, and optimal conditions for deposition were identified, enhancing GSPE electrocatalytic performance. Further functionalization by ESI microdroplets of AuNPs with 6Fc-ht demonstrated improved redox properties compared with the conventional self-assembled monolayer (SAM) method, highlighting the technique’s potential for the easy and fast functionalization of electrochemical sensors.

Ag QDs modified BiOCl/UiO-66-NH2 Z-scheme heterojunction for accelerated visible light-driven photocatalytic degradation of ciprofloxacin

Ag quantum dots (QDs) anchored on the surface of BiOCl/UiO-66-NH2 Z-scheme heterojunctions were synthesized and characterized by various techniques such as X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), electrochemical impedance spectroscopy (EIS), and photoluminescence (PL). The effects of Ag QDs loading, pH values and co-existing anions on the photocatalytic performance were comprehensively analyzed. The results concluded that the Ag QDs modified catalysts exhibited excellent photocatalytic performance for the degradation of ciprofloxacin (CIP), especially, the catalyst with 5 % Ag QDs loading (referred to as ABU-5) achieved a degradation efficiency of 72 % within 120 min and the apparent reaction rate constant was 0.00538 min−1. The outstanding performance of the ABU-5 catalyst is attributed to the introduction of Ag QDs as electron transfer bridges, improving visible light absorption and enhancing charge transfer between BiOCl and UiO-66-NH2. Free radical trapping experiments and leaching tests were carried out to determine the contribution rates of reactive species to the degradation efficiency and the concentration of Ag+ in solution after the reaction. The possible degradation pathways of CIP by ABU-5 were investigated by gas chromatography-mass spectrometry (GC-MS).

Anticorrosive two-dimensional heterostructured nanocoatings self-assembled on steel with multiple desired merits

In this study, an economic and controllable Marangoni self-assembly approach is designed to prepare the heterostructured nanocoatings (8–28 nm) consisting of alternately stacked mosaic nanosheets of hexagonal boron nitride (h-BN) and graphene. The resulting 2D nanocoatings exhibit a combination of advantageous properties, such as prevention of interfacial reactions, robust interfacial binding, a labyrinthine barrier effect, inhibition of galvanic corrosion, and alleviation of internal stress. The protective property of graphene/h-BN heterostructured nanocoatings is studied through potentiodynamic polarization curves and electrochemical impedance spectroscopy, with the theoretical support of first-principles calculations. The corrosion current density of ≈28 nm-thick graphene/h-BN multilayer coated stainless steel is 1.82 × 10−8 A cm−2, which decreases by an order of magnitude compared to that of an uncoated one, meanwhile, the corrosion potential increases from −0.192 to 0.023 V (increase: ≈0.215 V). The enhancement of anticorrosion performance of heterostructured nanocoatings can be attributed to the labyrinth barrier effect associated with highly ordered horizontal arrangement, effective coverage of metal substrates by mosaic multilayers, and suppressed galvanic corrosion effect by insulating BNNS monolayers. This study can shed much light on the effective solution of many stubborn issues confronted by the development of anticorrosive 2D nanocoatings.

Enhancing mechanical and anti-corrosion properties in a L12 nanoprecipitates reinforced Fe35.4Ni24Cr21Co9Mo2Cu1.6Al3Ti4 multi-principal element alloy via tailoring grain size

A Fe35.4Ni24Cr21Co9Mo2Cu1.6Al3Ti4 multi-principal element alloy (MPEA) reinforced by L12 nanoprecipitates was fabricated with four different grain sizes (~19, ~50, ~127 and ~361 μm) to optimize mechanical and corrosion properties. All samples exhibit a similar microstructure, showing spherical L12 nanoprecipitates embedded in the FCC matrix at grain interiors, accompanied by a small fraction of plate-like L12 and B2-ordered phases at grain boundaries. As grain size decreases, both yield strength and ultimate tensile strength progressively increase, while ductility decreases. The sample with a grain size of ~50 μm demonstrates the most excellent combination of strength and ductility, displaying a yield strength of ~700MPa, an ultimate tensile strength of ~1130MPa, and a total elongation of ~29.4%. Concurrently, corrosion resistance in 3.5wt.% NaCl improves as grain size decreases from ~361 μm to ~50 μm, but notably deteriorates at ~19 μm. These results suggest that the L12 nanoprecipitates reinforced Fe35.4Ni24Cr21Co9Mo2Cu1.6Al3Ti4 MPEA with grain size of ~50 μm has achieved outstanding combination of mechanical and anti-corrosion properties. Precipitation strengthening and grain boundary strengthening are responsible for the enhanced mechanical properties in the studied samples. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) revealed that the passive film on the ~50 μm grain size sample is the thickest (3.09nm), composed primarily of Cr2O3 and Fe2O3, which acts as an effective barrier against Cl- penetration. In a word, tailoring grain size proves to be an effective means to achieve enhanced mechanical and anti-corrosion properties.

Diffusion mechanisms and corrosion resistance of nanostructured ZrN-Cu coating obtained by hybrid HiPIMS-DCMS

Globalisation has brought numerous benefits regarding the cost-effective transportation of goods. Still, the shipping industry faces challenges such as corrosion, biofouling, and restrictions on heavy pollutant products used in paintings. This study proposes a solution using a multifunctional coating based on zirconium nitride and copper nano-structured coating, applying high-power impulse and direct current magnetron sputtering processes (i.e., HiPIMS and DCMS, respectively). The coating’s morphological, structural, and chemical features were analysed using advanced characterisation techniques (SEM, EDX, STEM, SAED and EELS). Potentiodynamic polarisation (PP) and Electrochemical Impedance Spectroscopy (EIS − up to 30 days) were employed to study the corrosion resistance in saline solution (3.5 wt% NaCl). Besides, activated ZrN-Cu exhibited a corrosion rate decrease from ∼ 354 x 10−4 to 52 x 10−4 mm/yr when compared to its inactivated counterpart. Besides, a ∼ 3.5-fold impedance increasing was exhibited by activated ZrN-Cu after 30 days of exposure to saline solution, meaning an increase in corrosion resistance compared to the non-activated ZrN-Cu. SEM micrographs revealed that the copper diffusion in ZrN-Cu can be provoked by a strong oxidising agent (NaOCl) or by an electrical potential. Based on the chartered evidence, a diffusion mechanism is proposed for the biocidal release (Cu) in the obtained ZrN-Cu films. The present study depicts a solution that offers a controlled biocide release and corrosion resistance, opening the possibility of its application in the maritime industry.

Synthesis, Characterization, Theoretical, and evaluation of Eco-Friendly benzimidazolylmethyl-pyrazole carboxylate Schiff Bases corrosion inhibitors for mild steel

In this study, benzimidazolylmethyl-pyrazole carboxylate derivatives were synthesized via a 1,3-dipolar cycloaddition reaction and characterized using IR, HRMS and NMR spectroscopy. Three derivatives, namely ethyl 5-((3-(cyclohex-1-en-1-yl)-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)methyl)-1-phenyl-1H-pyrazole-3-carboxylate (Ph-BPC), ethyl 5-((3-(cyclohex-1-en-1-yl)-2-oxo-2,3-dihydro- 1H-benzo[d]imidazol-1-yl)methyl)-1-(p-tolyl)-1H-pyrazole-3-carboxylate (CH3Ph-BPC), and ethyl 1-(4-chlorophenyl)-5-((3-(cyclohex-1-en-1-yl)-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)methyl)-1H-pyrazole-3-carboxylate (ClPh-BPC), were evaluated as corrosion inhibitors for mild steel (MS) in a 1 M HCl solution. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements revealed high inhibition efficiencies of 98.5 %, 98.2 %, and 97.7 % for ClPh-BPC, Ph-BPC, and CH3Ph-BPC, respectively, at a concentration of 10-4 M. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses confirmed the formation of protective surface layers, significantly reducing corrosion rates. Thermodynamic analysis indicated that the adsorption of these inhibitors follows the Langmuir isotherm model with adsorption energies of −50.12 kJ/mol for ClPh-BPC, −50.52 kJ/mol for Ph-BPC, and −51.62 kJ/mol for CH3Ph-BPC, suggesting chemisorption. Computational studies, including Monte Carlo (MC), density functional theory (DFT), and molecular dynamics (MD) simulations, showed strong agreement with experimental results, further validating the adsorption behavior and corrosion inhibition mechanisms of these compounds.

Effect of microstructural anisotropy and heat treatment on the corrosion behaviour of additively manufactured Ti-6Al-2Sn-4Zr-6Mo alloy

The electrochemical behaviour of Ti-6Al-2Sn-4Zr-6Mo alloy produced by Powder Bed Fusion – Laser Based/Metals has been investigated to identify the corrosion mechanism characteristic of the material processed by additive manufacturing technology. A microstructural characterisation of the material in as-built and heat-treated conditions was carried out to identify the different phases and assess the degree of anisotropy of the additive manufactured material. After that, the corrosion behaviour was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy. Results showed that a homogeneous and compact oxide layer characterises the as-built material due to the presence of a finely dispersed α’’ phase in the β grains. Conversely, in the heat-treated alloy, the corrosion attack proceeds preferentially on the large α phase domains, where the oxide layer is less protective. Despite the anisotropy in the microstructure of the as-built material, the electrochemical behaviour was revealed to be the same for the section parallel and perpendicular to the building direction, noting the less influential factor of grain orientation on corrosion mechanisms.

Electrochemical corrosion behavior and passive film properties of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy coating prepared by laser cladding

The phase composition, microstructure morphology, and corrosion behavior of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy (EHEA) coatings produced via laser cladding were investigated. The research delved into discerning the phase structures and microstructural variations of the EHEA coatings concerning differing Nb compositions. The findings highlighted a direct correlation between Nb content and the volume fraction of the eutectic structure, specifically the FCC/Laves phases. Electrochemical evaluations, including diverse tests such as potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization, Mott-Schottky measurements, and X-ray photoelectron spectroscopy, revealed distinct corrosion behaviors among the EHEA variants. Notably, the Fe2Ni2CrV0.5Nb0.2 coating exhibited relatively superior corrosion resistance compared with Fe2Ni2CrV0.5Nbx (x=0.4,0.6,0.8) coatings, attributed to its lower corrosion current density (Icorr) and the formation of a thicker passive film with prolonged passivation duration. Conversely, the Fe2Ni2CrV0.5Nb0.8 coating, characterized by increased eutectic structures and grain boundary density, yielded a thicker yet non-uniform passive film with higher vacancy defects. This comprehensive exploration into the corrosion behavior and passive film properties of these EHEA coatings provides a reference for designing materials that hold promising implications for future corrosion-resistant material development in industrial parts repair applications.

A highly sensitive and selective molecularly imprinted sensor for the determination of atorvastatin

In this study, we developed a highly sensitive carbon paste sensor that combines a molecularly imprinted polymer (MIP) with specific recognition capabilities to monitor atorvastatin (ATV). In the MIP synthesis, designed especially for ATV, ethylene glycol dimethacrylate (EGDMA) was utilized as a cross-linking monomer and methacrylic acid (MAA) as a functional monomer. This non-covalent method made use of polymerization by free radicals. After that, this MIP was added to a carbon paste electrode (CPE), which served as both a selective detection element and a preconcentration agent for ATV analysis. The improved CPE was characterized using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). To investigate ATV, the anodic peak signal was assessed using square wave stripping voltammetry (SWSV).The calibration curve exhibited two linear regions encompassing dosages from 0.005 to 1 µM and 1 to 20 µM, with a 1.5 nM calculated detection limit. The designed MIP electrode was successfully utilized to assess ATV in tablet and human blood serum samples, demonstrating its usefulness in practical analysis.

Spark plasma sintering of Ti2AlC/TiC MAX-phase based composite ceramic materials and study of their electrochemical characteristics

A novel method for obtaining the MAX phase Ti2AlC from TiC, Al4C3, and Ti precursors has been demonstrated, involving activation of the mixture in a high-energy ball mill (HEBM) followed by Spark Plasma Sintering (SPS). The phase composition, mechanical characteristics, surface microstructure, and electrochemical behavior in neutral media (0.1 M Na2SO4) of heterogeneous composite ceramic materials TiC/Ti2AlC were studied as a function of sintering temperature (1200–1400 °C). SPS at 1200 °C yields materials with a relative density of 94.42 % and Ti2AlC mass content up to 57 %. These composite materials exhibit capacitive behavior according to cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) data, with a capacitance of 73 mF/g, suggesting their potential application as lead-free ceramic capacitors. Further increase in sintering temperature (1300–1400 °C) leads to increased electrical resistance and enhanced sample homogeneity.

Optimized aptamer-based next generation biosensor for the ultra-sensitive determination of SARS-CoV-2 S1 protein in saliva samples

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which rapidly spread worldwide and resulted in a pandemic. Efficient and sensitive detection techniques have been devised since the onset of the epidemic and continue to be improved at present. Due to the crucial role of the SARS-CoV-2 S1 protein in facilitating the virus's entry into cells, efforts in detection and treatment have primarily centered upon this protein. In this study, a rapid, ultrasensitive, disposable, easy-to-use, cost-effective next generation biosensor based on optimized aptamer (Optimer, OPT) was developed by using a disposable pencil graphite electrode (PGE) and applied for the impedimetric determination of SARS-CoV-2 S1 protein. The S1 protein interacted with the OPT in the solution phase and then immobilized onto the PGE surface. Subsequently, measurements using electrochemical impedance spectroscopy (EIS) were conducted in a solution containing a redox probe of 1 mM [Fe(CN)6]3−/4−. Under optimum conditions, the limit of detection (LOD) for the S1 protein in buffer medium at concentrations ranging from 101 to 106 ag/mL was calculated as 8.80 ag/mL (0.11 aM). The selectivity of the developed biosensor was studied against MERS-CoV-S1 protein (MERS) and Influenza Hemagglutinin antigen (HA). Furthermore, the application of the biosensor in artificial saliva medium is demonstrated. The LOD was also calculated in artificial saliva medium in the concentration range of 101–105 ag/mL and calculated as 2.01 ag/mL (0.025 aM). This medium was also used to assess the selectivity of optimized-aptamer based biosensor.

Evaluation of the permeability of ultrathin parylene AF4 films to determine minimum closed thickness for nanoscale packaging

This study investigated the permeability of parylene AF4 films of varying thickness to determine the minimum closed thickness for nanoscale packaging coatings. In particular, films with thicknesses of 15, 20, and 25 nm were deposited using 1 g of dimer and by adjusting the coating machine’s chamber height. Closeness analysis and electrochemical impedance spectroscopy (EIS) were employed to determine the minimum closed thickness. The closeness analysis results revealed a resistance of 1.35 MΩ (below the 20 MΩ threshold) for the 15 nm film, indicating a nonclosed film; conversely, the 20 and 25 nm films exhibited resistance values of 66.1 and 111.7 MΩ (above the threshold), respectively, indicating closed films. The EIS results indicated that the failure soaking times of the 15, 20, and 25 nm films were approximately <10, 20, and 50 min, respectively. These results indicate that the 20 nm film exhibited the lowest minimum closed thickness and was effective for waterproofing. These findings contribute valuable data toward developing nanoscale waterproof coatings for packaging applications.

Bifunctional PAni@Bi/Ce metal organic framework-Chitosan composite for electrochemical sensing and energy storage applications

Tailoring pristine metal-organic frameworks (MOFs) offered a great opportunity in exploring electrochemical sensing and energy storage applications. This study presents a novel Polyaniline@Bi/Ce MOF-Chitosan composite synthesized via a solvothermal method and chemical oxidative polymerization. PXRD, FTIR, SEM, EDAX, and TEM characterization confirmed its structural and morphological properties. Electrochemical performance was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and electrochemical surface area (ECSA) analysis. The composite exhibited excellent electrocatalytic activity for detecting azithromycin and toluene with low detection limits and broad concentration ranges, demonstrated by voltammetry and amperometry. It showed significant stability for long term applications. Additionally, the material's energy storage capabilities were assessed through CV and galvanostatic charge-discharge (GCD) studies, revealing a specific capacitance of 415.32 F/g at 1.0 A g-1 and 90.48 % capacity retention after 5000 cycles at 6 A g-1. These findings highlight the Polyaniline@Bi/Ce MOF-Chitosan composite as a promising candidate for electrochemical sensing and energy storage applications.

Corrosion Inhibition of Tetrabutylphosphonium Benzotriazolate on Carbon Steel in Acidic Medium

The inhibition effect of tetrabutylphosphonium benzotriazolate (TBPB) on carbon steel in a 1mol·L-1 HCl solution was investigated using a combination of analytical techniques, including polarization curve, electrochemical impedance spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The study revealed that TBPB acts as a mixed corrosion inhibitor for carbon steel in acidic conditions. The efficiency of corrosion inhibition was observed to increase gradually with rising TBPB concentrations, reaching a maximum of 92% at a concentration of 10mmol·L-1. This enhancement in corrosion inhibition efficiency is attributed to the adsorption of TBPB on the metal surface, effectively isolating it from the corrosive medium and thereby preventing corrosion reactions. Importantly, this mechanism aligns well with the Langmuir isothermal adsorption model.

Enhancing copper corrosion resistance in highly caustic environments: Evaluation of environmentally friendly inorganic inhibitors and mechanistic insights

During this study, two inorganic glasses materials with chemical compositions of (1−x) (2Bi2 O3 ⋅B2 O3)–x BaO (with x=0.2 (BiB-Ba0.2) and x=0.6 and (BiB-Ba0.6)) were synthetized characterized and investigated as viable, ecofriendly, and sustainable inhibitors to mitigate copper corrosion in a highly caustic solution containing 0.5 M H2SO4 solution. To evaluate inhibition processes, several techniques were employed, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Furthermore, the results show that the two inhibitors studied, BiB-Ba0.2 and BiB-Ba0.6, have higher corrosion inhibition efficiencies at the optimum concentration (10−3 M), reaching 91.2 % and 90.8 %, respectively. Moreover, these findings suggest that the two inorganic compounds elaborated possess inhibitors of mixed types. Copper oxide (Cu2O) production is markedly delayed when the two inhibitors are added to the acid medium, according to the findings of the XRD, FTIR, SEM/EDS, and AFM investigations. This outcome is explained by the development of a shield that lessens surface damage to copper metal, producing a smoother surface morphology.

Non-enzymatic cholesterol biosensor: Electrochemical sensing based on peptide-polylactic acid thin film

Cholesterol is a fundamental lipid prevalent in eukaryotic cell membranes and circulating in the bloodstream bound to lipoproteins. It serves as a precursor to steroid hormones and is regarded as a biomarker for cardiovascular disease and other metabolic disorders. Numerous cholesterol detection methods predominantly rely on enzymes, which suffer from instability, leading to non-cost-effective biosensors with low sensitivity and poor reusability. Therefore, monitoring cholesterol levels with a feasible, rapid, and stable biosensor is critical for diagnosing and treating various disorders. This study aimed to develop a non-enzymatic cholesterol biosensor based on a selected cholesterol recognition peptide as the detection element. Screen-printed carbon electrodes (SPEs) modified with biocompatible poly-L-lactic acid (PLLA) porous nanomembranes (NMs) were utilized as support for the covalent immobilization of the peptide. Data obtained from electrochemical impedance spectroscopy (EIS) demonstrated the peptide's effective binding affinity towards cholesterol, paving the way for its implementation. The determination of cholesterol with the proposed biosensor exhibited a low limit of detection of 6.31 μM with linear responses ranging from 2–15 μM and 20–40 μM. These findings present an alternative method for cholesterol sensing by integrating novel peptides as biorecognition motifs with biocompatible polymeric materials, potentially useful as biocompatible and future point-of-care sensors.

Structural and Electrochemical Characterisation of NBZFO Cobalt-Free Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells: An Experimental Investigation

Compared to other energy-generating technologies and energy conversion devices, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have gained significant attention from energy experts due to its high energy density, moderate operating temperature (600–800°C), low emissions and reliability. Enhancing the performance of IT-SOFCs requires suitable and excellent cathode materials. Thus, a perovskite-type Nd0.5Ba0.5Zr0.8Fe0.2O3+δ (NBZFO) material was synthesised via traditional solid-state reaction technique and analysed as a potential cathode material for IT-SOFCs. Analysis of X-ray diffraction data (XRD) revealed a single-phase perovskite material that crystallises in cubic space group (pm-3m). The thermal and electrochemical properties were analysed with the aid of thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). NBZFO has an electrical conductivity in air of 80 S cm−1 at 400°C and a polarisation resistance (Rp) of 0.106 Ω cm2 at 800°C. TGA reveals a slight loss in weight of about 0.58%, thereby suggesting a highly stable cathode material for IT-SOFC. Electrochemical investigation shows that NBZFO has good electronic and ionic conductivity and excellent oxygen stichometry. Further studies are required to understand the effects of varying B-site composition of the cathode material.