Vinča Institute of Nuclear Sciences
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Hydrogen evolution on Ir nanoparticles supported by glassy carbon and graphene nanoplatelets
No full textThis study reports on the electrocatalytic activity of Ir nanoparticles (NPs) supported by glassy carbon (GC) and graphene nanoplatelets (GNPs) for the hydrogen evolution reaction (HER) in an acid solution. Ir/GC and Ir/GNPs catalysts were obtained by the electrochemical deposition of Ir on the two supports under the same conditions. SEM imaging revealed small, barely visible, Ir NPs highly dispersed on GC and located mainly on the edges of graphene plates on GNPs support. According to XPS analysis, the amount of the deposited Ir was 1.3 at% (15.9 wt%) in Ir/GC and 1.4 at% (16.5 wt%) in Ir/GNPs. Ir/GNPs catalyst has shown a higher HER activity, and potential for 10 mA/cm2 of −0.064 V, compared to −0.073 V for Ir/GC. The 32 mV/dec Tafel slope for Ir/GC and 38 mV/dec for Ir/GNPs indicate the Volmer-Tafel and Volmer-Heyrovski reaction pathways, respectively
Determination of antibacterial and photothermal properties of novel composites based on graphene oxide/reduced graphene oxide, gold nanoparticles, and graphene quantum dots
No full textPathogenic bacteria have emerged as a worldwide health problem nowadays as a result of excessive use or misuse of antibiotics. Thus the prevention of bacteria-mediated infections through the development of novel antibacterial materials has received significant importance. Here, we combined graphene-based materials, namely graphene oxide (GO) and reduced graphene oxide (rGO), with gold nanoparticles and modified graphene quantum dots to obtain improved composite materials. Also, we measured their light-to-heat conversion under an 808 nm laser illumination and their ability to generate singlet oxygen under photoexcitation. We determined their antibacterial properties against 8 bacterial strains. The composite of rGO showed slightly improved photothermal conversion compared to the GO counterpart due to its larger sp2 domains, while the GO composite showed the highest capacity to generate 1O2 under blue-light photoexcitation. All prepared composites had the minimum inhibitory concentrations in the range of 125 μg mL−1 to 500 μg mL−1 and did not show any cytotoxicity against MRC-5 cells. © 2025 Elsevier Ltd and Techna Group S.r.l
The baryonic Tully-Fisher relation and Fundamental Plane in the light of f(R) gravity
No full textHere we use the samples of spiral and elliptical galaxies, in order to investigate theoretically some of their properties and to test the empirical relations, in the light of modified gravities. We show that the baryonic Tully-Fisher relation can be described in the light of f (R) gravity, without introducing the dark matter. Also, it is possible to explain the features of fundamental plane of elliptical galaxies without the dark matter hypothesis. © (2025), (Astronomical Institute, Slovak Academy of Sciences). All rights reserved
受皮肤启发具有抗菌和促血管生成能力的导电水凝胶用于加速糖尿病伤口愈合
No full textIntense bacterial infection, long-term inflammatory infiltration, and inadequate vascularization make diabetic wounds non-healing. Endogenous electric fields are the basis of bioelectric signal conduction and have been shown to be the primary signal guiding cell migration and promoting tissue repair. Still, the disorder microenvironment of diabetic wounds may affect the functions of endogenous electric fields. Traditional wound dressings, such as gauzes and bandages, lead to unsatisfactory repair due to their limited infection management and inability to couple with endogenous electrical fields. In this study, we develop the PMQG hydrogel, a multifunctional hydrogel dressing with effective antibacterial properties and good electroactivity, made from acrylic acid, quaternary ammonium chitosan, and MXene nanosheets. Inspired by skin, the PMQG hydrogels have flexible mechanical properties matched to the skin, strong tissue adhesion, broad-spectrum antibacterial activity, and desirable conductivity, which could transmit electrical signals, facilitating cell migration, and thus promoting the process of wound repair. The PMQG hydrogels exhibited good antibacterial properties against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and methicillin-resistant S. aureus (MRSA), effectively controlling the infection-induced inflammation. Furthermore, incorporating MXene nanosheets into the hydrogel network enhances its reactive oxygen species scavenging ability and provides biomimetic conductivity. These anti-inflammatory properties, combined with its conductivity, help regulate the microenvironment and rebuild the endogenous electric fields, facilitating cell migration, angiogenesis, and collagen deposition, leading to a remarkable 98% wound closure by day 15 in diabetic rats, thus demonstrating superior efficacy. This novel wound dressing is expected to be an ideal therapeutic strategy for diabetic wound healing. © Science China Press 2025
Contracciones de tipo Paired-Chatterjea sincronizada: nuevos resultados de punto fijo y propiedades de continuidad en espacios métricos
No full textIntroduction/purpose: The paper deals with Paired-Chatterjea type contraction mappings as an extension of traditional Chatterjea type contractions that operates on three points rather than two, in the framework of standard metric spaces. Methods: The concept of Chatterjea type contraction mappings is employed in a metric space on three points rather than two using the idea of paired contraction mappings. Results: A series of corresponding properties has been discussed. Furthermore, it is established that Paired-Chatterjea type mappings form a distinct class from traditional Chatterjea type mappings and obtain at least one fixed point in the absence periodic points of prime period 2 within complete metric spaces. It is also demonstrated that how additional criteria to these mappings, such as continuity and asymptotic regularity, broaden the scope of fixed point results. Extending beyond Chatterjea’s foundational contributions, two additional fixed point results applicable to Paired-Chatterjea type mappings in metric spaces are established, even in scenarios where completeness is not required. Conclusions: Paired-Chatterjea type mappings are generally discontinuous; they exhibit continuity at fixed points similar to Kannan and Chatterjea type mappings. In the absence of a periodic point of prime period 2, these mappings have a fixed point within the complete metric space. © 2025 The Authors
A Biomimetic Approach to Diode Laser Use in Endodontic Treatment of Immature Teeth: Thermal, Structural, and Biological Analysis
No full textThe root walls of immature permanent teeth are often weak, thin, and short, making regenerative endodontic treatment (RET) necessary. The goal of RET is to create a favorable environment for further root development. A biomimetic approach is essential for thorough disinfection, followed by the preservation and potential stimulation of stem cells from surrounding tissue to enable root regeneration and continued development. The objective of this study was to assess temperature changes on the external root surface, structural alterations in the internal root walls following irradiation with a 940 nm diode laser, and the biocompatibility of stem cells from the apical papilla (SCAPs). Irradiation was performed with varying output powers (0.5 W, 1 W, 1.5 W, and 2 W) in continuous mode for 5 s over four consecutive cycles. Thermographic measurements during irradiation, the micro-CT analysis of root samples, and mitochondrial activity of SCAPs were evaluated. The heating effect correlated directly with a higher output power and thinner root walls. A 1 W output power was found to be safe for immature teeth, particularly in the apical third of the root, while 1.5 W could be safely used for mature mandibular incisors. Diode laser irradiation at 1 W and 1.5 W significantly stimulated SCAPs’ mitochondrial activity within 24 h post-irradiation, indicating a potential photobiostimulatory effect. However, no significant changes were observed at lower (0.5 W) and higher (2 W) output powers. The area of open tubular space inside the root canal was significantly reduced after irradiation, regardless of the applied power. Additionally, irradiation contributed to the demineralization of the dentin on the inner root walls. Future studies should explore the impact of irrigants used between irradiation cycles, the potential benefits of conical laser tips for more even energy distribution, and a thorough analysis of how disinfection protocols affect both the dentin structure and stem cell viability. © 2025 by the authors
Degradation of Microplastics by Plasma, UV Radiation, and Ozone: FTIR and Raman Spectroscopic Analysis of Polystyrene, Polyethylene, and Polypropylene
No full textAdvanced Ceramics and Application : 13th Serbian Ceramic Society Conference : Program and the Book of Abstracts; September 8-10, 2025; Belgrade
Method for Degradation of Colored Eluents After Desorption From Chemically Functionalized Cellulosic Material
No full textIn this study, a method for the removal and degradation of colored eluents after desorption from chemically functionalized cellulosic materials was developed. Waste hemp fibers were transformed into an efficient cellulosic adsorbent through a two-step process involving delignification and subsequent quaternization with betaine hydrochloride-urea. The fibers were first subjected to delignification, followed by quaternization using the synthesized deep eutectic solvents (DES), betaine hydrochloride- urea. The adsorbent was evaluated for the removal of anionic dyes, including Metanil Yellow (MY) and Congo Red (CR), in a batch adsorption system. Structural and chemical characterization of the modified fibers was performed using Scanning Electron Microscopy (SEM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), porosity measurements, and point of zero charge (pHpzc) analysis. Pore size was determined through image analysis and the dry-wet weight method. The adsorption process was found to be endothermic and spontaneous, achieving high adsorption capacities (qm) at 25°C, with the optimal pH for adsorption being 7. Kinetic studies indicated that the adsorption followed both pseudo-first-order (PFO) and pseudo-second-order (PSO) models. After adsorption, the desorbed dyes were subjected to photocatalytic degradation using zinc oxide as a catalyst, with high and rapid decolorization efficiency, particularly for Metanil Yellow. The photocatalytic process ensured that the treated water posed minimal environmental risk. This work demonstrates the application of green chemistry principles in the functionalization of waste lignocellulosic materials and the subsequent degradation of colored eluents, offering an eco-friendly and efficient method for water purification and wastewater treatment.Materials, Methods & Technologies : 27th International Conference; 14-17 August 2025; Burgas, Bulgaria
Sustainable Valorization of Conifer Cones: A Potent Source of Antioxidants and Bioactive Compounds
No full textIntroduction: Antioxidants are critical in mitigating oxidative stress-related diseases and play a fundamental role in industrial applications by inhibiting oxidation, rancidity, and degradation, thereby enhancing product stability and quality. The identification of waste biomass with potent antioxidant properties and a high concentration of biologically active compounds is essential for the sustainable utilization of natural resources. Such biomass- derived antioxidants offer a promising, environmentally sustainable alternative to their synthetic counterparts, contributing to both human health and industrial sustainability. Experimental: In this study, the optimization of microwave-assisted extraction (MAE) parameters for the recovery of bioactive compounds from mature Pinus nigra and Thuja orientalis cones, a lignocellulosic waste produced in large quantities, with insufficiently explored biological potential, was conducted. The extraction process was carried out under constant microwave power, while ethanol concentration (as the extraction solvent), solid-to-liquid ratio, and extraction duration were systematically varied. The resulting extracts were evaluated for their antioxidant activity using the TPTZ (ferric reducing antioxidant power) and DPPH (2,2-diphenyl-1- picrylhydrazyl) assays. Furthermore, the extracts were characterized for their total phenolic content (TPC), as well as total flavonoids, hydrolyzable tannins, and terpenoids, along with their dry matter (DM) content. Results: The results demonstrated that antioxidant activity and bioactive compound content increased with the intensification of extraction parameters up to a critical threshold, beyond which a decline was observed. The optimal extraction conditions included a microwave power of 90 W, an ethanol concentration of 40%, an extraction time of 60 seconds, and a biomass-to-solvent ratio of 1:40 (w/v). Mature P. nigra cones extract exhibited the highest antioxidant activity, as determined by the FRAP assay (3.1629 mmol Fe2+/g DM), which was further confirmed by the DPPH method. Additionally, mature P. nigra cones extract contained higher total phenolic content (328.1226 mg GAE/g DM) and total flavonoid content (62.0985 mg QE/g DM), while mature T. orientalis cones extract exhibited a higher content of hydrolyzable tannins (1.6321 mg GAE/g DM) and total terpenoids (8.0391 mg LIN/g DM). This study demonstrates the innovative potential of mature pine cones by revealing their relatively high content of key bioactive compounds and strong antioxidant activity. The research follows sustainable principles by optimizing mild extraction conditions, avoiding toxic solvents, and minimizing energy consumption. Moreover, the proven presence of bioactive compounds encourages further investigation into additional biological activities, such as anti-inflammatory and anti-diabetic effects, expanding the potential utilization of this natural resource.International Conference "Biobased Future: Green Bioprocessing for Innovative Bioactive Products" ; June 16-18, 2025; Belgrade
Functionalized Fe3O4 Nanoparticles for Stable Immobilization of Horseradish Peroxidase
No full textIntroduction: Horseradish peroxidase (HRP) is a widely used enzyme in industrial and analytical applications due to its high catalytic efficiency and substrate specificity. However, its practical application is often limited by poor stability and the inability to be reused. Enzyme immobilization on solid supports presents a promising strategy to enhance enzyme stability, reusability, and operational efficiency. This study is dedicated to developing a stable and efficient biocatalyst by immobilizing horseradish peroxidase (HRP) onto magnetite (Fe₃O₄) nanoparticles functionalized with specific organic ligands. The functionalization strategy aims to improve enzyme- support interactions, thereby increasing immobilization efficiency and maintaining enzymatic activity over multiple usage cycles. The effect of ligand type on catalytic activity retention and overall biocatalyst performance was systematically investigated under varying experimental conditions. Experimental: Fe₃O₄ nanoparticles were synthesized via a standard co- precipitation method using ferrous and ferric salts in an alkaline medium. The surface of the synthesized nanoparticles was then functionalized with two ligands: caffeic acid (containing a free carboxyl group) and 5- aminosalicylic acid (containing a free amino group). These ligands were selected based on their potential to form stable interactions with enzyme molecules through electrostatic attraction or covalent bonding. The immobilization of HRP onto the functionalized nanoparticles was carried out under controlled conditions, with variations in enzyme concentration and the quantity of the carrier material. The pyrogallol assay was used to evaluate enzymatic activity after immobilization, where horseradish peroxidase (HRP) catalyzes the oxidation of pyrogallol in the presence of hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the absorbance at 420 nm at 30-second intervals. The operational stability and reusability of the immobilized enzyme were evaluated over multiple catalytic cycles. Key findings: The functionalization of Fe₃O₄ nanoparticles significantly influenced immobilization efficiency and enzymatic performance. Materials modified with 5-aminosalicylic acid exhibited excellent retention of peroxidase activity over five consecutive cycles, with only a minor decrease in catalytic efficiency. This suggests that amino groups on the nanoparticle surface promote stable enzyme binding and favorable orientation for catalysis. In contrast, nanoparticles functionalized with caffeic acid, which contains a carboxyl group, showed a marked decline in activity as early as the second usage cycle. This reduction is attributed to weaker enzyme-carrier interactions at the working pH of 8.5, likely due to the pKa values of the ligand affecting charge distribution and binding affinity. These findings demonstrate the critical role of surface chemistry in enzyme immobilization and highlight the importance of tailoring functional groups to optimize biocatalyst stability and performance. The results contribute to the broader understanding of how ligand selection can be used to design efficient and reusable nanostructured enzyme carriers for various industrial and biomedical applications.International Conference "Biobased Future: Green Bioprocessing for Innovative Bioactive Products" ; June 16-18, 2025; Belgrade