Search Results (1,208)

This study investigates the electrochemical properties of polymer-based microelectrode arrays (pMEAs) and their performance in measuring oxygen (O₂) and hydrogen peroxide (H₂O₂). Morphological characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed a uniform, fine-grained platinum surface with nanoscale roughness, consistent with the Ti/Pt/Au/Pt multilayer stack architecture. The electrochemical behavior of the pMEAs was assessed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which demonstrated favorable responses for both O₂ reduction and H₂O₂ oxidation, together with low impedance (41.1 kΩ at 1 kHz). For O₂ detection, amperometric measurements at −0.6 V vs. Ag/AgCl indicated a sensitivity of −0.25 ± 0.04 nA μM⁻¹ and a detection limit of 5.4 ± 1.4 nM. For H₂O₂ detection, application of +0.7 V vs. Ag/AgCl resulted in a sensitivity of 88.13 ± 7.61 nA mM⁻¹ and a detection limit of 41.9 ± 5.6 nM. Selectivity evaluation showed effective interferent exclusion following m-phenylenediamine electrodeposition, without compromising analytical performance. Overall, these findings indicate the suitability of pMEAs for real-time, in vivo monitoring of O₂ and H₂O₂ in brain tissue with high spatial and temporal resolution, supporting applications in oxidative stress research and neurometabolic sensing. Full article

In recent years, alternative recycling approaches such as melt quenching and electrochemical evaluation methods have been investigated to assess the quality and performance of recovered lead materials. In this study, several samples obtained from the recycling process were analyzed electrochemically. The objective was to compare their electrochemical parameters and identify the samples with better electrochemical performance. The main methods used in this paper are X-ray diffraction analysis and voltammetric investigations using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). Electrochemical characterization provides valuable information about the behavior of recycled lead materials. Parameters such as half-wave potential (E_1/2), anodic current density (I_a), and solution or bulk resistance (R_b) are commonly used to evaluate electrochemical activity and conductivity. The electrochemical analysis reveals noticeable differences among the samples studied. The analysis of CV, LSV, and EIS indicates that the samples P2 (doped with CuO and Sb₂O₃) and P3N (doped with CaO/Fe₂O₃/Fe) exhibit the most favorable electrochemical behavior for lead acid battery applications, with the highest current response and smallest peak separation, suggesting efficient Pb/PbSO₄ redox reactions and minimal polarization. Full article

In this study, an electrochemical immunosensor based on polyaniline/nano-Fe₃O₄ (PANI/Nano-Fe₃O₄) nanocomposite (PANI/Nano-Fe₃O₄/Anti-FLA/BSA/GCE) was developed for the highly sensitive and selective detection of trace levels of fluoranthene (FLA) in marine environments. Fluoranthene antibodies (Anti-FLA) were covalently immobilized on a glassy carbon electrode (GCE) modified with PANI/Nano-Fe₃O₄ via an EDC/NHS activation strategy, enabling specific recognition of FLA based on the antigen–antibody binding mechanism. The performance of the sensor was systematically optimized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The results demonstrated a linear inverse relationship between peak current (I_p) and FLA concentration in the range of 0.5~80 ng/mL, with a regression equation of I = −1.55C + 174.602 (R² = 0.996). The limit of detection (LOD) was as low as 0.354 ng/mL (S/N = 3). In real seawater sample analysis, spiked recovery tests at three representative sites in the Maowei Sea, Guangxi, yielded recoveries of 95.44%~97.51%, with RSDs below 3%, confirming the sensor’s resistance to matrix interference. The synergistic effect of the porous conductive network of PANI and the high specific surface area of Nano-Fe₃O₄ significantly amplified the electrochemical signal, while the molecular specificity of the antibody ensured targeted recognition. This sensor provides a novel and effective approach for the on-site rapid detection of polycyclic aromatic hydrocarbon (PAH) pollutants in complex marine environments, offering both high sensitivity and selectivity. Full article

Sustaining human presence on the Moon depends on access to strategic metals, which can be achieved by directly utilizing extraterrestrial resources through in situ resource utilization (ISRU). This study presents novel insights and preliminary results into a previously unexplored strategy for metals extraction from the lunar regolith simulant Lunar Mare Soil (LMS-1) using deep eutectic solvents (DESs). Based on inductively coupled plasma–optical emission spectrometry (ICP-OES) measurements, the solubility of major oxide components of the regolith, SiO₂, Al₂O₃, TiO₂, Cr₂O₃, MgO and FeO_T, was investigated in ethaline (choline chloride:ethylene glycol, ChCl:EG) as well as reline (ChCl:Urea). Although both DESs enabled oxide dissolution, reline exhibited significantly higher dissolution efficiency, due to the additional hydrogen-bond donor sites, NH and CO groups from urea, as well as high chloride activity in the reline. Cyclic voltammetry (CV) and square wave voltammetry (SWV) revealed that dissolved metal species in the reline–regolith system undergo complex multivalent redox transitions. The equilibrium potentials of the metals were determined and correlated with the order in which the metals should be electrodeposited on the cathode from an electrolyte containing dissolved lunar regolith. Based on the data from electrochemical measurements, parameters for electrolysis were selected. At less negative overpotentials, the deposit consisted mainly of Si, while Al, Cr, and Fe, along with Si, were electrodeposited at more negative potentials. The results highlight the importance of considering the selective electrochemical extraction of metals from DESs using lunar regolith as the source. Full article

This study investigates the impact of acetone on the electrochemical behaviour of 3D nickel foam electrodes in 0.1 M NaOH solution, with respect to the kinetics of alkaline water electrolysis (hydrogen and oxygen evolution reactions: HER and OER, respectively). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarisation techniques were employed to investigate the kinetics of these processes for (CH₃)₂C=O concentrations ranging from 1.0 × 10⁻⁵ to 0.1 M. The fundamental conclusions of this work are related to the fact that acetone, at moderate concentrations, was found to significantly facilitate the kinetics of both the HER and the OER processes, when examined on unmodified Ni foam electrodes. Conversely, the presence of acetone in working electrolyte for a Ru-activated nickel foam electrode resulted in a radical inhibition of the HER kinetics. The above is strongly believed to be associated with an electrode surface poisoning effect, in relation to the Ru sites’ blockage by an extensive, flat/side-on coordination of adsorbed acetone molecules. Interestingly, in the presence of Ru, acetone had practically no effect on the recorded OER rates. The above indicates that some organic additives (e.g., acetone) might exhibit significant, although strongly catalyst-dependent, opportunities for facilitation of the industrial alkaline water electrolysis process. Full article

Osteosarcoma, the most common primary malignant bone tumor in adolescents, faces treatment challenges due to metastasis and chemoresistance. This study developed a novel Au@Rh core–shell nanoparticle system functionalized with indocyanine green (ICG) to overcome hypoxia-limited photodynamic therapy (PDT). Au@Rh nanoparticles were synthesized via wet chemistry and characterized by UV-Vis spectroscopy, TEM, and cyclic voltammetry (CV). The system exhibited a core–shell morphology, well-defined crystalline planes, photothermal conversion and electrocatalytic activity. The Au@Rh nanoparticles (109 nm total size, 90 nm Au core, and 15 nm Rh shell) demonstrated dual functionality: the gold core provided photothermal conversion (a 7 °C temperature increase under NIR irradiation), while the rhodium shell exhibited pH-independent electrocatalytic activity for H₂O₂ decomposition, generating oxygen to alleviate tumor hypoxia. Crucially, the system showed excellent biocompatibility, with no significant cytotoxicity in both osteosarcoma (HOS) or normal osteoblast (hFOB) cells after 48 h of exposure. When activated by NIR irradiation (808 nm, 16.6 J/cm²), the complete Au@Rh-ICG system achieved selective 67% cytotoxicity in HOS cells versus only 30% in hFOB cells, demonstrating targeted therapeutic efficacy. These results position Au@Rh-ICG as a promising theranostic platform for osteosarcoma treatment, combining enhanced PDT with photothermal therapy while addressing tumor hypoxia. Full article

The integration of carbon nanomaterials with organic compounds offers a promising strategy for developing next-generation electrode materials with superior properties. A novel type of carbon paste electrode was fabricated by modifying a graphite matrix with functionalized multiwalled carbon nanotubes and juglone as a redox mediator, and then it was deposited by manual packing into a PEEK body (JUG-MWCNT/CPE). The surface morphology and structural parameters of the composite materials were meticulously characterized using scanning electron microscopy (SEM), nitrogen adsorption–desorption isotherms, and spectroscopic techniques, while their electrochemical properties were rigorously evaluated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). This study demonstrates that the synergistic interaction between the conductive nanotube network and the electroactive juglone significantly reduces the oxidation overpotential and enhances the peak current response of melatonin. Under optimized DPV parameters, the developed sensor presents outstanding analytical performance, featuring a wide linear response range from 0.002 to 0.16 mg L⁻¹, a low detection limit of 0.49 µg L⁻¹, excellent long-term signal stability for up to 30 days, and valid applicability for real-sample monitoring in commercial tablets and dietary supplements. Full article

This study establishes a unified electrochemical–optical framework to elucidate adsorption-controlled charge transfer and electronic excitation at platinum–electrolyte interfaces modified by biomolecules and metal nanoparticles. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and UV-Vis absorption spectroscopy with Tauc analysis were used to probe transformations induced by vitamin B6 (pyridoxine) and silver nanoparticles (nAg) in Na₂SO₄ aqueous electrolytes. In the supporting electrolyte, platinum behaves as a blocking capacitive interface with nearly symmetric anodic–cathodic charges, high charge-transfer resistance (R_ct ≈ 3.14 kΩ·cm²), low double-layer capacitance (C_dl ≈ 4.0 × 10⁻⁵ F·cm⁻²), and deep-UV transitions (E_low ≥ 3.8 eV), confirming the electrochemical inertness of sulfate media. Vitamin B6 molecules interact with the electrode surface and modify the structure of the electrical double layer at the platinum/electrolyte interface, restructuring the double layer, increasing C_dl (≈1.2 × 10⁻⁴ F·cm⁻²), decreasing R_ct (≈0.23 kΩ·cm²), and generating irreversible surface-confined anodic processes. Tauc plots yield two transitions (E_low ≈ 2.9 eV; E_high ≈ 4.1 eV), attributed to molecular states and weak charge-transfer interactions. The results suggest electronic interactions between the silver nanoparticles and the adsorbed vitamin B6 molecules at the electrode interface. Strong electronic interactions between vitamin B6 and nAg yields ultralow R_ct (≈58 Ω·cm²), enhanced pseudocapacitance (C_dl ≈ 2.9 × 10⁻⁴ F·cm⁻²), and red-shifted transitions (E_low ≈ 2.2 eV; E_high ≈ 3.7 eV). These results show that adsorption-induced electronic coupling governs interfacial kinetics and optical excitation pathways. Full article

Recently, numerous synthesis methods have been developed for the preparation of nanostructured materials for supercapacitor applications, and top-down strategies have gained increasing attention due to their relative simplicity and reduced processing complexity. In particular, the combustion method is recognized as one of the simplest and most rapid approaches for producing a wide range of materials. Within this study, the combustion of Cu₄₈Zr₄₇Al₅ amorphous ribbons was employed, and the supercapacitor electrodes based on Cu-Cu₂O/ZrO₂ mixed oxide were developed. The morpho-structural properties of the materials were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the electrochemical performance, particularly for supercapacitor applications, was evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements. The CV curves indicate that the Cu–Cu₂O/ZrO₂ mixed oxide structure acts as a positive electrode and exhibits a non-rectangular shape, confirming pseudocapacitive behavior of the as-synthesized material. A maximum areal specific capacitance of 472.7 mF cm⁻² was obtained at a scan rate of 5 mV s⁻¹. From GCD analysis, an areal specific capacitance of 336.5 mF cm⁻² was achieved at a current density of 1 mA cm⁻². Cycling stability was evaluated over 1000 charge–discharge cycles, showing an increase in capacitance to 135.14% after the 1000th cycle, attributed to the progressive activation of the electrode material. This study highlights the potential of Cu–Cu₂O/ZrO₂ mixed oxides prepared via self-sustained combustion as efficient and durable electrode materials for supercapacitors. The findings provide a starting point for the future optimization of amorphous alloys for the synthesis of mixed-oxide materials through a scalable fabrication process, paving the way for advanced energy storage applications. Full article

Electroless nickel–phosphorus (Ni–P) coatings were deposited on steel substrates for 20, 40, and 60 min to examine the effect of deposition time on their pseudocapacitive behavior in an alkaline electrolyte. The coatings were characterized by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). Although coating mass, thickness, and roughness increased monotonically with deposition time, the electrochemical response showed a pronounced maximum at 40 min. The 40 min coating exhibited the highest areal capacitance in both CV and GCD measurements, reaching 33.1 ± 1.8 mF cm⁻² at 10 mV s⁻¹ and 426.5 ± 9.8 mF cm⁻² at 5 mA cm⁻², whereas the 60 min coating showed substantially lower capacitance. SEM and AFM confirmed progressive nodular coarsening and increasing surface roughness with time, but these geometric parameters alone did not explain the non-monotonic capacitance trend. In contrast, XPS revealed that the 40 min coating possessed the highest surface Ni content, while prolonged deposition led to a more P-enriched outermost surface. EIS further showed that the 40 min coating had the most favorable local high-frequency interfacial response, whereas the 60 min coating exhibited the highest local polarization. The results demonstrate that the electrochemical performance of electroless Ni–P coatings is more closely associated with the composition and accessibility of the activated near-surface region than with coating thickness or roughness alone, and that 40 min represents an interfacial optimum under the applied deposition conditions. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

A nitrogen/sulfur co-doped reduced graphene oxide (N,S-RGO) material was rationally prepared via a modified Hummers method followed by microwave-assisted reduction. The resulting material was uniformly deposited onto a glassy carbon electrode (GCE) to fabricate an electrochemical sensor for nitrobenzene (NB) detection. The prepared N,S-RGO material was characterized in detail using Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, confirming the successful incorporation of heteroatoms. Furthermore, electrochemical studies, including cyclic voltammetry (CV) and linear sweep voltammetry (LSV), revealed the enhanced electrical conductivity of the material. The fabricated N,S-RGO/GCE sensor exhibited remarkable electroanalytical performance, achieving a low detection limit (LOD) of 7 nM within a linear concentration range of 0.05 to 147 µM. The enhanced sensing performance is attributed to the synergistic effect of nitrogen and sulfur doping, which improves electron transfer kinetics and abundant active sites for NB reduction. Furthermore, the sensor demonstrated outstanding selectivity toward NB in the presence of common interfering substances. Its practical applicability was confirmed through the successful detection of NB in environmental water samples, yielding convincing recovery rates. These results highlight the potential of the N,S-RGO/GCE platform as an efficient and reliable electrochemical sensor for environmental monitoring of NB contamination. Full article

The development of efficient catalysts for the glycerol oxidation reaction (GOR) is crucial for advancing direct glycerol fuel cells. This study provides mechanistic insights into the glycerol electro-oxidation reaction (GOR) on Co@Pt/C, Ni@Pt/C, and Sn@Pt/C catalysts using in situ FTIR spectroscopy. While the structural and electrochemical properties of these materials have been previously reported, their reaction pathways and product selectivity under alkaline conditions remain unclear. Electrochemical performance was evaluated through cyclic voltammetry (CV) and chronoamperometry (1.0 M KOH + 1.0 M glycerol), revealing that the bimetallic catalysts exhibited superior catalytic activity compared to Pt/C. Co@Pt/C demonstrated the highest performance, with a 7.5-fold increase in current density relative to Pt/C, followed by Sn@Pt/C (3.4-fold) and Ni@Pt/C (2.8-fold). In situ FTIR analysis identified key oxidation products, including C3, C2, and C1 species, with evidence of both partial and complete oxidation. These findings demonstrate that the core metal plays a key role in governing reaction pathways and C–C bond cleavage, providing important insights for the rational design of anode materials in direct glycerol fuel cells. Full article

Direct ammonia fuel cells (DAFCs) offer a promising pathway for carbon-free energy conversion but their practical performance is limited by sluggish cathode kinetics. In this work, non-precious FeCoN catalysts offer a cost-effective solution, yet carbon support optimization is crucial for activity and stability. FeCoN/XC-72R, FeCoN/CNT, and FeCoN/CNH cathode catalysts were synthesized by annealing at 550–750 °C. Their structure and morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical behavior was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in alkaline medium containing KOH and NH₄OH. FeCoN/XC-72R exhibited the lowest resistance of 27 Ω and superior activity. In single cell tests using a 40 wt% PtIr/C anode catalyst at 2 mg cm⁻², the FeCoN/XC-72R catalyst achieved the highest power density of 71 mW/cm² under optimized conditions of 0.1M NH₄OH + 3M KOH, 100 °C, and O₂ feed. Among the carbon supports, carbon black (XC-72R) proved the most effective support for FeCoN catalysts in low concentration DAFCs, outperforming carbon nanotubes (CNTs) and carbon nanohorns (CNHs). These findings highlight the importance of carbon support selection in the design of efficient cathodes for next generation low concentration direct ammonia fuel cells. Full article

In this work, we employed an easy hydrothermal method to prepare CuO and ZnO, as well as the prepared composite nanostructured electrodes of CuO@ZnO for supercapacitor applications. The systematic electrochemical performance evaluation of the prepared materials was conducted by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). CuO@ZnO nanocomposite reflected the best charge storing behavior with a specific capacitance of 513 F/g, followed by pristine CuO (190 F/g) and ZnO (416 F/g). The composite also demonstrated 25.67 Wh/kg and 400 W/kg for energy density and power density, respectively, suggesting improved electrochemical performance. Besides, the areal and volumetric capacitances were 0.77 F/cm² and 4.81 F/cm³, respectively, supported by the structural integrity and enhancement in electroactive materials utilization of the electrode material. Kinetic analysis showed that b values of the samples had mixed capacitive/diffusion-controlled charge storage, while higher diffusion coefficients and standard rate constants were apparent for ion transport or redox kinetics. EIS results showed a 2.14 Ω solution resistance, indicative of a decreased electrical resistivity. An asymmetric supercapacitor device fabricated by CuO@ZnO as the positive electrode and activated carbon (AC) as the negative electrode provided the specific capacitance of 48.57 F/g, energy density of 15.17 Wh/kg, and power density of 535 W/kg. After 10,000 cycles, the capacitance of the device was 76%, indicating good long-term stability. Full article