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Comparative analysis of in-situ ionic activators for increased energy efficiency process in alkaline electrolysers
No full textElectrodeposition of selected d-metals by in-situ electrodeposition as a method for improvement of electrocatalytic activity of conventional electrodes for alkaline hydrogen evolution has been attracting the attention of researchers for about two decades. The modification of metal electrodes by ionic activators as a combination of two (binary systems) or three (ternary systems) d-metal complexes added in electrolytic solution were represented in many studies. Better catalytic performances and higher energy efficiency compared to the common electrodes is provided by a number of affordable and inexpensive solutions resulting from this research. Based on the combinations of selected d-metal complexes added in-situ to the electrolyte during electrolysis, this work provides a systematic overview of the binary and ternary systems of ionic activators, that contribute to energy savings in alkaline electrolysers, with the particular attention paid to the discussion of similarities and universal principles. Theoretical background and the fundamental properties that lay beyond the observed improvements of electrode performance upon activation by ionic activators is also represented.Elektrodepozicija prelaznih metala putem in situ jonske aktivacije, koja dovodi do povećanja elektrokatalitičke aktivnosti i veće energetske efikasnosti konvencionalnih elektroda kod alkalnih elektrolizera, jeste predmet istraživanja već dugi niz godina. Dvokomponentni i trokomponentni in situ jonski aktivatori predstavljaju izabranu kombinaciju dva ili tri d-metala u obliku kompleksa, jednostavno dodatih u elektrolit. Ovaj rad predstavlja sveobuhvatan pregled svih dvokomponentnih i trokomponentnih sistema koji su ispitivani za in situ poboljšanje katalitičkih performansi metalnih elektroda i povećanje energetske efikasnosti alkalne elektrolize vode. Posebna pažnja je posvećena komparativnoj analizi različitih jonskih aktivatora sa naglaskom na sličnosti i univerzalne principe, kao i uporednoj primeni teorijskih i eksperimentalnih metoda u ispitivanju ovakvih sistema
Preparation of magnetic fluids based on La0.80Ag0.15MnO3-δ nanoparticles
No full textWater-based magnetic fluids were prepared using La0.80Ag0.15MnO3-δ magnetic carriers with the maximal Curie temperature TC = 319.5 K (46.4 °C). The starting nanoparticles mainly consisted from agglomerates with average particle size between 43 and 47 nm. Separation of nanoparticles from aggregates using a stirred ball mill in combination with the use of anionic sodium dodecyl sulphate surfactant led to the preparation of electrostatically stabilised magnetic fluid with average hydrodynamic size of particles xav less than 75 nm. A combination of mechanical grinding, sonication and etching in different acids was used to prepare Dextran 40 kDa sterically and carboxymethyl-dextran 15 kDa electrosterically stabilised magnetic fluid with average hydrodynamic size of particles ranging between 50 and 190 nm. Milling and etching results in reduction of TC of about 3 K, etching causes a drastic decrease in saturation magnetization, but the magnetocaloric properties are unaffected by the preparation of the magnetic fluid, only the magnetic entropy change is reduced by three orders of magnitude. Magnetic carrier has the potential to reach the desired magnetic heating temperature T = 43.6 °C for applications in hyperthermia and magnetic fluids are capable to reach T = 38.1 °C by magnetic heating. The maximal specific absorption rate of magnetic carrier SAR = 134.7 W/g and in the case of magnetic fluid SAR = 41.9 W/g. The synthesized nanoparticles and the prepared magnetic fluids may represent materials with potential in cancer treatment, as the most pronounced effect was observed in the case of lung cancer cell line A549. Analysed nanoparticles induced a decrease in metabolic activity even at relatively low concentrations. © 2025 Elsevier B.V
The luminescence of Mn4+ in K2GeF6
No full textIn this work, we report on the spectroscopic properties of Mn4+ in the fluoride host, K2GeF6. The Mn4+ luminescence intensity and lifetime are measured as a function of temperature. From the data, we have determined the onset temperature and activation energy for thermal quenching of luminescence. The optical properties and thermal quenching behavior of Mn4+ in K2GeF6 are compared with those reported for commercial Na2SiF6:Mn4+ and K2SiF6:Mn4+ (TriGain®) phosphors. This comparative study sheds light on the mechanism of thermal quenching of the Mn4+ ion luminescence in the A2XF6 (A = K, Na; X = Si, Ge) family of materials. We provide evidence that the activation energy and the onset temperature of thermal quenching for the 2E→ 4T2→ 4A2 crossover process is correlated with the energy of the 4T2 level and argue that this is a robust electronic structure-property relationship in host fluorides with low defect density. The K2GeF6 is reported to undergo structural phase transitions in the temperature ranges of 220–240 K and 150–170 K. We have probed the phase transitions by temperature dependent Raman spectroscopy. The evidence for structural phase transition in our Raman experiments is lacking. © 2025 Elsevier B.V
The Effect of Phase Changes on Optoelectronic Properties of Lead-Free CsSnI3 Perovskites
No full textFirst-principles calculations were carried out within the framework of density functional theory to investigate the influence of phase changes on the electronic and optical properties of CsSnI3. The lattice parameter and band gap of four different phases, i.e., α-, β-, γ-, and δ-phases, of CsSnI3 are estimated by employing different exchange–correlation functionals in order to explore their ability to reproduce geometric and electronic structures adequately. Comparison of the calculated total energies shows the non-perovskite orthorhombic (δ-phase) modification of CsSnI3 is the most stable, followed by the orthorhombic (γ-CsSnI3) perovskite phase. Thermal stability calculations in the form of temperature dependence of entropy as well as the absence of imaginary frequencies in the phonon dispersion diagrams also confirmed the dynamical stability of the δ-CsSnI3. The influence of the structural phase changes on the band gap and Fermi level shifts of CsSnI3 were assessed. Contribution of the electronic states on the formation of the valence and conduction band of four phases of CsSnI3 were determined, which were calculated using various exchange–correlation functionals, including the high-precision hybrid functional HSE06, and compared with available experimental ones. The calculated energy band distribution diagrams showed that all three perovskite modifications of CsSnI3 have direct transitions, while δ-CsSnI3 has an indirect transition. It was found that during the transition from δ- to α-phase, the Fermi level descends to the low energy region (towards the valence band), and the band gap decreases from 2.99 eV to 1.33 eV. During the transition from α- to β-phase, the band gap width again decreases to 1.23 eV and the Fermi level mixes by 1.65 eV towards the conduction band (CB). On the contrary, the band gap increases from β- to γ-phase and the Fermi level shifts by 0.41 eV towards the conduction band. The values of the complex dielectric constant and the refractive index of four phases of CsSnI3 were also calculated. © The Author(s) 2025
Doubling the relative sensitivity of YNbO4:Sm3+ luminescence thermometer by observing 4G7/2 emitting level
No full textThe value of the energy gap between the thermally coupled emission levels of trivalent lanthanides limits the relative sensitivities of Boltzmann-type luminescent thermometers. The values of the relative sensitivities further decrease as the temperature increases, making their use challenging at high temperatures. Here, for the first time, we used the higher-energy emitting level of Sm3+ (4G7/2) to improve the relative sensitivity at high temperatures. We prepared a YNbO4:Sm3+ (6 mol% doping) luminescence thermometry probe using a vibrational ball mill, which homogenized the precursors, and thermally treated them for solid-state reactions. X-ray diffraction measurements proved that the phosphor crystallized in a monoclinic fergusonite-beta-(Y) structure, C2/c(15) space group, with a calculated average crystallite size of 83 nm. Scanning electron microscopy revealed the polycrystalline powder, with particles of about a few tens of micrometers. Photoluminescence excitation and emission spectra were recorded at 186 K as well as at room temperature. The excited state lifetime of the 4G5/2 level measured at 300 K is 0.42 ms. The emission spectra were recorded in the 300–650 K temperature range and analyzed using the luminescence intensity ratio method. The results demonstrated a twofold increase in relative sensitivity within the 500–650 K temperature range when compared to the first excited level (4F3/2). The highest relative sensitivity at 300 K is calculated from the 4F3/2 level to be 1.81 %K−1, while in the high temperature region it reached 1.31 %K−1 at 500 K (obtained from the 4G7/2 level). © 2025 Elsevier B.V
CBRN Incidents and Critical Infrastructure: The Role of First Responders in an Integrated Emergency Management and Resilience Building in Serbia
No full textThis paper investigates the perceptions of institutional capacities, preparednessPreparedness levels, and interagency coordinationInteragency coordination among several organizations in the Republic of SerbiaSerbia (RS) responsible for responding to chemical, biological, radiological, and nuclear (CBRN) incidents. The research, based on a quantitative survey conducted with 139 professionals from four major institutions, indicates a generally developed awareness of CBRN risks and the importance of effective early response. However, the findings also reveal differences in the depth of knowledge, availability of technical resources, and implementation of standardized procedures, which appear to stem from the specific mandates and operational experiences of individual institutions. While specialized units, such as the CBRN Center and the Sector for Emergency Management, demonstrate relatively advanced capacities and readiness, other agencies—such as the Customs Administration and Border Police—express the need for additional support in terms of targeted trainingTraining and access to technical tools. Educational background and gender were also found to influence perceptions, as respondents with higher educationEducation levels and female respondents showed greater confidence in the existence of national-level CBRN response structures. Moreover, the results suggest that improving communication infrastructure and establishing mobile detection capabilities could significantly enhance the national response framework. Overall, the research emphasizes the importance of continued institutional investment in capacity-building efforts, interagency coordinationInteragency coordination mechanisms, joint trainingTraining initiatives, and the promotion of gender equality in order to further harmonize and strengthen the nationalSystem system for managing CBRN threats
Activated Carbon Derived from Plane Tree (Platanus) Fruits by Ba(OH)2 Activation and Its Possible Application as Catalyst Support in Reforming Processes: Kinetic and Thermodynamic Study of Thermal Reactivation with Mechanistic Investigation
No full textIn this study, a novel activated carbon (AC) (AC-Ba(OH)2) was synthesized through a three-step process (including hydrothermal carbonization (at 250 °C), alkali activation by Ba(OH)2, and pyrolysis (at 850 °C)), from Plane tree fruits (PTFs). By using various experimental methods for material characterization, it was established that the resulting material possesses a variety of oxygen functional groups, rich in alkaline earth oxides (BaO/CaO), SiO2, consisting of graphitized carbon with graphene structures. A detailed kinetic and thermodynamic analysis of AC-Ba(OH)2 thermal restoring was also carried out. Thermodynamic analysis revealed the existence of a true thermodynamic compensation effect (TCE) during restoration. Restoration was controlled by entropy, where experimental temperatures are above the iso-entropic temperature, i.e., the temperature where contributions of enthalpy and entropy to activation free energy are balanced. Kinetic modeling has shown that restoration allows carbon material to be significantly modified by removing oxygen-containing groups via diffusion, changing active sites on the surface, and preparing material for catalyst support. CaO and SiO2 act as catalysts, while BaO alters graphene surface properties. Isothermal prediction tests have shown an extremely high long-term stability of modified AC-Ba(OH)2, supporting an elevated activity, selectivity, and lifetime, as well. The restoring process resulted in an energy consumption of 0.762 kWh, which is equivalent to the reactivation of AC with a lower specific surface area. Manufactured AC and its thermally modified counterpart can be used as both a catalyst support and catalyst for reforming processes, such as methanol synthesis, biogas purification, and dry reforming of methane
Biocompatible gold–titanium oxide nanomotors promote ROS-driven cell death in A375 human melanoma cells
No full textLight-driven metal-oxide nanomotors are emerging as promising tools for efficient tumor penetration and intracellular drug delivery, offering enhanced antitumor activity. Titanium oxide nanomotors can overcome tumor microenvironmental barriers under light irradiation and propel themselves using tumor-derived H2O2. Their mobility improves cellular uptake and therapeutic efficacy, however, the precise mechanisms underlying their antitumor activity remain unclear. Here, we explored the cytotoxicity of newly developed gold–titanium oxide (AuTiO2) nanomotors on A375 human melanoma cells, focusing on their effects on cell viability, morphology, and cell death pathways. To assess the biological effects of AuTiO2nanomotors, cell viability was measured by MTT assay, revealing dose-dependent cytotoxicity (0.5-10 μg/ml) after 24h. Phase-contrast microscopy showed morphological changes consistent with cell death. Flow cytometry analyses confirmed apoptosis as the predominant pathway, showing increased Annexin V⁺ and Annexin V⁺/PI⁺ cells, elevated intracellular ROS detected with the ROS-sensitive dye DCFDA, and caspase involvement verified by inhibition with Apostat. Additionally, the hemolysis test showed no adverse effects on red blood cells after 3 hours of incubation, suggesting that the application of the nanomotors is unlikely to induce intravascular hemolysis, and can be further assessed for biocompatibility. Collectively, these findings demonstrate that AuTiO2 nanomotors effectively induce ROS- driven, caspase-dependent apoptosis in A375 melanoma cells while exhibiting minimal toxicity toward red blood cells. Together, the results highlight the potential of AuTiO2 nanomotors as a potent strategy for targeted anti-melanoma therapy.Twenty-Third Young Researchers' Conference Materials Science and Engineering, December 3-5, 2025, Belgrade, Serbia
Interface-engineered STO thin films on silicon photocathodes for photoelectrochemical hydrogen evolution reaction
No full textEpitaxial strontium titanate (STO) thin films were deposited by pulsed laser deposition onto bare and reduced graphene oxide (rGO)-buffered silicon (Si) substrates to explore their potential as protective and functional coatings for Si photocathodes in photoelectrochemical (PEC) hydrogen evolution reaction. Depositions were carried out at 515 ℃ and 700 ℃, and the resulting films were characterized using reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray reflectivity (XRR), and X-ray photoelectron spectroscopy (XPS). AFM and XRR analyses revealed that the STO films grown on rGO-buffered Si exhibited smoother surfaces and lower roughness compared to those grown directly on Si. XRD and RHEED methods revealed that the growth at 700 °C led to the formation of textured film, while deposition at 515 ℃ on rGO-buffered Si substrate produced highly crystalline STO film with a dominant (002) out-of-plane orientation. The sharp RHEED streaks further confirmed its high crystallinity and smoothness. Electrochemical measurments showed that epitaxial STO/rGO photocathodes achieved significantly improved PEC performance, featuring a reduced onset potential (0.24 V vs RHE), higher photocurrent density (−27.78 mA cm⁻²), and greater long-term stability. Conversely, non-epitaxial samples containing interfacial silicate or silicide layers, particularly those deposited at 700 °C, exhibited lower activity and reduced stability, as confirmed by electrochemical impendance spectroscopy (EIS). The results highlight the crucial role of interface engineering and deposition temperature in tailoring the structural and functional performance of oxide/Si heterostructures for efficient hydrogen evolution reaction.Twenty-Third Young Researchers' Conference Materials Science and Engineering, December 3-5, 2025, Belgrade, Serbia
Raman signatures of CDW induced phonon folding in TaTe4
No full textTaTe4 is a quasi-one-dimensional transition metal telluride known for its commensurate charge density wave (CDW) state and complex lattice modulation below 450 K. In low-dimensional materials, CDW is mostly driven by strong electron–phonon coupling and give rise to complex lattice distortions and collective electronic order. Despite numerous studies, the detailed crystal structure and vibrational properties associated with the CDW state in TaTe4 have yet to be fully characterized. Using polarization-resolved Raman spectroscopy in the temperature range between 100 and 300 K, we investigated the vibrational properties of TaTe4 within its commensurate CDW phase. In total, seventeen modes were observed, exceeding the ten Raman-active ones expected in the high-temperature phase. The appearance of additional modes indicates zone folding consistent with the 2a × 2a × 3c CDW superstructure. Comparison with DFT-calculated phonon energies enabled assignment of the original zone- center modes of the high-temperature structure and the additional folded modes activated by the CDW superstructure. Beyond the discrete phonon lines, a broad continuum centered around 150 cm-1 was detected and attributed to two-phonon scattering from acoustic branches activated by zone folding. These findings provide direct experimental evidence of phonon folding driven by CDW modulation and underscore the intricate coupling between electronic and lattice degrees of freedom in TaTe4. This study constitutes the first polarization-resolved Raman investigation of TaTe4, offering new insight into the symmetry and temperature evolution of folded phonons in this quasi-low-dimensional CDW system.Twenty-Third Young Researchers' Conference Materials Science and Engineering, December 3-5, 2025, Belgrade, Serbia