Single‐entity electrochemistry (SEE) was employed to quantitatively investigate the adsorption–desorption behavior of Cd 2+ on individual graphene oxide (GO) and Fe 3 O 4 particles, providing nanoscale insight into interfacial processes that are inaccessible to bulk methods. Distinct collision signals were observed for the two adsorbents, where GO generated larger and broader current spikes, reflecting higher Cd 2+ loading and slower electron transfer. Adsorption isotherms constructed from SEE data closely followed the Langmuir model and yielded comparable affinity constants and separation factors (0 < R L < 1) to traditional batch experiments, confirming the quantitative accuracy of SEE. Desorption kinetics for both materials were well described by the pseudo‐second‐order model, revealing chemisorption‐controlled behavior. Fe 3 O 4 exhibited faster, more uniform desorption (constant CV%), whereas GO showed slower and more heterogeneous release due to stronger surface complexation. In mixed‐particle systems, desorption kinetics remained independent, though GO increased Fe 3 O 4 's event‐to‐event variability, indicating subtle interparticle interactions. Overall, SEE provides a reliable, real‐time, and particle‐resolved approach for linking electrochemical dynamics with adsorption thermodynamics in complex adsorbent systems.

The escalating global energy crisis underscores the urgent need to develop advanced energy conversion and storage technologies. However, zinc‐air batteries are hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), necessitating the development of low‐cost, non‐precious metal catalysts to enhance their reaction efficiency. Meanwhile, although the nitrate electroreduction reaction offers a greener alternative compared to the traditional Haber–Bosch process for ammonia synthesis, it also requires the assistance of efficient electrocatalysts. This study advances the ORR, OER, and nitrate reduction reaction (NO 3 RR) technologies through a multifunctional non‐precious metal catalyst–a cobalt, sulfur, and nitrogen co‐doped carbon composite (Co, S, N‐C) synthesized via a surfactant‐assisted method. The catalyst exhibits excellent bifunctional ORR/OER activity, with a half‐wave potential of 0.818 V versus reversible hydrogen electrode for ORR and an overpotential of 431 mV at 10 mA cm −2 for OER. When integrated into a zinc–air battery as the air cathode, it delivers a peak power density of 82.5 mW cm −2 and demonstrates stable cycling performance over 100 h, with a negligible voltage gap increase of only 0.04 V. For NO 3 RR, the catalyst achieves a high NH 3 production rate of 552.1 μmol h −1 cm −2 and a Faradaic efficiency of 94.2% after 1 h of electrolysis in 0.1 M KNO 3 and 0.5 M K 2 SO 4 electrolyte. These results highlight the potential of Co, S, N‐C as a versatile platform for sustainable energy and environmental applications.

This study reports the design, fabrication, and characterization of a novel carbon paste electrode integrated with graphene and copper oxide nanohybrid (Gr/CuONPs/CPE) for the sensitive and selective voltammetric determination of the serotonin reuptake inhibitor paroxetine (PAR). Modification of the electrode surface with Gr/CuONPs nanohybrid facilitated a more efficient electrochemical oxidation of PAR at 1.046 V in BR buffer (pH 6) based on the synergistic electrocatalytic effect of the nanohybrid components and the enhanced electroactive surface area provided by the nanostructure. The electroanalytical investigations combined with molecular orbital calculations revealed a diffusion‐controlled mechanism through oxidation of the pyrimidine nitrogen atom (N6), accompanied with the transfer of two protons/one electron. At the optimized Gr/CuONPs ratio within the nanohybrid, the cited electrode demonstrated a linear response within the PAR concentrations ranged from 0.066 to 4.939 µg mL −1 and an limit of detection value of 45.4 ng mL −1 . The Gr/CuONPs/CPE exhibited extended storage stability with excellent fabrication and electrochemical measurement reproducibility. Based on the environmental impact of PAR, the developed voltammetric procedure was effectively applied for monitoring of PAR residues in surface water samples and marketed formulations with acceptable recoveries. The green analytical metrics (Analytical Eco‐Scale and Analytical GrEEness metric approach) were evaluated, highlighting the method's environmental friendliness of the suggested voltammetric procedures.

Rapid and reliable detection of Escherichia coli ( E. coli ) in water is critical for safeguarding public health. We developed a dual‐mode biosensor that integrates p‐benzoquinone (BQ)‐mediated colorimetric prescreening with antibody‐based electrochemical quantification using screen‐printed gold electrodes (SPGEs). BQ serves a dual role by generating a visible color change through its enzymatic reduction by viable E. coli and by participating in a reversible redox cycle that enhances faradaic response during electrochemical analysis. The biosensing platform was validated using E. coli ATCC 25922 together with broad‐serotype polyclonal anti‐ E. coli O/K antibodies, which enable species‐level recognition. Under optimized conditions (6.0 mM BQ, 25 µg/mL antibody), the sensor achieved a wide linear range from 10 1 to 10 9 CFU/mL with a detection limit of 0.57 CFU/mL. Repeatability was excellent (1.51% RSD), and specificity tests demonstrated clear discrimination between viable E. coli , nontarget bacteria ( S. aureus ), and nonviable cells. This dual‐selectivity strategy, combining metabolic activity with molecular recognition, offers a rapid and portable approach for on‐site microbial water quality monitoring.

Herein, we report the preparation of a new and highly efficient photoelectrocatalyst for electrocatalitic oxidation of methanol in acidic media. To this end, a fluorine‐tin oxide (FTO) electrode derived from commercial FTO plates was modified layer by layer with graphene oxide (GO) and titanium dioxide (TiO 2 ), and decorated with platinum‐osmium nanoparticles (Pt‐OsNPs) through co‐electrodeposition technique. GO nanosheets and TiO 2 nanoparticles not only served as signal amplifier and photoactive material, respectively, but also, they provided a high surface area for electrodeposition of Pt‐OsNPs. The scanning electron microscopy (SEM) images and energy dispersive X‐ray spectroscopy (EDS) spectra revealed the change of the FTO surface in each modification step. The photo electrocatalytic activity of Pt‐Os/TiO 2 /GO/FTO for methanol oxidation was assessed under visible light irradiation, and an anodic peak current density of about 10 mA cm −2 was obtained at 0.75 V. The chronoamperometry measurements showed the improved durability of Pt‐Os/TiO 2 /GO/FTO photocatalyst compared to other studied catalysts including Pt/FTO, Pt/GO/FTO, and Pt/TiO 2 /GO/FTO. The values of exchange current density ( J 0 ) obtained from Tofel plots for studied catalysts indicted that the methanol oxidation reaction is less limited kinetically in the presence of Pt‐Os/TiO 2 /GO/FTO photocatalyst.

In this work, an amperometric pyruvate‐sensitive biosensor was developed and optimized. A platinum disk electrode was used as an amperometric transducer. The bioselective element of the biosensor is based on the pyruvate oxidase enzyme immobilized with PVA‐SbQ polymer by photopolymerization. The optimal immobilization conditions (enzyme and photopolymer concentrations, duration, and intensity of photopolymerization) were selected. The optimal concentrations of cofactors and cosubstrates (phosphate ions, thiamine pyrophosphate, and magnesium ions (Mg 2+ ) were chosen to ensure the best sensitivity of the developed biosensor to pyruvate. After optimizing the design of the bioselective element and the immobilization process, the reproducibility of the biosensor manufacturing procedure was investigated (RSD = 12.5%). To assess the prospects of the developed biosensor, its main analytical characteristics were analyzed. The linear range of the biosensor was from 10 to 500 μM pyruvate, and the sensitivity was 66 nA/mM. The minimum detection threshold was 1.57 μM pyruvate. The obtained data indicate the technical feasibility and prospects of using the developed biosensor for determining the concentration of pyruvate in real multicomponent biological samples.

In this study, we evaluated the preparation conditions, stability, and durability of 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO)‐modified glassy carbon (GC) electrodes prepared using electrolytic polymerization in an aqueous solvent, and examined the applicability of the electrodes as electrochemical sensors for pharmaceutical analysis. First, we synthesized a TEMPO‐substituted phenol (2‐PH‐TEMPO) and examined the conditions for its efficient immobilization on an electrode using the electrolytic polymerization method in an aqueous solvent. The TEMPO‐modified GC electrode showed high stability and durability in a low‐concentration substrate environment and effectively functioned as an electrolytic oxidation catalyst for ethanol, a compound with a hydroxyl group. In an analysis of pharmaceuticals, a high oxidative response was obtained for lidocaine, clarithromycin, and azithromycin, which have tertiary amines or multiple oxidizable hydroxyl groups, suggesting that the electrode can function as a highly sensitive electrochemical sensor. The use of this modified electrode enables quantification in the clinical concentration range of vancomycin, and it is expected to be applied to rapid and accurate pharmaceutical concentration measurements in therapeutic drug monitoring. These results suggest that TEMPO‐modified GC electrodes are useful as stable and sensitive electrochemical sensors in the fields of pharmaceutical analysis and biosensors, and are expected to contribute to the development of quantitative electrochemical methods.

The applicability of adsorptive stripping voltammetry with hanging mercury drop electrode (HMDE) electrode has been studied for the determination of the ionic form of Ti(IV) in samples requiring specific pretreatment and decomposition of the organic matrix before measurement. Application of the mixture of conc. HNO 3 and conc. HCl (3:4) for sample decomposition in a closed microwave system using two‐stage program with a maximum temperature 210°C, and next dilution in solution preventing hydrolysis, containing 0.05 mmol L −1 KClO 3 and 0.24 mmol L −1 mandelic acid in deionized water (supporting electrolyte) allows to determine single ng of Ti(IV) in the plant leaves extract and fertilizer containing significant amounts of inorganic salts, surface compounds, and chelates. Determination was done after short deposition ( t d = 60–90s, E d = −0.150 V) with negative‐going potential scan. The method was validated by the recovery study of Ti at the ng level (complete recovery – 102%).