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Electrochemical Regeneration of 1,4-NADH: The Role of Copper Electrode Morphology in Selectivity and Efficiency
No full textBioelectrochemical systems are gaining increasing attention for their potential to revolutionize sustainable industrial processes by coupling enzymatic activity with electrochemical redox reactions. A critical challenge in these systems is the reliance on expensive cofactors, such as nicotinamide adenine dinucleotide (1,4-NADH), which are consumed upon reduction, necessitating costly continuous supplementation. To address this, researchers have explored in situ regeneration methods, with direct electrochemical regeneration emerging as a promising solution. However, key challenges remain, including poor selectivity and high overpotential, which depend heavily on catalyst properties and operating conditions. While prior studies have focused on catalyst material selection and reaction parameters, the structural and morphological characteristics of the electrode play a crucial yet underexplored role in enhancing efficiency and product selectivity.
In this work, we investigate copper-based electrodes, an environmentally and cost-effective material, for the electrochemical regeneration of 1,4-NADH. We developed a custom cell for the electrochemical deposition of copper on copper substrates, producing catalysts with varied grain sizes and morphologies. These engineered electrodes are systematically evaluated for their impact on 1,4-NADH regeneration efficiency and selectivity. Our results demonstrate that tailored copper electrode structures significantly influence reaction performance, with optimized conditions achieving high selectivity toward 1,4-NADH. Furthermore, the non-toxic and scalable nature of copper underscores its potential for sustainable electrochemical biocatalysis. This study highlights the critical role of electrode morphology in optimizing cofactor regeneration, offering a pathway toward more efficient and eco-friendly bioelectrochemical systems
Morphology Analysis of Hydrogen Evolution Reaction in the Zn-air Batteries
No full textZinc-based batteries using alkaline electrolytes include Zn-MnO2, Zn-Ni/Co, Zn-Ag, and Zn-Air batteries, and they have occupied one third of a battery market in the world. The widespread use of these batteries is related to unique characteristics of Zn, such as extraordinary theoretical capacity, low cost and low toxicity, as well as by an abundance of Zn in nature. These rechargeable batteries use Zn as an anode, and despite successful commercialization, there are still challenges in a development of this battery type. They are related with a growth of dendrites, surface passivation, shape change, and hydrogen evolution. Considering these challenges, this study aims to analyze morphological aspects of hydrogen evolution reaction as a parasitic reaction during the zinc electrodeposition from alkaline zincate electrolyte.
Electrodeposition of Zn was performed potentiostatically from 0.35 M ZnO in 6.0 M KOH at overpotentials of -160, -220, -280, and -340 mV vs. Zn. The morphology of Zn deposits was characterized by the scanning electron microscopy (SEM) technique. For the electrolyte of this composition, the plateau of the limiting diffusion current density corresponded to a range of overpotentials between -90 and -180 mV vs. Zn. After the end of this plateau, the fast and exponential growth of the current density was observed with the further increase of overpotential.
Hydrogen evolution reaction as a parasitic reaction during Zn electrodeposition, and hence the charging process, commences at overpotentials outside the plateau of the limiting diffusion current density. It is manifested by appearing of craters or holes from detached hydrogen bubbles at the surface area of the electrode. Intensification of hydrogen evolution occurs with increasing the overpotential of electrodeposition, leading to the increase of number of holes and the decrease of their diameter. The coalescence of neighboring hydrogen bubbles also occurs, and it becomes especially visible with the longer duration of the electrodeposition process, as well as at higher overpotentials. The hole size decreased from about 100 micrometers and more obtained at an overpotential of -220 mV vs. Zn to about 10 micrometers at an overpotential of -340 mV vs. Zn.
Based on the performed morphological analysis, it follows that the volume of generated hydrogen was not enough to cause an effective electrolyte stirring in the near-electrode layer and to inhibit a growth of dendrites. The well developed 2D (two dimensional) and 3D (three dimensional) dendrites were formed around the holes. A possible explanation for the absence of an inhibition of dendritic growth should look for into electrochemical parameters of Zn, i.e. to affiliation of Zn to the group of normal metals characterized by high values of both the exchange current density and overpotential for hydrogen evolution reaction
Electrochemical and Surface Insights Into X12CrMoWVNbN10‐1‐1 Steel Corrosion in Chloride Solutions at Variable pH
No full textThe corrosion behavior of X12CrMoWVNbN10‐1‐1 steel was investigated in 0.1 M NaCl solutions of different pH values (2.9,
6.5, and 10.3) using electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and potentiodynamic
polarization (PDP). A pronounced pH dependence was observed, with the highest corrosion rate and lowest polarization
resistance in acidic medium. Neutral and alkaline environments promoted passive film formation, with the alkaline solution
providing superior protection against general and pitting corrosion. The enhanced passivation is attributed to the stabilizing
role of hydroxide ions. Surface morphology by optical microscopy and SEM confirmed these trends, revealing severe deg-
radation in acid and compact surfaces in neutral and alkaline media. Quantitative comparison with reference steels (P91 and
316 L) confirms an order‐of‐magnitude improvement in corrosion resistance, emphasizing the practical relevance of
X12CrMoWVNbN10‐1‐1 for chloride‐containing environments. The results highlight its strong corrosion stability under
variable‐pH exposure
Production of xylooligosaccharides from corn cob using a novel endoglucanase A from Aspergillus tubingensis
No full textThe sustainable recovery of bioactive compounds from agro-industrial waste is crucial for developing
value-added bioproducts. This study investigated a novel enzymatic approach for producing xylooligosaccharides (XOS) from corn cob, an abundant agricultural residue. A xylanase was isolated from
the fermentation liquid of Aspergillus tubingensis grown on SSF corn cob and identified via mass spectrometry (LC-MS/MS) as Endoglucanase A, an enzyme previously unreported for xylan hydrolysis.
The enzyme exhibited remarkable activity against xylan isolated from corn cob, efficiently generating
XOS without detectable xylose formation, characteristic of GH11 endoxylanases.
The resulting XOS displayed diverse degrees of polymerisation and showed strong antioxidant activity (according to DPPH and FRAP test), suggesting their potential as functional food ingredients. This
enzymatic process provides a green and efficient alternative for XOS production, avoiding the need
for harsh chemical treatments and reducing processing costs. Moreover, the unique capability of Endoglucanase A to act on hemicellulosic substrates expands its biotechnological relevance beyond its
classical classification. Our findings highlight a new application of A. tubingensis endoglucanase A in
agro-waste valorisation and contribute to the broader goals of circular bioeconomy and sustainable
food innovation
Designing electrochemical sensor using Metal-organic frameworks: Tailored structures and response characteristics
No full textMetal-organic frameworks (MOFs) have gained significant interest due to their potential applications in catalysis, batteries, separation processes, and gas sensing (1). These materials provide an innovative approach to the modular design of functional porous substances. By modifying the arrangement of inorganic nodes—composed of metal atoms or metal-oxo clusters—and organic linkers, typically polycarboxylates, a diverse range of three-dimensional frameworks can be synthesized. These frameworks exhibit a variety of topologies, textural properties, pore accessibility, and chemical characteristics on their internal surfaces (2).
Metal-organic frameworks made from rare-earth (RE) elements—such as scandium, yttrium, and the lanthanide series—are an intriguing category known for their unique structural and functional properties. The coordination chemistry of RE metals is diverse, with only minor energetic differences among various coordination numbers and geometries, which are primarily influenced by the steric effects of ligands. Unlike d-block metals, RE metals display distinct electronic properties due to their 4f electron configurations, which are shielded from the external environment by the 5s and 5p orbitals. This shielding results in unique electronic and magnetic characteristics that are largely unaffected by coordinating ligands. By carefully adjusting the RE metal nodes and organic linkers, researchers can create RE-MOFs with complex structures and varied topologies, providing many opportunities for the development of functional materials.
In this study, we present the synthesis of various rare earth metal-organic frameworks (RE-MOFs) featuring different rare earth metals—specifically lanthanum, samarium, gadolinium, and dysprosium—along with benzene-1,3,5- tribenzoate (BTB) as the organic linker. The synthesis process commenced with the preparation of the organic linker, followed by the hydrothermal synthesis of the MOFs. The subsequent analysis focused on the influence of the metal on the structural and morphological characteristics of the synthesized MOF materials, employing techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Furthermore, the study examined the electrochemical properties of the resultant MOFs, exploring their potential
applications for the development of electrochemical sensors through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).
These findings provide valuable insights into the application of MOFs in electrochemical sensor development and highlight the efficacy of different rare earth metals in the synthesis of electrochemically advantageous MOFs.Abstract book: [https://www.euroanalysis2025.com/images/site/abstracts/ABSTRACT_EUROANALYSIS_2025.V13.pdf
Unmodified Hemp Biowaste as a Sustainable Biosorbent for Congo Red and Remazol Brilliant Blue R
No full textIndustrial hemp (Cannabis sativa L.) was investigated as a sustainable biosorbentfor removing Congo Red (CR) and Remazol Brilliant Blue R (RBBR) from wastewater. Theunmodified hemp biosorbent exhibited moderate but practically relevant sorption capacities(4.47 mg/g for CR; 2.44 mg/g for RBBR), outperforming several agricultural wastematerials. Kinetic studies revealed rapid uptake, with CR following pseudo-first-orderkinetics (t1/2 < 15 min) and RBBR fitting the Elovich model, indicating heterogeneoussurface interactions. Equilibrium data showed CR adsorption was best described by theTemkin isotherm (R2 = 0.983), while RBBR followed the Langmuir model (R2 = 0.998),reflecting their distinct binding mechanisms. Thermodynamic analysis confirmed spontaneous(ΔG◦ < 0), exothermic (ΔH◦ ≈ −2 kJ/mol), and entropy-driven processes forboth dyes. Molecular docking elucidated the structural basis for performance differences:CR’s stronger binding (−7.5 kcal/mol) involved weak noncovalent interaction arisingfrom partial overlap between the π-electron cloud of an aromatic ring and σ-bonds C-C orC-H (π-σ stacking) and hydrogen bonds with cellulose, whereas RBBR’s weaker affinity(−5.4 kcal/mol) relied on weak intermolecular interaction between a hydrogen atom (froma C-H bond) and the π-electron system of an aromatic ring (C-H···π interactions). Thiswork establishes industrial hemp as an eco-friendly alternative for dye removal, combiningrenewable sourcing with multi-mechanism adsorption capabilities suitable for small-scalewater treatment applications
Fabrication of electrochemical sensor based on Eu2O3/rGO nanostructure for endocrine disruptor estradiol sensing. Theoretical perspective on the sensing mechanism
No full textAccurate detection and monitoring of endocrine disruptor estradiol in clinical and environmental contexts are crucial due to its implications for health and ecological systems. In this work, we developed an electrochemical sensor based on europium oxide (Eu2O3) and reduced graphene oxide (rGO) for quantification of estradiol in aqueous solutions. Eu2O3 synthesized using the hydrothermal method formed ultrasmall and uniform nanoparticles and showed an efficient electrochemical behavior. Eu₂O₃ nanoparticles were incorporated with rGO and characterized by XRD, FTIR, SEM, and TEM. The obtained Eu₂O₃@rGO composite was drop-casted on the surface of a screen-printed carbon electrode to construct a sensor for estradiol quantification. The fabricated sensor exhibited an impressive limit of detection (0.06 µM) and a limit of quantification (0.236 µM), with a sensitivity of 2.44 µA µM⁻¹ cm⁻², using SWV. The obtained SWV curve shows the oxidation current increased during the addition of estradiol concentration from 0.1 to 30 µM. The practical applicability of the SPCE/Eu₂O₃@rGO sensor was demonstrated for detecting estradiol in tap water, river water, and saliva samples. The results obtained with the SPCE/Eu₂O₃@rGO sensor closely matched those from the UV–Vis validation method, confirming its reliability and accuracy. The developed sensor represents a promising candidate for routine environmental analysis due to its portability, lower cost, and potential for on-site and real-time monitoring
ZnO-nanostructured electrochemical sensor for efficient detection of glyphosate in water
No full textGlyphosate is a widely used broad-spectrum herbicide for controlling grassy weeds, despite having potential health hazards. Herein, we report on a solid-state electrochemical sensor based on ZnO nanoparticles (ZnO NPs) for on-site detection of glyphosate. Accordingly, ZnO NPs was drop-cast on the surface of a disposable screen-printed carbon electrode. Eco-friendly ZnO NPs of only 7 nm crystallite sizes were obtained by green sol-gel synthesis using lemon (Citrus limon) waste aqueous extract as the green reducing and capping/stabilizing agent and Zn nitrate precursor as evidenced by scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), X-ray diffraction and diffuse reflectance. SEM confirmed successful electrode functionalization with the synthesized nanoparticles. Under laboratory conditions in acetate buffer (pH 5), the sensor demonstrated excellent selectivity and sensitivity, with a detection limit of 0.648 μM, a wide linear detection range (0.5 μM to 7.5 mM), and a rapid detection time of 30 min. When tested in river water, the sensor achieved a detection limit of 0.96 μM using differential pulse voltammetry. It also exceptionally tolerated interference from similar organophosphorus compounds and ions commonly found in river water. The excellent detection performance of the sensor was attributed to the strong coordination interactions between Zn atoms and phosphonate/carboxylate groups that are enhanced by a hydrogen bond at acidic pH, as determined by chemical calculations. This disposable sensor offers a cost-effective, efficient, and environmentally friendly solution for monitoring glyphosate in water systems
Wearable Heart Rate Sensors Based on Laser-Induced Graphene on Alginate and Novel Polyurethanes
No full textThe rapid expansion of wearable sensor technology has raised concerns about electronic waste and
environmental sustainability. Traditional wearable sensors are often made from non-degradable
materials, contributing to long-term pollution and disposal challenges. As the demand for wearable
health monitoring devices grows, it is essential to develop biodegradable alternatives that maintain
high performance while minimizing environmental impact. In this study, we present two biodegradable
substrates for wearable sensors: a naturally derived cross-linked sodium alginate (CL-SA) film and a
novel synthetic polyurethane based on α,ω-dihydroxy-poly(ε-caprolactone)-b-poly(dimethylsiloxane)
b-poly(ε-caprolactone) (PCL-b-PDMS-b-PCL).
The alginate film was synthesized by dissolving sodium alginate in distilled water, followed by
crosslinking with Ca²⁺ ions. Laser-induced graphene (LIG) was produced on CL-SA substrates via direct
laser induction. For the polyurethane-based substrate, we synthesized a polymer network using PCL
b-PDMS-b-PCL, 4,4’-methylenediphenyl diisocyanate, and hydroxy-functional hyperbranched
polyester through a two-step polymerization. Polyurethanes with soft segment contents of 40, 50, and
60 wt% were prepared for subsequent integration with LIG.
To assess the potential of both materials for wearable sensor applications, we performed an extensive
physicochemical analysis of synthesized substrates and LIG samples on each substrate. Raman
spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray
diffraction, transmission electron microscopy, and Fourier-transform infrared spectroscopy were used
to examine the structure and composition of the prepared materials. The analysis revealed that while
CL-SA provides a biodegradable platform, the polyurethane-based network offers superior flexibility,
making it more suitable for wearable applications. Given its enhanced flexibility, we selected the
polyurethane-based LIG sensors for real-time heart rate monitoring. Utilizing the piezoresistive
properties of LIG, we recorded heartbeat signals by connecting the sensors to a pulse simulator and a
measuring device. Voltage changes were measured over time in constant current mode,
demonstrating the sensor’s ability to detect subtle physiological signals with high sensitivity.
These results highlight the potential of integrating LIG with biocompatible and biodegradable
substrates for sustainable, high-performance wearable sensors. By combining biocompatibility,
flexibility, and precise physiological detection, this work paves the way for eco-friendly, next
generation health monitoring technologies
Synthesis of novel DDSA-modified levans and comparison study of environmental and biological evaluation with OSA-modified levans
No full textHydrophobic modification of polysaccharides enhances their potential as emulsion stabilizers and encapsulating agents, but their biocompatibility and biodegradability must be assessed first. In this study levan polysaccharide was modified by dodecenyl succinic anhydride (DDSA) for the first time, and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and thermogravimetric and differential thermal analysis (TGA/DTA). The mentioned methods confirmed the grafting reaction and showed that the modification increases the roughness of the polysaccharide film, while thermostability and porosity of the levan stays preserved. Environmental behaviour and biocompatibility were compared for modified levans with a degree of substitution in the range of 0.032 to 0.048 prepared by octenyl succinic anhydride (OSA) or DDSA treatment at concentrations of 5 to 10 % (w/w). In a 28-day soil biodegradation test, the overall degradation of modified levans was in the range of 63–78 %. Modified levans at a concentration of up to 40 mg/mL had no adverse effects on A. fischeri bioluminescence. Also, in a test with a normal foetal lung fibroblast MRC-5 cell line, no cytotoxicity was measured for OSA- and DDSA-modified levans at concentrations up to 1 mg/mL