Yavuz, Emre; Dundar, Ozan Ali; Yavuz, Sevtap Caglar; Yilmaz, Erkan; Ozdokur, Kemal Volkan; Cirak, Burcu Bozkurt; Caglar, Bulent; Cirak, Cagri; Arar, Özgür

Introduction: Transition metal oxides are highly effective for dye removal due to their adaptable surface chemistry, availability, and robust mechanical and thermal properties. Among them, Bi4V2O11 nanosheets offer potential due to their morphology and high surface area. To synthesize Bi4V2O11 nanosheets and evaluate their performance in removing malachite green, focusing on the impact of adsorbent amount, contact time, and interfering ions on dye removal efficiency. This study aims to evaluate the performance of Bi4V2O11 nanosheets in removing malachite green dye from aqueous solutions and to examine the effects of adsorbent dosage, contact time, and the presence of coexisting ions on the sorption process. Methods: Bi4V2O11 nanosheets were synthesized and used to remove the malachite green dye. Batch experiments were conducted to study the effects of adsorbent dose, contact time, and coexisting ions (Na+, Ca2+, and tannic acid). Equilibrium data were fitted to the Langmuir isotherm model to determine the maximum sorption capacity. Results: Malachite green sorption using Bi4V2O11 nanosheets reached equilibrium within 240 minutes, demonstrating efficient dye removal under the tested conditions. The sorption process conformed to the Langmuir isotherm model, indicating monolayer adsorption with a maximum capacity of 47.27 mg/g. While the presence of Na+ and tannic acid had negligible effects on dye removal efficiency, the coexistence of Ca2+ significantly reduced the removal efficiency from 95% to 58%, highlighting the potential impact of divalent ions on the adsorption process. Discussion: Bi4V2O11 nanosheets are effective adsorbents for malachite green removal, demonstrating high sorption capacity and resilience to Na+ and tannic acid interference. However, the presence of Ca2+ significantly reduces removal efficiency, highlighting the need for further optimization in practical applications. Conclusion: Bi4V2O11 nanosheets offer high sorption capacity and structural stability, environment friendly synthesis procedure, making them feasible for small-scale or pre-treatment applications. 2026, Bentham Science Publishers

Kaya, Lutfi; Coldur, Fatih; Kanberoglu, Gulsah Saydan

Background: The most common use of cysteamine is the treatment of cystinosis. Excessive intake of cysteamine can lead to serious side effects and health complications. Therefore, the monitoring of cysteamine levels is highly significant. Objective: Several techniques have been developed to measure cysteamine accurately. Many of these methods are constrained by various limitations, including labor-intensive pre-treatment procedures, sophisticated equipment, skilled operators, and costly consumables. The present study aims to fabricate a cysteamine-selective potentiometric sensor based on HKUST-1 metal-organic framework exhibiting a wider linear range and more sensitive potentiometric responses compared to the ion pair-based cysteamine-selective sensor that was developed previously. Methods: A novel PVC membrane cysteamine-selective sensor was fabricated by coating the membrane cocktail consisting of poly(vinyl chloride), HKUST-1 metal-organic framework, plasticizer (o-nitrophenyloctylether), and ionic additive (potassium tetrakis (4-chlorophenyl) borate) onto the conductive solid contact surface. The potentiometric performance characteristics of the sensor were evaluated in detail. Results: The sensor exhibits a linear response to cysteamine concentration in the range of 1.0×10−6 M -1.0×10−2 M (R2=0.9958) with a slope of 51.5 mV/decade and a detection limit of 8.0×10-7 M. It operates effectively within a pH range of 3.9-5.7 and displays a rapid response time. Conclusion: Compared to the cysteamine-selective sensor available in the literature, the current sensor stands out with its wider linear operating range and lower detection limit. The sensor consistently yields reproducible and stable potentiometric responses towards cysteamine. The fabricated cysteamine-selective sensor effectively quantifies cysteamine content in pharmaceutical formulations. 2026, Bentham Science Publishers

Özdokur, Kemal V.; Kuşcu, Ceren; Ertaş, Fatma N.

Background: Nowadays, polymeric composites modified with carbonaceous nanomaterials have been popular due to their greater application potentials in many application fields. However, the structural consistency of the composite prepared by electropolymerization suffers from agglomeration of Carbon Nanotubes (CNTs) probably due to their poor dispersion in the coating solution. Present study describes a new synthesis route for the preparation of polypyrrole/CNT composite film on a Glassy Carbon Electrode (GCE) via combining the ultrasonication and electrochemical pulsed deposition for the first time. The performance of the composite film was tested by monitoring the electrochemical oxidation of droxidopa which is used as a new psychoactive drug and synthetic amino acid precursor which acts as a prodrug to the neurotransmitters. Methods: The polypyrrole/CNT composite film was deposited onto a glassy carbon electrode via combining the ultrasonication and electrochemical pulsed deposition. The composite film was characterized by Scanning Electron Microscopy (SEM), Fourier Transfer Infrared Spectroscopy (FTIR), Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). Then after, the electrochemical behavior of droxidopa was investigated on the GCE/PPy-CNT electrode. Results: SEM images of the surface morphology have revealed a more ordered film formation and enhanced conductivity of the surface has been confirmed by EIS measurements. The synergetic effect of this composite film was tested by monitoring the electrochemical oxidation of a new psychoactive drug; droxidopa at 0.45 V. The influence of solution parameters such as medium pH, pyrrole concentration and amount of CNT along with the instrumental parameters including applied pulse number on the peak formation was investigated by aid of cyclic voltammetry. Under the optimal conditions, by monitoring the oxidation peak in dp mode, two linear ranges have been observed in 4 - 20 µM which is well suited for droxidopa analysis in pharmaceutical preparations. The limit of detection (S/N=3) was calculated as 1.3 µM. Conclusion: Present study offers a fast, easy and sensitive method for the determination of droxidopa by providing a novel route for the preparation of PPy-CNT composite films for any further studies.