Facile construction of mechanically robust and highly osteogenic materials for bone regeneration

Hydrogel-based materials exhibit great potential in tissue engineering. However, their mechanical weakness limits applications in hard tissue regeneration, especially under load-bearing conditions. Although various strengthening strategies have been applied, the achieved mechanical response of hydrogels still lags behind the mechanics of natural bone. In this study, we present a novel mineralization approach to fabricate mechanically robust and highly osteogenic mineralized hydrogels. Cross-linking between deprotonated chains of poly(acrylic acid) (PAA) and divalent cations has led to formation of hydrogels with a compressive strength and elastic modulus of 0.3 ± 0.1 kPa and 1.3 ± 0.2 kPa, respectively. Subsequent in situ formation of nano-calcium hydroxide crystals remarkably increased the compressive strength and modulus to 7.9 ± 0.6 MPa and 339.3 ± 31.4 MPa, respectively, surpassing those of trabecular bone. Moreover, the mineralized hydrogels demonstrated remarkable osteogenic potential in vivo, exhibiting immunoregulatory activity, promoting early angiogenesis, and accelerating fracture healing at weeks 4 and 8. The mechanism of osteogenesis was further revealed by transcriptome sequencing, indicating that the mineralized hydrogels regulated the translation of extracellular matrix and biomineralization. Overall, our study presents a pioneering and cost-effective method for fabricating materials with exceptional mechanical strength and strong osteogenic properties, offering a promising avenue for load-bearing bone repair applications of hydrogel-based materials. © 2025 The Author

Electrical properties of x(0.75 Na1/2Bi1/2TiO3-0.25SrTiO3)(1-x)PVDF flexible piezoceramic polymer composites

Investigations 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. © 2025 Elsevier B.V

Experimental Investigation of the Stability of AunCln+m− (n = 1–5; m = 1, 3, 5, 7) Clusters by Laser Desorption/Ionization Mass Spectrometry

The stability of gold chloride clusters is an important topic in catalysis and nanomaterials, but experimental data are missing. Here, fourteen different clusters were obtained simultaneously using laser desorption/ionization mass spectrometry and were identified as AunCln+m − (n = 1–5; m = 1, 3, 5, 7) or AuCln+1 −, Au2Cl2n+1 −, Au3Cl2n+2 −, Au4Cl2n+1 − and Au5Cl2n+2 −. Consequently, the effects of laser intensity on their stability were evaluated, considering differences in the AuCl unit or the number of Cl atoms. For the AunCln+1 − and AunCln+3 − groups, the relative intensity of the clusters decreased with each additional AuCl unit as the laser intensity increased. AunCln+5 − clusters showed a different trend in relative intensities: Au3Cl8 − > Au2Cl7 − > Au4Cl9 − > Au5Cl10 −. The mononuclear AuCl4 − showed the highest stability, which is consistent with their “superhalogen” character. In the Au2Cl2n+1 − clusters, Au2Cl5 − with Au (III)–Au(I) interaction was more stable at lower laser intensities, while Au2Cl3 with Au(I)–Au(I) bonds became more dominant at higher intensities. Among the Au3Cl2n+2 −, Au4Cl2n+1 − clusters, those with purely “aurophilic” interactions became increasingly stable with increasing laser intensity. These results emphasize the importance of bond type and cluster size for the stability of gold chloride clusters at different laser intensities

Nitrogen-doped graphene quantum dot-aromatic amino acid hybrids: synthesis, interface interactions, and photoluminescence properties

Nitrogen-doped graphene quantum dots (NGQDs) were synthesized through a straightforward and rapid hydrothermal method using citric acid and urea as precursors. The resulting NGQDs were non-covalently functionalized (conjugated) with aromatic amino acids, specifically phenylalanine (Phe) and tryptophan (Trp). Atomic force microscopy analysis revealed that the NGQDs exhibit a disk-like morphology, with an average diameter of approximately 60 nm and an average height of around 0.4 nm. Following conjugation, the height of the particles increased to approximately 3 nm. UV-vis spectroscopy confirmed the successful conjugation of the amino acids to the NGQD nanostructures. Density functional theory (DFT) numerical calculations were conducted using three different N-doped clusters to further investigate the nature of the non-covalent interactions between NGQDs and the respective amino acids. Photoluminescence spectra demonstrated stable and intense fluorescence signals for both hybrids in the UV region. The most significant changes were observed in the case of Trp conjugation. Unlike phenylalanine, the non-covalent bonding of tryptophan to NGQDs significantly influenced the visible emission at around 500 nm, which originates from the surface states of the quantum dots.18th Photonics Workshop : International conference; March 16-20, 2025; Kopaonik, Serbia

On compact topological edge modes in photonic ribbon lattices

Topological insulation and the associated unidirectional propagation of edge modes have opened new avenues for light control, enabling the design of novel photonic devices with enhanced performance and stability [1]. The number of topologically protected edge modes, determined via the bulk-edge correspondence, is linked to changes in the bulk k- space Hamiltonian and is quantified by topological invariants such as the winding number (Zak phase) in 1D and Chern numbers in 2D systems. This framework inherently implies a nonzero band curvature. In contrast, flatband (dispersionless) systems offer a distinct route for light control by supporting highly compact localized modes (CLMs). While topological protection and flatband localization are typically considered opposing effects, their interplay can significantly enhance the robustness of edge modes. Recent studies have demonstrated the existence of compact topologically protected modes [2,3]. Here, we systematically analyze this phenomenon in quasi-1D ribbon photonic lattices, considering four graphene-like ribbon configurations where the band curvature can be tuned by introducing an artificial magnetic flux in specific plaquettes. We investigate the emergence of compact topological edge modes in the presence of ribbon symmetries and geometric constraints. Additionally, we examine the robustness of CLMs against disorder and nonlinear effects and identify optimal lattice configurations for device design. Initial experimental efforts in realizing SP states [2], provide promising confirmation of our approach.18th Photonics Workshop : International conference; March 16-20, 2025; Kopaonik, Serbia

The Electronic Structure of Ag-Bi-S-I Nanomaterials Studied by X-ray Aerosol Photoelectron Spectroscopy

Silver-Bismuth iodide rudorffites emerged as promising lead-free, non-toxic, and chemically stable materials for photovoltaic applications. Recently, we developed two novel synthesis routes to obtain Ag-Bi-I nanoparticles [1, 2]. Motivated by a recent study that demonstrated that partial substitution of I- with S2- ions can lead to band gap modification due to upshifting the valence band maximum in the presence of sulfide anions, thereby enhancing photoconversion efficiency in solar cells, we also synthesized Ag-Bi-S-I and AgBiS2 nanoparticles. We performed synchrotron radiation X-ray aerosol photoelectron spectroscopy (XASP) to study the difference in the valence electronic structure of Ag-Bi-I, AgBiS2, and Ag- Bi-S-I nanoparticles. This technique allows for the analysis of isolated nanoparticles free from solvent and ligand molecules [4, 5]. Additionally, the use of tunable synchrotron radiation wavelengths enables the acquisition of high-resolution spectra from highly diluted systems.Advances in Solid State Physics and New Materials - 30 years of the Center for Solid State Physics and New Materials at the Institute of Physics Belgrade, 19 – 23 May 2025, Belgrade, Serbia

Microstructure, Hardness, and Wear Behavior of Layers Obtained by Electric Arc Hardfacing Processes

Hardfacing is a welding-related technique aimed at depositing a harder and tougher layer onto a softer, less wear-resistant substrate or base metal. This process enhances the abrasion resistance of the component, increasing its durability under working conditions. A key feature of hardfacing is dilution, which refers to the mixing of the hardfacing layer and the base metal. In this study, shielded metal arc welding (SMAW) was employed to hardface structural steel using chromium carbide vanadium consumables, with results compared to AISI D2 cold-work tool steel. Four different SMAW parameters were tested, and the abrasive test was conducted against SiC discs. Wear rate, represented by the wear loss rate, was correlated to microstructure, scanning electron microscopy, energy-dispersive X-ray spectroscopy, hardness, microhardness, and surface roughness. The results showed that key SMAW parameters, such as welding speed and current, significantly influence wear resistance. Specifically, slower welding speeds and higher currents, which result in greater heat input, led to the increased wear resistance of the deposited layer through the mechanism of the inoculation of larger and harder carbides. © 2025 by the authors

The prospects for the development of Small Modular Reactors (SMRs)

The twenty-first century brings about a growing demand for higher energy production, coupled with the urgent need to protect the environment, which has already suffered significant damage. In response to this challenge, several countries, including the Republic of Serbia, are considering nuclear energy as a key component of their energy mix. Utilizing nuclear energy for electricity generation offers several advantages, including stable production and supply, low greenhouse gas emissions, and high safety standards. Several countries, including the Republic of Serbia, are considering turning to nuclear energy as a staple in the energy mix. The use of nuclear energy for the production of electricity is positive in terms of production and supply stability, low greenhouse gas emissions, as well as high safety. In contrast to the benefits of nuclear energy, there are significant drawbacks, such as the high cost of constructing and operating traditional nuclear power plants, the challenges associated with treating and disposing of radioactive waste, and the potential for large-scale accidents, which contribute to public fear. To address these issues, the development of small modular reactors (SMRs) has started. SMRs have lower costs compared to conventional reactors, and their potential for serial production can further reduce expenses by shortening both construction and licensing times. Additionally, because SMRs are more compact, they require reduced number of components necessary for transporting steam, such as pipes and pumps. Serial production enables the repetition of knowledge for operational work, especially since there will be multiple reactors of the same type. In addition to their economic development potential, Small Modular Reactors (SMRs) have significant opportunities for applications beyond electricity generation. For instance, they can be utilized in hydrogen production, which might be essential for various industries such as chemical manufacturing, metal processing, and as fuel for vehicles. There is also the potential to use Small Modular Reactors (SMRs) for applications such as process heating, district heating, thermal desalination, and reverse osmosis in the production of drinking water or for wastewater treatment. Although they are still in development, SMRs have the capacity to be widely adopted in the future, not only for power generation but also across various industries. This paper provides an overview of the benefits of SMRs as a promising new technology.International conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece

Advances in solid-state kinetics models: Case studies of pyrophyllite dehydroxylation and doped MgH2 dehydration

Pyrophyllite (Al2[Si4O10](OH)2) is material widely used in ceramics production, while MgH2 is often part of glass-ceramic electrolyte composites. The aim of this study is to investigated kinetics of pyrophyllite dehydroxylation and MgH2 dehydration, which are process important for above- mentioned applications. Pyrophyllite ore was mixed with 2 10 wt.% of AgNO3 and subjected to mechanochemical activation for varying milling durations. MgH2 was synthesized with the addition of 2 5 wt.% of W and Mo, also at different time intervals. All materials were characterized using X-ray diffraction, FTIR spectroscopy, dynamic light scattering, and scanning electron microscopy. For the pyrophyllite/AgNO3 composite, thermogravimetric analysis was performed, while for the doped MgH2, temperature-programmed desorption curves were used to investigate the reaction kinetics. Kinetic curves were modeled using several approaches. The classical kinetic model failed to describe either process accurately, suggesting that both exhibit dispersed kinetics. Mass loss during non-isothermal heating of pyrophyllite was described using a linear combination of two Weibull functions. In contrast, the dehydration of doped MgH2 required Brouers Sotolongo functions, which are more general representations of fractal kinetics. The kinetic parameters calculated from the modeled curves were correlated with the structural and morphological features of the materials.Advanced Ceramics and Application : 13th Serbian Ceramic Society Conference : Program and the Book of Abstracts; September 8-10, 2025; Belgrade

Topologically Protected Modes in Diamond-like Photonic Ribbons

The discovery of topologically protected modes has marked a major milestone in photonics, enabling robust light transport immune to disorder, backscattering, and fabrication imperfections. These modes have opened new possibilities in integrated photonic circuits, quantum information processing, and topological lasers. Recently, compact topological edge modes have been demonstrated experimentally in a quasi-one-dimensional ribbon structure with a hexagonal unit cell [1]. These modes combine the robustness of topological edge states with the spatial confinement of compact modes, offering dual-layer protection that makes them highly promising for applications. Here, we investigate the necessary conditions for the emergence of such modes in ribbon lattices composed of diamond-like unit cells. We design two different geometries in which an energy spectrum can be engineered through femtosecond (fs) laser writing of S- and P-type waveguides [2]. The specific ordering of couplings in the lattice induces an effective π-flux, which plays a key role in the band flattening mechanism. By continuously tuning this artificial flux, we theoretically demonstrate transitions between trivial and nontrivial topological phases. At Φ = π, all bands become flat, and compact localized states emerge. Using projector-based topological invariants and the mean chiral displacement method [3], we characterize the bulk-boundary correspondence and confirm the topological nature of the gapped bands and the associated edge modes.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia