Search Results (1,806)

Capacitive de-ionization (CDI) holds great promise for water desalination, while the widely used activated carbon (AC) electrodes suffer from a low salt adsorption capacity (SAC) and poor long-term stability due to the co-ion effect and electrode oxidation. Inspired by membrane-based CDI, we deposited polyethyleneimine (PEI), an ion exchange polymer with positive charge and ion selectivity, onto an AC electrode to serve as an anode for addressing these issues. Firstly, compared to traditional AC and commercial AEM-AC, the PEI-doped AC (PDAC) anode delivered a superior SAC of 36.3 mg/g, as the positively charged PEI enhanced electrostatic attraction, suppressed the co-ion effect, and offered extra sites. However, it showed poor cycling stability with 77.1% retention, owing to mass loss and anode oxidation. We further developed an electrode coated with a PEI-based membrane (PMAC), which exhibited a balanced performance with a high SAC of 33.4 mg/g and significantly improved long-term retention of 97.5%. The hydrophilic PEI membrane, strongly adhered to the AC surface, shortened the ion diffusion resistance and effectively prolonged the electrode lifespan. A systematic comparison between AC, AEM-AC, PDAC, and PMAC revealed the mechanism for PMAC’s notable enhancement. These findings establish a framework for designing novel CDI electrodes and advancing sustainable water desalination. Full article

The potential for structural health monitoring (SHM) in fibre-reinforced polymers (FRPs) using electrical resistance measurements (ERMs) has gained increasing attention, particularly in carbon fibre-reinforced polymers (CFRPs). Most existing studies are limited to single-axis measurements on coupon-scale specimens, whereas industrial applications demand scalable solutions capable of monitoring large areas, with more complex sensing configurations. Structural health monitoring (SHM) of carbon fibre-reinforced polymers (CFRPs) using electrical resistance measurements offers a low-cost, scalable sensing approach. However, predicting surface resistance between arbitrarily placed electrodes on unidirectional (UD) CFRP laminates remains challenging due to anisotropic conductivity and geometric variability. This study introduces a practical analytical model based on two geometry-dependent parameters, effective width and effective distance, to estimate resistance between any two electrodes arbitrarily placed on UD CFRP laminates with 0° or 90° fibre orientations. Validation through finite element (FE) simulations and experimental testing demonstrates good matching, confirming the model’s accuracy across various configurations. Results show that the dominant electrical current path aligns with the fibre direction due to the material’s anisotropic conductivity, allowing simplification to a single-axis resistance model. The proposed model offers a reliable estimation of surface resistance and provides a valuable tool for electrode array configuration design in CFRP-based SHM. This work contributes to enabling low-cost and scalable electrical sensing solutions for the real-time monitoring of composite structures in aerospace, automotive, and other high-performance applications. Full article

Environmental problems arising from conventional production models have posed a significant challenge in the search for renewable sources as raw materials for the production of everyday chemical compounds through more sustainable alternatives. The objective of the present work was the electrochemical synthesis of organic acids from the liquid of the natural and technical cashew nut shell (CNSLn and CNSLt), employing chronopotentiometry using a potentiostat and a graphite working electrode. Two concentrations (0.01–0.1% v/v) of CNSLn and CNSLt, two concentrations of NaOH as supporting electrolyte (0.125–2 M), and two current densities (40–60 mA/cm²) were tested in the experiments. Organic acids were detected and quantified by HPLC. To characterize the redox processes occurring in the constituents of CNSL, spectroelectrochemical analysis (FTIR–cyclic voltammetry), FTIR, and chronoamperometry were performed. The maximum concentrations obtained in the treatments were: acetic acid (828.86 mg/L), lactic acid (531.78 mg/L), and formic acid (305.4 mg/L), while other acids present in lower concentrations included oxalic, propionic, citric, and malonic acids. Voltammetry characterizations showed three irreversible oxidation processes in the anodic wave during the first cycle, indicating that the first process involved the formation of the phenoxy radical, the second process the formation of hydroquinones and benzoquinones, and the third process the cleavage of the aromatic ring and the aliphatic chain to form the organic acids. Furthermore, another oxidation pathway was observed, consisting of a fourth process in the second voltammetry cycle, corresponding to the nucleation of the phenoxy radical, evidenced as the formation of the C–O–C bond visible at 1050 cm⁻¹ in the infrared spectrum. From this route, a polymer was formed on the electrode surface, which limited the yield of organic acid synthesis. Finally, this research provides new insights in the field of electrochemistry, specifically in the synthesis of organic acids from CNSL as a renewable feedstock, with the novelty being the production of oxalic, propionic, citric, and malonic acids. Full article

The combination of microplasma generation and optical multi-material fiber technologies enables real-time diagnostics. The stack-and-draw technique has emerged as a promising method for creating multimaterial fibers suitable for plasma-based diagnostics. The elaboration of such devices for the generation of long-lasting microplasma for real-time and remote analyses remains challenging due to the difficulties of reaching long lengths without defects and with continuous electrodes. Post-functionalization of the electrode surface is also required to increase the plasma emission duration. In this study, glass was preferred over polymers for producing rectangular fibers (ribbons) that are easy to stack without wasting space and are resistant to high operating temperatures. Conversely, an aluminum alloy was chosen for the electrodes to reduce discontinuity defects. With the chosen bi-electrode geometry, the cooling rate during drawing has to remain between 200 and 300 °C/s to limit defect formation and guarantee low electrical resistivity. During plasma generation, an in situ oxide layer forms on the tip of each electrode. This results in a significant increase in plasma emission duration without the need for an additional post-functionalization step after drawing. These ribbons were tested in combination with an optical emission spectrometer to create a miniature gas detector for hydrocarbons. Full article

Water-induced corrosion and zinc dendrite formation seriously disrupt the Zn plating/stripping process at the anode/electrolyte interface, which results in the instability of the Zn metal anode in aqueous zinc-ion batteries. To address the issues of the zinc metal anode, three water-soluble polymers with different hydrophilic groups—polyacrylic acid (PAA), polyacrylamide (PAM), and polyethylene glycol (PEG)—were designed as electrolyte additives in ZnSO₄ electrolytes. Among them, the PAA-based system exhibited an optimal electrochemical performance, achieving a stable cycling for more than 360 h at a current density of 5 mA cm⁻² with an areal capacity of 2 mA h cm⁻². This improvement could be attributed to its carboxyl groups, which effectively suppresses zinc dendrite growth, electrode corrosion, and side reactions, thereby enhancing the cycling performance of zinc-ion batteries. This work provides a reference for the optimization of zinc anodes in aqueous zinc-ion batteries. Full article

Ionic Polymer–Metal Composites (IPMCs) are promising electroactive polymers for artificial muscles, as their bending motion depends on the induced current—greater current leads to greater bending. While conventional IPMCs use cation exchange membranes, this study explores IPMCs containing both immobile positive and negative charges, resembling real muscle tissue. Considering that an IPMC consists of an ion-exchange membrane sandwiched between two thin metal coatings serving as electrodes, we found that (i) improving the contact between the metal coating (electrode) and the ion exchange membrane is an effective way to enhance current induction. Achieving tight electrode membrane contact can drastically increase the induced current by up to four orders of magnitude, and even samples that previously showed no current induction can exhibit measurable current after improvement. (ii) Doping with mobile ions is another well-known method of enhancing IPMC current. However, we found that simply introducing dopants into the IPMC body is not effective; the choice of dopant is crucial. In this work, we identified silver ions as effective dopants for enhancing current induction. Considering that real muscles consume oxygen for activation, we also attempted to supply oxygen to the IPMC surface. We confirmed that (iii) supplying oxygen to the IPMC surface is another effective means of enhancing current induction, which in turn resulted in a significant improvement in IPMC bending performance. Full article

Phenolic compounds such as resorcinol (RS) have negative impacts on aquatic life, the environment, and human health. Thus, it is necessary to develop sensing devices for the monitoring of RS. The electrochemical method is one of the most significant approaches for the determination of toxic substances. In electrochemical methods, electrode modifiers play a vital role and affect the sensing performance of the electrochemical sensors. Thus, the selection of efficient electrode material is of great importance. In recent years, various electrode modifiers such as graphene, metal–organic frameworks (MOFs), MXenes, metal oxides, polymers, and composite materials have been extensively used for the fabrication of RS sensors. In this review, we have summarized the reported electrode modifiers for the fabrication of RS electrochemical sensors. Various electrochemical sensing techniques, including differential pulse voltammetry (DPV), square wave voltammetry (SWV), amperometry (Amp), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) have been discussed. This review provides an overview of a large number of electrode modifiers for the determination of RS. The limitations, challenges, and future perspectives for RS sensors are discussed. We believe that the present review article is beneficial for the scientific community and electrochemists working on the construction of RS sensors. Full article

Flexible upconversion (UC) devices, owing to their unique combination of high–efficiency optical energy conversion and mechanical flexibility, have attracted increasing attention in the fields of optoelectronics, wearable devices, flexible displays, and biomedical applications. However, significant challenges remain in balancing optical performance, mechanical adaptability, long–term stability, and scalable fabrication, which limit their practical deployment. This review systematically introduces five representative upconversion mechanisms—excited–state absorption (ESA), energy transfer upconversion (ETU), energy migration upconversion (EMU), triplet–triplet annihilation upconversion (TTA–UC), and photon avalanche (PA)—highlighting their energy conversion principles, performance characteristics, and applicable scenarios. The article further delves into the flexible transition of upconversion devices, detailing not only the evolution of the luminescent layer from bulk crystals and nanoparticles to polymer composites and hybrid systems, but also the optimization of electrodes from rigid metal films to metal grids, carbon–based materials, and stretchable polymers. These developments significantly enhance the stability and reliability of flexible upconversion devices under bending, stretching, and complex mechanical deformation. Finally, emerging research directions are outlined, including multi–mechanism synergistic design, precise nanostructure engineering, interface optimization, and the construction of high–performance composite systems, emphasizing the broad potential of flexible UC devices in flexible displays, wearable health monitoring, solar energy harvesting, flexible optical communications, and biomedical photonic applications. This work provides critical insights for the design and application of high–performance flexible optoelectronic devices. Full article

Approximately 3.8% of the global population suffers from depressive disorders, posing a substantial public health challenge exacerbated by the COVID-19 pandemic due to widespread unemployment and prolonged social isolation. The difficulty in objectively quantifying psychological states underscores the need for effective stress assessment methods. Herein, we developed a portable electrochemical cortisol sensor (PECS) for accurate mental stress assessment. The PECS consists of a screen-printed carbon electrode decorated with gold nanoparticles and a molecularly imprinted polymer (MIP) synthesized via electropolymerization. The as-prepared PECS demonstrates a wide and linear detection range from 1 fM to 1 μM, an ultra-low detection limit of 0.4112 fM and a high sensitivity of 15.518 nA∙lg(nM⁻¹)∙cm⁻². This work provides new possibility of developing soft bioelectronics for non-invasive and real-time mental health monitoring. Full article

Hydrophilic polymer–osmium complexes enhance electron transfer between enzymes and electrodes in biosensors. In this study, hydrophobic poly(4-vinylpyridine) (PVP) was quaternized with 2-bromoethanol to synthesize water-soluble PVP(Q)-C₂H₄OH polymers (MW 60,000 and 160,000). The resulting PVP(Q)-C₂H₄OH-Os(dmo-bpy)₂Cl complexes were verified by UV-Vis, FT-IR, 1H NMR, SEM-EDS, and zeta potential analyses, confirming successful quaternization and osmium coordination with good dispersion stability. Electrochemical tests (cyclic voltammetry, multi-potential step, amperometry) demonstrated that electrodes with quaternized mediators showed greatly enhanced catalytic currents for glucose (0–20 mM), with sensitivities of 6.9791 (MW 60,000) and 6.6279 μA·mM⁻¹·cm⁻² (MW 160,000), respectively, which were 6.6–10.3 times higher than those of non-quaternized polymers. Selectivity tests showed negligible interference from common species such as ascorbic acid, dopamine, uric acid, and serotonin. Continuous glucose monitoring (CGM) electrodes were fabricated by immobilizing the mediator and glucose dehydrogenase on silanized Au electrodes. SEM, scan rate, and impedance analyses confirmed stable binding. The modified electrodes showed strong linearity (R² = 0.992) and high sensitivity (2.56 μA·mM⁻¹·cm⁻²), and good stability, maintaining ~82% activity for seven days. Human plasma testing validated accurate glucose detection (6.05 mM), consistent with physiological levels. Overall, quaternized PVP(Q) mediators significantly improved solubility and electron transfer, enabling the development of a stable, selective glucose sensor suitable for CGM applications. Full article

Hepatitis C represents a critical global health crisis, causing approximately 1.4 million deaths annually. Although 98% of cases are treatable, only about 20% of infected individuals know their hepatitis C virus (HCV) status, highlighting the urgent need for rapid and more efficient diagnostic management. Viral genetic material can be detected in serum or plasma within just one week of exposure, making it the most reliable marker and the gold standard for active HCV infection diagnosis. In this study, a biosensor was developed to detect conserved nucleotide sequences of HCV using a 3D surface electrode composed of poly-L-lysine (PLL) and carbon nanotubes (CNTs). PLL is a positively charged biocompatible polymer rich in amine groups, attractive for the immobilization of proteins, DNA, and other biomolecules. PLL was employed to construct a 3D surface with vertically aligned CNTs, achieving a high electron transfer rate. Cyclic voltammetry technique and scanning electron microscopy (SEM) were used to characterize the sensor platform, and analytical responses were measured by differential pulse voltammetry. This HCV biosensor detected the hybridization event by a significant reduction in DPV peaks in the presence of the ferri/ferrocyanide redox probe, without any intercalator agents. DNA responses were observed in phosphate-buffered saline (PBS) and cDNA-spiked serum samples, demonstrating its analytical specificity. These findings represent advances in analytical tools that can effectively address the challenges of timely diagnosis for asymptomatic HCV carriers. Full article

As the environmental burden of traditional plastics continues to grow, bioplastics (BPs) have emerged as a promising alternative due to their renewable origins and potential for biodegradability. However, the most popular anaerobic systems (ASs)—anaerobic digestion (AD), acidogenic fermentation (AF), and enzyme hydrolysis (EH)—for BPs degradation still face many challenges, e.g., low degradation efficiency, process instability, etc. As a sustainable clean energy technology, bioelectrochemical systems (BESs) have demonstrated strong potential in the treatment of complex organic waste when integrated with ASs. Nevertheless, research on the synergistic degradation of BPs using BES-ASs remains relatively limited. This review systematically summarizes commonly used anaerobic degradation methods for BPs, along with their advantages and limitations, and highlights the BES-AS as an innovative strategy to enhance BPs degradation efficiency. BESs can accelerate the decomposition of complex polymer structures through the activity of electroactive microorganisms, while also offering benefits such as energy recovery and real-time process monitoring. When coupled with anaerobic digestion, the BES-AS demonstrates significant synergistic effects, improving degradation efficiency and promoting the production of high-value-added products such as volatile fatty acids (VFAs) and biogas, thereby showing great application potential. This review outlines current research progress, identifies key knowledge gaps in mechanism elucidation, system design, source recovery, etc., and proposes future research directions. These include system optimization, microbial community engineering, development of advanced electrode materials, and omics-based mechanistic studies. Advancing multidisciplinary integration is expected to accelerate the practical application of BES-ASs in BP waste management and contribute to achieving the goals of sustainability, efficiency, and circular utilization. Full article

Perfluorooctanesulfonate (PFOS) is a typical persistent organic pollutant, which presents a significant risk to the ecosystem and human health. Therefore, the development of a highly sensitive and effective detection technique for PFOS has aroused wide concern. In this study, for the mesoporous metal–organic frameworks (MOFs), Cr-MIL-101 were used as the precursor. And the poly(3,4-ethylenedioxythiophene) (PEDOT) using as molecularly imprinted polymers (MIPs) was loaded on Cr-MIL-101 to form a core–shell structure. The obtained Cr-MIL-101@PEDOT/MIP composites integrate the high specific surface area of Cr-MIL-101 and the specific recognition capability of PEDOT/MIP. The glassy carbon electrode (GCE) interface modified by them can specifically adsorb PFOS through electrostatic interactions, coordination by Cr metal nodes, hydrophobic interaction, and hydrogen bonding, etc. The adsorbed PFOS molecules could block the active sites at the electrode interface, causing the current decay of the redox probe. Following the quantitative analysis of peak current decay values using the Langmuir model and the Freundlich–Langmuir model, a wide detection range (0.1–200 nM) and a low detection limit (0.025 nM) were obtained. Characterization techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), and electrochemical methods were employed to validate the fabrication of the composites. Moreover, Cr-MIL-101@PEDOT/MIP/GCE showed satisfactory stability, repeatability, and selectivity, providing an effective method for the detection of PFOS in practical samples, showing a wide prospective application. Full article

Thorium has emerged as a promising alternative to uranium in nuclear energy systems due to its higher natural abundance, favorable conversion to fissile ²³³U, and reduced generation of long-lived transuranic waste. This review provides a comprehensive overview of advanced techniques for thorium recovery from primary ores and secondary resources. The main mineralogical carriers—including monazite, thorianite, thorite, and cheralite as well as industrial by-products such as rare-earth processing tailings—are critically examined with respect to their occurrence and processing potential. Physical enrichment methods (gravity, magnetic, and electrostatic separation) and hydrometallurgical approaches (acidic and alkaline leaching) are analyzed in detail, highlighting their efficiencies, limitations, and environmental implications. Particular emphasis is placed on modern separation strategies such as solvent extraction with organophosphorus reagents, diglycolamides, and ionic liquids, as well as extraction chromatography, nanocomposite sorbents, ion-imprinted polymers, and electrosorption on carbon-based electrodes. These techniques demonstrate significant progress in enhancing selectivity, reducing reagent consumption, and enabling recovery from low-grade and secondary feedstocks. Environmental and radiological aspects, including waste minimization, immobilization, and regulatory frameworks, are discussed as integral components of sustainable thorium management. Finally, perspectives on hybrid technologies, digital process optimization, and economic feasibility are outlined, underscoring the need for interdisciplinary approaches that combine chemistry, materials science, and environmental engineering. Collectively, the analysis highlights the transition from conventional practices to integrated, scalable, and environmentally responsible technologies for thorium recovery. Full article

In this work, we investigated the use of a piezoelectric flexible device for energy harvesting. The main goal of the study was to fill the nanostructured pores of anodic aluminum oxide (AAO) films with piezoelectric polymer (PVDF-TrFE) via a modified conventional screen printing technique using blade printing. In this way, it is possible to obtain a composite from nanostructured thin films of polymer nanorods that shows improved charge generation ability compared to other non-nanostructured composites or pure (non-composite) aluminum with similar dimensions. This behavior is due to the effect of the highly developed surface of the material used to fill in the AAO nanopore template and its ability to withstand the application of higher mechanical loads to the structured piezoelectric material during deformation. The contact blade print filling technique can produce nanostructured piezoelectric polymer films with precise geometric parameters in terms of thickness and nanorod diameters, at around 200 nm, and a length of 12 μm. At a low frequency of 17 Hz, the highest root-mean-square (RMS) voltage generated using the nanostructured AAO/PVDF-TrFE sample with aluminum electrodes was around 395 mV. At high frequencies above 1700 Hz, the highest RMS voltage generated using the nanostructured AAO/PVDF-TrFE sample with gold electrodes was around 680 mV. The RMS voltage generated using a uniform (non-nanostructured) layer of PVDF-TrFE was 15% lower across the whole frequency range. Full article