Electroanalysis最新文献

Over the past century, human activities have contributed to the widespread rise in tellurium contamination in the environment and water bodies. Certain forms of tellurium are toxic, and exposure to these forms can have adverse health effects. To address this issue, an electrochemical sensor was developed using a bare indium tin oxide (ITO) working electrode and square wave stripping voltammetry for the detection and quantification of Te(IV) ions. For Te(IV) detection, a deposition potential of −0.9 V was applied to the working electrode for 180 s. Calibration curves of peak current and peak area versus Te(IV) concentration were constructed in acetate buffer at pH 4.50. The electrochemical sensor achieved a detection limit of 0.5 ppb, comparable to other studies with different working electrodes. Interference studies were conducted to investigate the impact of other metal ions on the quantifiable stripping peak of Te(IV).

Polyanions have been introduced as replacements for poly(vinyl chloride) (PVC) and potassium tetrakis(4-chlorophenyl)borate (KTpClPB) in the preparation of solid contact potassium-ion selective electrodes (K⁺-ISEs). Partly carboxylated PVC (PVC-COOH) and a fully charged polyanion, sodium poly(4-styrenesulfonate) (NaPSS), were used, culminating in the fabrication of three-component ion-selective membranes (ISMs). The comparison with a PVC-based ISM showed significantly reduced potential drifts during conditioning (from ∼1.3 to ∼0.2 mV/h) and a constant drift rate. Reduced drift is attributed to the presence of counter-charges in the polymer and the large molecular weight of the polyanions, therefore decreasing the leaching of the components resulting in degradation of the membrane. The ISEs utilizing the hydrophilic and highly charged NaPSS as the polymer matrix exhibit similar water layer formation compared to the PVC-based ISEs, and maintained a sensitivity of 54 ± 1 mV/dec and a selectivity over sodium of −3.1 (log $$) after 1 week in solution, suggesting an alternative approach to the standard membrane preparation protocol.

Polyanions have been introduced as replacements for poly(vinyl chloride) (PVC) and potassium tetrakis(4-chlorophenyl)borate (KTpClPB) in the preparation of solid contact potassium-ion selective electrodes (K⁺-ISEs). Partly carboxylated PVC (PVC-COOH) and a fully charged polyanion, sodium poly(4-styrenesulfonate) (NaPSS), were used, culminating in the fabrication of three-component ion-selective membranes (ISMs). The comparison with a PVC-based ISM showed significantly reduced potential drifts during conditioning (from ∼1.3 to ∼0.2 mV/h) and a constant drift rate. Reduced drift is attributed to the presence of counter-charges in the polymer and the large molecular weight of the polyanions, therefore decreasing the leaching of the components resulting in degradation of the membrane. The ISEs utilizing the hydrophilic and highly charged NaPSS as the polymer matrix exhibit similar water layer formation compared to the PVC-based ISEs, and maintained a sensitivity of 54 ± 1 mV/dec and a selectivity over sodium of −3.1 (log $$) after 1 week in solution, suggesting an alternative approach to the standard membrane preparation protocol.

Over the past century, human activities have contributed to the widespread rise in tellurium contamination in the environment and water bodies. Certain forms of tellurium are toxic, and exposure to these forms can have adverse health effects. To address this issue, an electrochemical sensor was developed using a bare indium tin oxide (ITO) working electrode and square wave stripping voltammetry for the detection and quantification of Te(IV) ions. For Te(IV) detection, a deposition potential of −0.9 V was applied to the working electrode for 180 s. Calibration curves of peak current and peak area versus Te(IV) concentration were constructed in acetate buffer at pH 4.50. The electrochemical sensor achieved a detection limit of 0.5 ppb, comparable to other studies with different working electrodes. Interference studies were conducted to investigate the impact of other metal ions on the quantifiable stripping peak of Te(IV).

This study introduces, for the first time, a novel voltammetric strategy based on integrating a stencil-printed electrode (StPE) with a hydrogel (HG) serving as the electrolytic medium. The electrode was fabricated using a laboratory-made conductive ink composed of graphite (as the conductive material), glass varnish (as the polymeric binder), and an acetate sheet (as the substrate). The HG selected for this study consisted of sodium polyacrylate, a polymer commonly used for plant irrigation and decorative purposes due to its high water-retention capacity. The StPE sensors were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the HG was thoroughly characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDX). Additionally, the kinetic parameters of HG absorption were evaluated by fixing the hydration time at 6 h. As a proof of concept, uric acid (UA), a clinically relevant biomarker, was selected as the model analyte. A differential pulse voltammetry (DPV) method was developed to monitor UA in synthetic urine samples. The sensor exhibited a linear response in the concentration range of 2.0–10.0 µmol L⁻¹, with excellent detectability (limit of detection = 0.146 µmol L⁻¹). The method also demonstrated good precision (RSD < 4.4%) and accuracy, with recovery rates ranging from 94% to 105% in spiked samples. The sustainable characteristics of the StPE sensor, combined with its effective performance in the HG medium, highlight the potential of this platform for electrochemical analysis of other clinically, environmentally, and forensically relevant analytes, offering broad opportunities for future innovations.

This study introduces, for the first time, a novel voltammetric strategy based on integrating a stencil-printed electrode (StPE) with a hydrogel (HG) serving as the electrolytic medium. The electrode was fabricated using a laboratory-made conductive ink composed of graphite (as the conductive material), glass varnish (as the polymeric binder), and an acetate sheet (as the substrate). The HG selected for this study consisted of sodium polyacrylate, a polymer commonly used for plant irrigation and decorative purposes due to its high water-retention capacity. The StPE sensors were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the HG was thoroughly characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDX). Additionally, the kinetic parameters of HG absorption were evaluated by fixing the hydration time at 6 h. As a proof of concept, uric acid (UA), a clinically relevant biomarker, was selected as the model analyte. A differential pulse voltammetry (DPV) method was developed to monitor UA in synthetic urine samples. The sensor exhibited a linear response in the concentration range of 2.0–10.0 µmol L⁻¹, with excellent detectability (limit of detection = 0.146 µmol L⁻¹). The method also demonstrated good precision (RSD < 4.4%) and accuracy, with recovery rates ranging from 94% to 105% in spiked samples. The sustainable characteristics of the StPE sensor, combined with its effective performance in the HG medium, highlight the potential of this platform for electrochemical analysis of other clinically, environmentally, and forensically relevant analytes, offering broad opportunities for future innovations.

This study evaluates zinc anode substrate materials for zinc–nickel flow batteries, including stainless steel strip, Cu–Ni–Mn alloy, Monel alloy, and Nickel-plated strip. Monel alloy and Nickel-plated steel strip exhibit higher zinc deposition potential, with the Nickel-plated strip showing a low equilibrium potential (E₀ = −1.430 V) and minimal reaction resistance (0.110 Ω), similar to zinc. The Nickel-plated strip also maintains a higher battery capacity after cycling, likely due to the smooth zinc deposition and minimal grain distance, making it the preferred anode substrate.

This study presents the development of lab-made graphite and silver conductive inks for the fabrication of mask-based printed electrodes. The graphite ink was formulated using glass varnish, graphite powder, acetone, and propylene glycol, whereas the silver ink was composed of silver powder, glass varnish, and acetone. The influence of ink composition, curing temperature, and curing time on the electrical properties of the inks was investigated. The optimized graphite ink containing 6.4% propylene glycol exhibited the best electrochemical performance, with a curing temperature of 40°C for 15 min. Silver ink, used as the pseudo-reference electrode, was cured at 25°C for 5 min. The electrodes were fabricated by printing inks on a polyester substrate, and their electrochemical behavior was evaluated using cyclic voltammetry in a Fe(CN)₆^3−/4− redox probe. Miniaturization of the electrochemical cell was achieved, reducing the working electrode area from 24.54 to 8.35 mm². The electrodes underwent electrochemical pretreatment in an alkaline medium, resulting in improved electron transfer kinetics and increased peak current. Scanning electron microscopy revealed a homogeneous and rough electrode surface with an increased electroactive area after pretreatment. The reproducibility and stability of the electrodes were assessed, and they demonstrated satisfactory performance over multiple cycles and different fabrication batches. The cost analysis showed that lab-made electrodes could be produced at a significantly lower cost compared to commercial electrodes. The graphite and silver inks developed provide a cost-effective and reliable solution for the fabrication of electrodes, offering potential applications in electrochemical sensing and analysis.

This study evaluates zinc anode substrate materials for zinc–nickel flow batteries, including stainless steel strip, Cu–Ni–Mn alloy, Monel alloy, and Nickel-plated strip. Monel alloy and Nickel-plated steel strip exhibit higher zinc deposition potential, with the Nickel-plated strip showing a low equilibrium potential (E₀ = −1.430 V) and minimal reaction resistance (0.110 Ω), similar to zinc. The Nickel-plated strip also maintains a higher battery capacity after cycling, likely due to the smooth zinc deposition and minimal grain distance, making it the preferred anode substrate.

3D printing, particularly fused deposition modeling, is an important technology applied in the electrochemical field and typically requires surface activation procedures to remove excess of polymeric material and expose the conductive material. The laser ablation method presents advantages, such as low cost, speed, and elimination of chemicals. In this context, this study aims to investigate the modification of graphene/polylactic acid electrode (Gp/PLA) using blue-laser treatment for the improved detection of paracetamol (PAR). 2D Gp/PLA printed layers were deposited on an insulating polycaprolactone substrate to generate a compact three-electrode system in a planar configuration for microliter-drop analysis. The blue-laser-treated electrodes (BL) were obtained using optimized conditions of laser power and speed of 280 mW and 30 mm s⁻¹, respectively. The Gp/PLA-BL electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The SEM images showed the removal of PLA, which was also confirmed by FTIR and XPS spectra. Before the treatment, cyclic voltammograms at 50 mV s⁻¹ of inner-sphere [Fe(CN)₆]^3−/4− redox pair exhibited an ill-defined voltammetric profile (ΔEp = 502 ± 4 mV) while an increase in the reversibility was achieved (ΔEp = 120 ± 1 mV) after the blue-laser ablation. Additionally, the lower charge transfer resistance was measured by electrochemical impedance spectroscopy after the treatment. As a proof-of-concept, analytical curves were constructed for PAR detection in a single drop using both non-treated and treated printed electrodes. An increase in the sensitivity of 2.4-fold was observed after the treatment.