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Hydrogen evolution reaction on low loading iridium/graphene catalysts: structure–activity relationship
No full textIridium (Ir) is a highly active and corrosion resistant catalyst for the hydrogen evolution reaction (HER) in acidic environments. However, its high cost and limited availability necessitate strategies that reduce Ir usage while maintaining or enhancing catalytic performance. This study explores the structure–activity relationship of Ir nanoparticles supported on graphene nanoplatelets (Ir/GNPs) to develop efficient, low Ir loading HER catalysts. Ir/GNP electrodes were fabricated by electrochemical deposition from aqueous Ir precursor solutions under optimized conditions, yielding highly dispersed nanoparticles with loadings as low as 1 At%. Scanning electron microscopy (SEM) revealed that the Ir nanoparticles are uniformly distributed along the edges and defect sites of the GNP sheets, with sizes ranging from 20 to 30 nm. X-ray photoelectron spectroscopy (XPS) was employed to probe the surface chemical state of Ir and its interaction with the graphene support. The XPS results indicated the presence of metallic Ir0 along with a small fraction of Ir3+/Ir4+, suggesting partial surface oxidation and possible electronic interactions with the GNP substrate, which may contribute to enhanced catalytic behavior. Electrochemical measurements were performed in 0.5 M H2SO4 using linear sweep voltammetry. The Ir/GNP catalysts demonstrated excellent HER performance, with low overpotentials and favorable Tafel slopes, outperforming commercial Pt/C catalysts under identical conditions at similar mass loadings of noble metals. This superior activity is attributed to the synergistic effects between Ir nanoparticles and the graphene support, which provides high conductivity, abundant active sites at sheet edges, and strong metal–support interactions that optimize electron transfer and catalytic turnover. These results highlight the critical role of nanoscale morphology and surface chemistry in governing HER activity and demonstrate the potential of Ir/GNP composites as cost-effective alternatives to commercial Pt-based catalysts for hydrogen production in acidic media
Thermal stability and leaching behavior of alkali-activated slag doped with electric arc furnace dust
No full textThe study presented in this paper explores the simultaneous valorization of electric arc furnace slag (EAFS) and electric arc furnace dust (EAFD) through an alkali activation process, as well as the thermal stability of the resulting product. Moreover, environmental fingerprints of alkali activated slag doped with EAFD, before and after thermal treatment, were evaluated. The results demonstrated the feasible alkali activation of EAFS in the presence of EAFD yielding a product that met the criteria which enables its application in a civil engineering at ambient and at elevated temperatures (1000ºC). Moreover, the EN12457-2 leaching test results, demonstrated that unheated alkali-activated slag with addition of 5% EAFD met the criteria for disposal at non-hazardous landfills as per European Directive 2003/33/CE. However, environmental fingerprints of alkali activated slag with 5% EAFD after heating to 1000°C, is of concern since chromium release exceeded the permissible concentration requiring disposal in hazardous waste landfills.У овом раду испитивана је могућност валоризације електропећне троске
(ЕЛПТ) и електропећне прашине (ЕЛПП) кроз процес алкалне активације, као и
термичкa стабилност добијеног производа. Осим тога испитиванa је и еколошка
прихватљивост алкално активиране троске допиране са ЕЛПП, пре и после
термичког третмана. Резултати су показали да је алклална активације ЕЛПТ у
присуству ЕЛПП изводљива при чему се добија производ који испуњава критеријуме
који омогућавају његову примену у грађевинарству при амбијенталним и повишеним
температурама (1000 ºС). Штавише, резултати теста излужења (ЕН12457-2) су
показали да незагрејана алкално активирана троске са додатком 5% ЕЛПП испуњава
критеријуме за одлагање на неопаснoj депонији према Европској директиви
2003/33/CE. Међутим, алкално активирана троска са 5% ЕЛПП након загревања на
1000 ºС, није еколошки прихватљива јер је излужење хрома премашило дозвољену
концентрацију, што захтева њено одлагање на депонији опасног отпада
Nutritional quality, functional properties and in vitro digestibility of protein concentrates from hull-less pumpkin (Cucurbita pepo L.) leaves
No full textNutritional parameters, functional properties and in vitro protein digestibility of pumpkin (Cucurbita pepo L.) leaf protein concentrates were studied. Protein concentrates were recovered with the step of enzyme-assisted extraction or without it. Results revealed that highest level of bioavailability, essential amino acids and nutritional index were obtained for leaf protein concentrates recovered with assistance of Viscozyme and from conventional protocol. The protein concentrate extracted with the assistance of Cellulase complex exhibited the highest in vitro protein digestibility (88 %). Regarding the functionality of concentrates, highest water (3.50 g/g) and oil binding capacities (6.73 g/g), as well as solubility (96 %) have been obtained for the protein concentrate gained with the assistance of Enzyme complex. These findings indicate that pumpkin leaf concentrates can be valuable candidates for improving the nutritional profile of the food products and useful ingredients in food applications
Crystallographic and quantum chemical insight into the self-assembly and chemical reactivity of 1-benzoyl-1,3-diazaspiro[4.4]nonane-2,4-dione
No full textA cyclopentane-5-spirohydantoin bearing a benzoyl group in position N1 was synthesized and its crystal structure was determined. The intermolecular interactions in the crystal packing were firstly investigated by Hirshfeld surface analysis. A detailed quantitative description is further provided through an analysis of dimeric motifs representing various recognition modes in the solid state. Non-covalent interactions (NCI) were analyzed using the NCI descriptor based on the reduced density gradient (RDG) to visualize non-covalent attractive and repulsive interactions within selected dimeric motifs. The crystal packing is dominated by chains running along the a axis, where the molecules are linked together by N3–H3⋯O3 hydrogen bonds. The molecular electrostatic potential (MEP) surface map revealed that the N3–H3 group is an electrophilic center. When compared to a structurally-related spirohydantoin bearing the benzoyl group in position N3, the title molecule exhibits a greater number of maxima on the MEP surface of the hydantoin ring. The global reactivity descriptors indicate that the position of the aromatic substituent directly affects the kinetic stability of the molecule. Introduction of the benzoyl group at the N3 position, between two carbonyl groups of the hydantoin ring, leads to higher chemical reactivity, while introduction on the N1 atom, adjacent to only one carbonyl group, enhances the kinetic stability of the compound
Hericium erinaceus ethanol extract exhibits potent DNA-protective and antioxidant action: Evidence from in vitro and Drosophila melanogaster studies
No full textLion's mane (Hericium erinaceus (Bull.: Fr.) Pers.) is a highly valued edible fungus recognized for its diverse health benefits. This study investigated the in vitro DNA-protective effects and in vivo genotoxicity and antioxidant activity of an ethanol extract from the fruiting bodies of cultivated H. erinaceus (HEEE) using a Drosophila model. HEEE exhibited remarkable, concentration-dependent protection against DNA damage induced by hydroxyl and peroxyl radicals in vitro reaching optimal protection at 400 μg mL−1, without showing genotoxic effects in third instar Drosophila melanogaster larvae, at tested concentrations below 20 mg mL−1. HEEE displayed significant in vivo antioxidant activity under oxidative stress conditions at concentrations up to 2.5 mg mL−1. In the range of 1.25–10 mg mL−1, HEEE reduced malondialdehyde levels, while a concentration of 40 mg mL−1 exhibited a significant pro-oxidant effect. At 1.25 mg mL−1, superoxide dismutase and catalase activities increased by 23.1% and 10.6%, respectively. The concentrations of 10, 20, and 40 mg mL−1 significantly reduced superoxide dismutase activity, by 44.1%, 52.0%, and 66.4%, respectively. The concentrations of 10, 20, and 40 mg mL−1 induced an increase in glutathione (GSH) levels of 131.5%, 145.8%, and 228.7%, respectively. Quantitative Nuclear Magnetic Resonance (qNMR) spectroscopy revealed the presence of hericenes and hericenones and allowed to quantify, for the first time directly without prior separation steps, these active ingredients at 0.43% (w/w), expressed as the relative content of hericenone C. Phenolics hericenes and hericenones C–H likely contribute to the observed antioxidant and DNA-protective activities. These findings suggest that HEEE could be a valuable dietary supplement providing protection against oxidative DNA damage and supporting antioxidant defenses
Abilities of the Newly Introduced Apple Cultivars (Malus × domestica Borkh.) ‘Eden’ and ‘Fryd’ to Promote Pollen Tube Growth and Fruit Set with Different Combinations of Pollinations
No full textApple production in Western Norway faces challenges due to climatic constraints and varying phenology. It is essential for cultivars to adapt to regional ecological factors, while suitable pollinators are necessary for successful cultivation. This study examined the reproductive biology of two newly introduced apple cultivars, ‘Eden’ (Wursixo) and ‘Fryd’ (Wuranda), over two years (2022–2023). Key qualitative and quantitative parameters of reproductive biology were analyzed, including in vitro pollen germination, pollen tube growth within the style and ovary locules, flowering overlap time, and fruit set. The study involved cross-pollination between the pollen recipient cultivars ‘Eden’ and ‘Fryd’, with various pollenizers: ‘Rubinstep’, ‘Red Aroma’, ‘Elstar’, ‘Asfari’ and ‘Professor Sprenger’, as well as self-pollination and open pollination. According to the results from the progamic phase of fertilization and fruit set, the cultivars ‘Rubinstep’, ‘Asfari’, and ‘Fryd’ were the best pollenizers for ‘Eden’. In contrast, ‘Rubinstep’, ‘Eden’, and ‘Elstar’ were the best pollenizers for ‘Fryd’. Looking only at the overlapping of the flowering time between pollen recipient and pollen donor, ‘Professor Sprenger’ and ‘Fryd’ were the best pollenizers for ‘Eden’, while ‘Professor Sprenger’ and ‘Eden’ were good pollenizers for ‘Fryd’
Electrical properties of x(0.75 Na1/2Bi1/2TiO3-0.25SrTiO3)(1-x)PVDF flexible piezoceramic polymer composites
No full textInvestigations of lead-free piezoelectric materials for applications in self-powered devices rapidly increased in the last years. Herein, as lead-free piezoelectric material, we employed a system that contains sodium bismuth titanate and strontium titanate, 0.75Na1/2Bi1/2TiO3-0.25SrTiO3 (NBT-ST), which was prepared by solid-state reaction. Flexible composite films were prepared by mixing this piezoelectric material with polyvinylidene fluoride (PVDF) in different ratios and employing the hot pressing procedure. X-ray analysis confirmed the crystalline structure of the obtained NBT-ST piezoelectric phase. FTIR analysis of the flexible composite films indicated that the transformation of the electro-inactive PVDF α-phase into the electro-active β and γ phases was obtained by hot pressing. Calculated storage energy densities of the investigated films revealed an increasing trend with increasing amount of NBT-ST active phase. The same increasing trend was noticed during the testing by force impact. The highest output voltage was obtained for the samples with the highest amount of piezoelectric active phase. These flexible composite films proved significant capabilities for energy storage application, with storage efficiency up to 61 %. Moreover, the output voltage up to 18 V indicates the potential of these materials for energy harvesting applications
Полумешани вмрежени хидрогелови базирани на поли(метакрилна киселина) и природни полимери желатин, хитозан и алгинат за потенцијална биомедицинска примена
No full textHydrogels, known for their high hydration, porosity, and permeability, are widely studied for biomedical
applications. This paper reports on semi-interpenetrating network (IPN) hydrogels composed of poly(methacrylic acid)
(PMA) and natural polymers (gelatin, alginate, and chitosan), synthesized via thermally-induced free-radical
polymerization. The resulting hydrogels were evaluated for their physicochemical, mechanical, and drug release
properties. Characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, Field emission
scanning electron microscope (FE-SEM), and swelling capacity analysis, demonstrated effective integration of natural
polymers within the PMA network and their impact on hydrogel performance. PMA's pH sensitivity, combined with
natural polymers, supports its suitability for controlled drug delivery and tissue engineering. Mechanical testing showed
that adding 40 wt% of gelatin significantly increased the compressive strength from 0.16 MPa in pristine PMA to 2.35
MPa for PMA/gelatin IPN hydrogel and increased the modulus from 0.006 to 0.027 MPa. Chitosan provided moderate
mechanical improvements, while alginate showed limited effects at higher concentrations. Swelling analysis revealed
that the addition of gelatin and alginate reduced the equilibrium swelling ratio (ESR), suggesting denser crosslinking
within the hydrogel matrix. Due to its pH-sensitive properties, chitosan had increased ESR at lower pH levels, showing
potential for enhanced drug release modulation. Ciprofloxacin release studies demonstrated ESR-dependent drug
release kinetics. These findings suggest that the incorporation of natural polymers, particularly gelatin, optimizes
mechanical properties, pH-responsive swelling, and biocompatibility, making these hydrogels promising candidates for
controlled drug delivery and tissue engineering applications.Хидрогеловите, познати по нивната висока хидратација, порозност и пропустливост, се широко
проучувани за биомедицинска примена. Овој труд прикажува полумешани вмрежени хидрогелови (IPN)
составени од поли(метакрилна киселина) (PMA) и природни полимери (желатин, алгинат и хитозан),
синтетизирани преку термички индуцирана полимеризација со слободни радикали. Добиените хидрогелови беа
оценети според нивните физичкохемиски, механички и својства за ослободување на лекови. Карактеризацијата,
вклучувајќи Фурјеова трансформациска инфрацрвена (FTIR) спектроскопија, скенирачка електронска
микроскопија со емисија на поле (FE-SEM) и анализа на способноста за набабрување, покажа ефикасна
интеграција на природните полимери во мрежата на PMA и нивното влијание врз перформансите на
хидрогеловите. pH-чувствителноста на PMA, во комбинација со природните полимери, ја потврдува нејзината
погодност за контролирано ослободување на лекови и за инженерство на ткива. Механичките тестирања
покажаа дека додавањето на 40 % масен удел на желатин значително ја зголемува компресивната цврстина од
0,16 MPa кај чиста PMA на 2,35 MPa кај PMA/желатин IPN хидрогелот, како и модулот од 0,006 на 0,027 MPa.
Хитозан покажа умерено механичко подобрување, додека алгинат имаше ограничено влијание при повисоки
концентрации. Анализата на набабрувањето откри дека додавањето на желатин и алгинат го намалува
рамнотежниот коефициент на набабрување (ESR), што укажува на погуста вмреженост во матрицата на
хидрогелот. Поради своите pH-чувствителни својства, хитозанот покажа зголемен ESR при пониски pH
вредности, што укажува на потенцијал за подобра модулација на ослободувањето на лекови. Истражувањата за
ослободување на ципрофлоксацин покажаа дека кинетиката на ослободување на лекот зависи од ESR. Овие
наоди укажуваат дека вклучувањето на природни полимери, особено желатин, ги оптимизира механичките
својства, pH-одговорното набабрување и биокомпатибилноста, со што овие хидрогелови се потенцијални
кандидати за контролирано ослободување на лекови и за примена во инженерство на ткива
High-entropy aluminate spinel oxides: A pathway to advanced functional materials
No full textThis study investigates the synthesis and characterization of high-entropy aluminate spinel oxides (Al-HESOs) with three distinct compositions: (Co,Mn,Ni,Zn,Cu)Al2O4, (Co,Mn,Ni,Zn)Al2O4, and (Co,Mn,Ni,Mg)Al2O4. Using the self-propagating room temperature method for synthesis and spark plasma sintering for densification, single-phased Al-HESOs with relative densities up to 97 % were successfully obtained. Structural, mechanical, and thermal properties were comprehensively analysed, demonstrating significant tunability. Notably, the inclusion of Cu2+ drastically reduced the Young's modulus (3.8 GPa) while maintaining high hardness (9.9 GPa) and low thermal diffusivity (0.78 mm² s⁻¹ at room temperature – 0.63 mm² s⁻¹ at 600 °C), positioning (Co,Mn,Ni,Zn,Cu)Al₂O₄ as a promising candidate for strain-compliant thermal barrier coatings. These findings establish a novel synthesis and densification route for Al-HESOs and their potential for applications in advanced energy, sensing, and thermal management technologies
Mechanical Properties of the Bio-Composites: Effect of Kraft Lignin and Flax Fabric to Camphoric Acid Based Unsaturated Polyester Resin's Reinforcement
No full textThe development of the technology for bio-based resin and related composites production has nowadays become a key focus in
materials research. In line with that, in this study, the effect of the structure of camphoric acid (Cf
A) based unsaturated polyester resin (Cf
-UPR) on the mechano-chemical properties of related Cf
-UPR/Kf
L composites, produced at 5–20wt.% of Kraft
lignin (Kf
L) addition, was examined. Camphoric acid, along with bio-based maleic anhydride (MA) and propylene glycol (PG),
was used in the synthesis of the Cf
-UPR designed to enhance the wetting power of Kf
L providing improvement in mechanical
properties and thermal stability of the composites. The structure of Cf
-UPR was proved using FTIR and NMR techniques. The
morphological and mechanical properties of Cf
-UPR/Kf
L composites were studied using FE-SEM, TEM, TGA, DTA, micro indentation, and tensile test measurements. The tensile strength and toughness increase, compared to pure Cf
-UPR, for 23.9% and
93.4% at 5wt.% Kf
L addition in Cf
-UPR, respectively, while at higher Kf
L addition the values gradually decrease. The maximum
increase in microhardness, 33.1%, was recorded with the addition of the 5wt.% Kf
L. Furthermore, the tensile strength of the flax
fabric-reinforced laminated composite (Cf
-UPR/Ff) increased by an impressive 481%, which corroborates the idea about future
consideration of sustainable production of high-performance bio-based composites. By using renewable resources and minimizing environmental impact, this method not only improves the material's performance but also complies with green chemistry
principles. These composites are suitable for use in construction materials, automobile parts, and other sectors looking for environmentally friendly substitutes