Search Results (79)

A pyranochromene-based ligand, 2-amino-4-(4-chlorophenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (ACLPh-PC-3-CN), was employed as a chelating modifier for the electrochemical determination of Cd(II) in water samples. ACLPh-PC-3-CN was co-immobilized with Nafion on a glassy carbon electrode to form a stable ACLPh-PC-3-CN/Nafion film that combines ligand-based coordination with cation-exchange-assisted preconcentration of Cd²⁺ at the electrode surface. The Cd(II) response at the modified electrode was characterized by cyclic voltammetry and differential pulse anodic stripping voltammetry, and the data support a predominantly 1:1 Cd(II)–ligand interaction at the interface under the selected conditions. At an optimized pH of 6.0, the sensor provided a linear calibration range from 16.21 to 56.72 μM, with a detection limit of 0.60 μM and a quantification limit of 2.0 μM, and showed good precision (repeatability 2.3% RSD, reproducibility 3.1% RSD) and short-term stability (94% of the initial response after 14 days). The ACLPh-PC-3-CN/Nafion-modified electrode tolerated common inorganic ions and surfactant species (≤5% signal change) and was successfully applied to the determination of Cd(II) in tap water and Red Sea water, affording recoveries between 98.7% and 101%. While the current detection limit is higher than typical guideline values for Cd in drinking water, the proposed sensor compares favorably with several reported electrochemical Cd(II) sensors in terms of simplicity, precision, and matrix tolerance, and represents a useful platform for coordination-based electrochemical sensing of cadmium in environmental water samples. Full article

The photoelectrochemical water-splitting process for hydrogen production is limited by the large bandgap of semiconductor titanium dioxide (TiO₂) and by interfacial recombination at particle interfaces. The technique used in this paper is that of electrochemical anodization to produce robust, ordered TiO₂ nanotube arrays (TiO₂ nanorod arrays denoted as TNTAs). Using the immersion-annealing method, Nd₂O₃ nanoparticles can be immobilized in situ, and Nd₂O₃/TNTAs composite photoanodes are fabricated. The heterointerface caused between the Nd₂O₃ nanoparticles and TiO₂ results in the alignment of the Fermi levels and the formation of band bending and an internal electric field at the interface. It allows rapid photo-generated electron-hole (e⁻/h⁺) separation at the interface and, simultaneously, introduces novel localized electron states of Nd³⁺ within the TiO₂ bandgap. This triggers hybridisation between the 3d orbitals of Ti and the 2p orbitals of O, thereby altering the band structure of TiO₂. The best-performing Nd₂O₃/TNTAs photoelectrode outperforms pure TNTAs, with a photocurrent density of 1.59 mA·cm⁻² at 1.23 V vs. RHE. It produces 162.6 μmol·cm⁻² of hydrogen in a 3 h photocatalytic hydrogen production experiment, which is about 12.2 times that of pure TNTAs. This approach highlights the unique benefits and creative opportunities of applying rare-earth elements to address the critical issues of photocatalysts, such as significant band gaps and rapid recombination. Full article

Modified electrodes were obtained by immobilizing Mn³⁺ complexes with the following tetraazamacrocycles (1,4,7,10-tetraazacyclododecane ([12]aneN₄), 1,4,8,11-tetrazacyclotetradecane ([14]aneN₄), 1,4,7,11-tetrazacyclotetradecane (iso[14]aneN₄), and 1,4,8,12-tetrazacyclopentadecane ([15]aneN₄) in a Nafion film on the surface of a glassy carbon electrode (GCE). Based on spectroelectrochemical, chronopotentiometric, and chronoamperometric studies, oxidation of mononuclear complexes to dinuclear di-μ-oxo complexes of Mn³⁺ and Mn⁴⁺ was observed, and the mechanism and influence of Nafion on this process were determined. On the basis of voltammetric and chronocoulometric studies, the electroactivity, stability, and diffusion rates of such modified electrodes were demonstrated. Based on voltammetric and chronocoulometric studies, their electrocatalytic properties were analyzed in relation to the oxidation of model compounds used in this type of research, namely, ascorbic acid, glycolaldehyde, and glycolic acid. Full article

This study aims to develop an innovative electrochemical genosensor based on activated biochar (ABC) derived from the biomass of the seaweed Sargassum spp. The synthesis process begins with the pyrolysis of Sargassum spp. at 500 °C to obtain biochar (BC), which is chemically activated with nitric acid (HNO₃). The physicochemical properties of the resulting material, such as morphology and surface area, were characterized using techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and the Brunauer–Emmett–Teller (BET) method for surface area. BET results showed an increase in surface area from 22.9367 ± 0.0879 m²/g (BC) to 159.2915 ± 2.2641 m²/g (ABC). For the development of the genosensor, a hydrolyzed collagen gel matrix enriched with ABC is created. This nanostructured, biocompatible mixture is used to immobilize a DNA probe on a graphite electrode, employing the large surface area of ABC and the formation of a functional HC-based coating. The system’s viability was evaluated by cyclic voltammetry (CV), which showed changes in the maximum anodic peak current (Ipa) during fabrication: 27.78 ± 1.87 μA for the bare electrode, 35.25 ± 1.24 μA for ABC 30%, and 39.25 ± 1.84 μA for HC + ABC 30%. After ssDNA immobilization and hybridization to dsDNA, Ipa decreased to 28.81 ± 1.565 μA and 23.10 ± 1.25 μA, respectively. Finally, hematoxylin (Hx) was used as an intercalating indicator from hybridization, reducing the maximum anodic peak current to 15.51 ± 1.13 μA, consistent with additional interfacial limitations associated with dsDNA formation. Overall, the developed system demonstrates a sustainable, promising platform for molecular diagnostics in electrochemical DNA biosensor development. Full article

Herein, we propose an ultrasensitive electrochemical immunosensor based on glucose oxidase labeling and enzyme-catalyzed Au staining. In brief, the primary antibody (Ab₁), bovine serum albumin, an antigen and then a bionanocomposite that contains a second antibody (Ab₂), poly(3-anilineboronic acid) (PABA), Au nanoparticles (AuNPs) and glucose oxidase (GOx) are modified on a glassy carbon electrode coated with multiwalled carbon nanotubes, yielding a corresponding sandwich-type immunoelectrode. In the presence of glucose, a chemical reduction of NaAuCl₄ by enzymatically generated H₂O₂ can precipitate a lot of gold on the Ab₂-PABA-AuNPs-GOx immobilized immunoelectrode. In situ anodic stripping voltammetry (ASV) detection of gold in 8 μL 1.0 M aqueous HBr-Br₂ is conducted for the antigen assay, and the ASV detection process takes approximately 6 min. This method is employed for the assay of human immunoglobulin G (IgG) and human carbohydrate antigen 125 (CA125), which demonstrates exceptional sensitivity, high selectivity and fewer required reagents/samples. The achieved limits of detection (S/N = 3) by the method are 0.25 fg mL⁻¹ for IgG (approximately equivalent to containing 1 IgG molecule in the 1 microlitre of the analytical solution) and 0.1 nU mL⁻¹ for CA125, which outperforms many previously reported results. Full article

The transition toward sustainable and decentralized energy solutions necessitates the development of innovative bioelectronic systems capable of harvesting and converting renewable energy. Here, we present a novel photo-bioelectrochemical fuel cell architecture based on a biohybrid anode integrating laser-induced graphene (LIG), poly(3,4-ethylenedioxythiophene) (PEDOT), and isolated thylakoid membranes. LIG provided a porous, conductive scaffold, while PEDOT enhanced electrode compatibility, electrical conductivity, and operational stability. Compared to MXene-based systems that involve complex, multi-step synthesis, PEDOT offers a cost-effective and scalable alternative for bioelectrode fabrication. Thylakoid membranes were immobilized onto the PEDOT-modified LIG surface to enable light-driven electron generation. Electrochemical characterization revealed enhanced redox activity following PEDOT modification and stable photocurrent generation under light illumination, achieving a photocurrent density of approximately 18 µA cm⁻². The assembled photo-bioelectrochemical fuel cell employing a gas diffusion platinum cathode demonstrated an open-circuit voltage of 0.57 V and a peak power density of 36 µW cm⁻² in 0.1 M citrate buffer (pH 5.5) under light conditions. Furthermore, the integration of a charge pump circuit successfully boosted the harvested voltage to drive a low-power light-emitting diode, showcasing the practical viability of the system. This work highlights the potential of combining biological photosystems with conductive nanomaterials for the development of self-powered, light-driven bioelectronic devices. Full article

Amperometric biosensors (ABSs) and enzymatic biofuel cells (BFCs) share several fundamental principles in their functionality, despite serving different primary purposes. Both devices rely on biorecognition, redox reactions, electron transfer (ET), and advanced electrode materials, including innovative nanomaterials (NMs). ABSs and BFCs, utilizing microbial oxidoreductases in combination with electroactive NMs, are both efficient and cost-effective. In the current study, several laboratory prototypes of BFCs have been developed with bioanodes based on yeast flavocytochrome b₂ (Fcb₂) and alcohol oxidase (AO), and a cathode based on fungal laccase. For the first time, BFCs have been developed featuring anodes based on Fcb₂ co-immobilized with redox NMs on a glassy carbon electrode (GCE), and cathode-utilizing laccase combined with gold–cerium–platinum nanoparticles (nAuCePt). The most effective lactate BFC, which contains gold–hexacyanoferrate (AuHCF), exhibited a specific power density of 1.8 µW/cm². A series of BFCs were developed with an AO-containing anode and a laccase/nAuCePt/GCE cathode. The optimal configuration featured a bioanode architecture of AO/nCoPtCu/GCE, achieving a specific power density of 3.2 µW/cm². The constructed BFCs were tested using lactate-containing food product samples as fuels. Full article

In an enzyme-based fuel cell system, glucose oxidase and laccase were immobilized on carbon paper as the anode and cathode electrodes. A conductive polymer (polypyrrole) was added to improve conductivity. The mediator and enzymes were mixed in a phosphate-buffer solution for entrapment. A Nafion 212 membrane separated the two half-cells. Power density measurements were taken at a glucose concentration of 10 mM across different operating voltages. Potassium hexacyanoferrate III was used as a redox mediator in the anode and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) in the cathode to boost power output. The biofuel cells, constructed from acrylic (40 × 50 × 50 mm) with a working volume of 20 × 30 × 40 mm, were assembled using a rubber gasket to secure the Nafion membrane. The use of micropore tape covering the electrodes extended the system’s operational lifespan. Without the micropore tape, the maximum power density was 57.6 μW/cm² at 0.24 V. With the micropore tape, the cell achieved a maximum power density of 324.9 μW/cm² at 0.57 V, sustaining performance for 20 days. Thus, micropore tape effectively enhances enzyme retention and biofuel cell performance. Full article

COVID-19 antibody detection is dependent on highly specialized, time-consuming techniques, such as PCR separation, DNA amplification, and other methods such as spectrophotometric absorption. For these reasons, specialized technical training is necessary because individual diagnostic treatment is difficult. We have attempted to perform rapid sensing with a detection time of only 30 s. Additionally, we used a wearable multi-layer graphene oxide nanocolloid synthetic skin tattoo probe assay for influenza and COVID-19 virus detection with an electrochemical antigen–antibody redox ionic titration circuit. Cyclic voltametric−2 V~2.0 V potential windows were used. The diagnostic detection limit was determined using stripping anodic and cathodic amplifiers, and the working probe was fabricated with a graphene molecule structure with a virus antigen-immobilized amplifier. With redox potential strength obtained within −1.0 V~−1.3 V ionic activity, anodic and cathodic current linearly increased in the phosphate-buffered saline 5 mL electrolyte. The results indicate that instant detection was enabled via individual and wearable tattoo sensors. Full article

The WHO has classified Helicobacter pylori as a group 1 carcinogen for stomach cancer since early 1994. However, despite the high prevalence of Helicobacter pylori infection, only about 3% of infected people eventually develop gastric cancer.Biomolecular detections of Helicobacter pylori(HP) were compared using specially modified sensors and fluorine immobilized on a carbon nanotube (HFCNT) electrode, which yielded sensitive results. Handheld voltammetric circuits were used for optimization. An anodic voltammogram of HP molecular oxidation was obtained at 0.0 V ± 0.1 (versus the Ag/AgCl/KCl) in a 0.1 ± 0.2 M NH₄H₂PO₄ electrolyte solution. Under optimized conditions, the analytical working range was 2.98 × 10³–22.127 × 10⁻³ CFU/mL HP using square wave (SW) stripping voltammetry, precision of R² = 0.9857 ± 0.0005 (SWSV), the detection limit approached to 2.5 × 10² CFU/mL HP (S/N = 3).The developed techniques have been applied to diagnosis of early-stage HP infections using stomach tissue from healthy humans and gastric patients. Full article

This study explores the adsorption of Pb(II) from aqueous solutions using glutathione-modified carbon powder at room temperature. The graphite powder was modified through oxidation followed by surface immobilization of glutathione. The Pb(II) concentration was measured using square wave anodic stripping voltammetry (SWASV). Experiments were conducted with the following varying initial Pb(II) ion concentrations: 20.72 mg L⁻¹, 41.44 mg L⁻¹, 62.16 mg L⁻¹, 82.88 mg L⁻¹, 103.60 mg L⁻¹, and 124.32 mg L⁻¹. The effect of varying the glutathione-modified carbon powder dosage (12.5 mg, 25.0 mg, 50.0 mg, 75.0 mg, and 100.0 mg) on Pb(II) uptake was studied. The adsorption data were modeled using the Freundlich isotherm, resulting in a regression coefficient (R²) of 0.96, which signifies a good fit. The Freundlich constants obtained were K_F = 3.54 × 10⁻⁵ (adsorption capacity) and n = 1.56 (adsorption intensity). At optimal conditions (10.0 mL of 20.72 mg L⁻¹ Pb(II) solution with 100.0 mg of glutathione-modified carbon powder), the adsorption efficiency was 96.3%. The glutathione-modified carbon powder exhibits a high capacity for adsorbing Pb(II) from aqueous solutions. Full article

The selection of an appropriate transducer is a key element in biosensor development. Currently, a wide variety of substrates and working electrode materials utilizing different fabrication techniques are used in the field of biosensors. In the frame of this study, the following three specific material configurations with gold-finish layers were investigated regarding their efficacy to be used as electrochemical (EC) biosensors: (I) a silicone-based sensor substrate with a layer configuration of 50 nm SiO/50 nm SiN/100 nm Au/30–50 nm WTi/140 nm SiO/bulk Si); (II) polyethylene naphthalate (PEN) with a gold inkjet-printed layer; and (III) polyethylene terephthalate (PET) with a screen-printed gold layer. Electrodes were characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to evaluate their performance as electrochemical transducers in an aptamer-based biosensor for the detection of cardiac troponin I using the redox molecule hexacyanoferrade/hexacyaniferrade (K3[Fe (CN)6]/K4[Fe (CN)6]. Baseline signals were obtained from clean electrodes after a specific cleaning procedure and after functionalization with the thiolate cardiac troponin I aptamers “Tro4” and “Tro6”. With the goal of improving the PEN-based and PET-based performance, sintered PEN-based samples and PET-based samples with a carbon or silver layer under the gold were studied. The effect of a high number of immobilized aptamers will be tested in further work using the PEN-based sample. In this study, the charge-transfer resistance (Rct), anodic peak height (I_pa), cathodic peak height (I_pc) and peak separation (∆E) were determined. The PEN-based electrodes demonstrated better biosensor properties such as lower initial Rct values, a greater change in Rct after the immobilization of the Tro4 aptamer on its surface, higher I_pc and I_pa values and lower ∆E, which correlated with a higher number of immobilized aptamers compared with the other two types of samples functionalized using the same procedure. Full article

The bacterial anode of microbial electrolysis cells (MECs) is the limiting factor in a high hydrogen evolution reaction (HER). This study focused on improving biofilm attachment to a carbon-cloth anode using an alginate hydrogel. In addition, the modified bioanode was encapsulated by a filter bag that served as a physical barrier, to overcome its low mechanical strength and alginate degradation by certain bacterial species in wastewater. The MEC based on an encapsulated alginate bioanode (alginate bioanode encapsulated by a filter bag) was compared with three controls: an MEC based on a bare bioanode (non-immobilized bioanode), an alginate bioanode, and an encapsulated bioanode (bioanode encapsulated by a filter bag). At the beginning of the operation, the Rct value for the encapsulated alginate bioanode was 240.2 Ω, which decreased over time and dropped to 9.8 Ω after three weeks of operation when the Geobacter medium was used as the carbon source. When the MECs were fed with wastewater, the encapsulated alginate bioanode led to the highest current density of 9.21 ± 0.16 A·m⁻² (at 0.4 V), which was 20%, 95%, and 180% higher, compared to the alginate bioanode, bare bioanode, and encapsulated bioanode, respectively. In addition, the encapsulated alginate bioanode led to the highest reduction currents of (4.14 A·m⁻²) and HER of 0.39 m³·m⁻³·d⁻¹. The relative bacterial distribution of Geobacter was 79%. The COD removal by all the bioanodes was between 62% and 88%. The findings of this study demonstrate that the MEC based on the encapsulated alginate bioanode exhibited notably higher bio-electroactivity compared to both bare, alginate bioanode, and an encapsulated bioanode. We hypothesize that this improvement in electron transfer rate is attributed to the preservation and the biofilm on the anode material using alginate hydrogel which was inserted into a filter bag. Full article

Li-N₂ batteries present a relatively novel approach to N₂ immobilization, and an advanced N₂/Li₃N cycling method is introduced in this study. The low operating overpotential of metal–air batteries is quite favorable to their stable cycling performance, providing a prospect for the development of a new type of battery with extreme voltage. The battery system of Li-N₂ uses N₂ as the positive electrode, lithium metal as the negative electrode, and a conductive medium containing soluble lithium salts as the electrolyte. In accordance with its voltage-distribution trend, a variety of lithium-nitrogen molecule intermediates are produced during the discharge process. There is a lack of theoretical description of material changes at the microscopic level during the discharge process. In this paper, the first-principles approach is used to simulate and analyze possible material changes during the discharge process of Li-N₂ batteries. The discharge process is simulated on a 4N-graphene anode substrate model, and simulations of its electrostatic potential, Density of States (DOS), HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) aspects confirm that the experimentally found Li₃N becomes the final stabilized product of the Li-N₂ battery. It can also be seen in the density of states that graphene with adsorption of 4N transforms from semiconducting to metallic properties. In addition, the differential charge also indicates that the Li-N₂ material has a strong adsorption effect on the substrate, which can play the dual role of electricity storage and nitrogen fixation. Full article

The bacterial anode in microbial fuel cells was modified by increasing the biofilm’s adhesion to the anode material using kaolin and graphite nanoparticles. The MFCs were inoculated with G. sulfurreducens, kaolin (12.5 g·L⁻¹), and three different concentrations of graphite (0.25, 1.25, and 2.5 g·L⁻¹). The modified anode with the graphite nanoparticles (1.25 g·L⁻¹) showed the highest electroactivity and biofilm viability. A potential of 0.59, 0.45, and 0.23 V and a power density of 0.54 W·m⁻², 0.3 W·m⁻², and 0.2 W·m⁻² were obtained by the MFCs based on kaolin–graphite nanoparticles, kaolin, and bare anodes, respectively. The kaolin–graphite anode exhibited the highest Coulombic efficiency (21%) compared with the kaolin (17%) and the bare (14%) anodes. Scanning electron microscopy and confocal laser scanning microscopy revealed a large amount of biofilm on the kaolin–graphite anode. We assume that the graphite nanoparticles increased the charge transfer between the bacteria that are in the biofilm and are far from the anode material. The addition of kaolin and graphite nanoparticles increased the attachment of several bacteria. Thus, for MFCs that are fed with wastewater, the modified anode should be prepared with a pure culture of G. sulfurreducens before adding wastewater that includes non-exoelectrogenic bacteria. Full article