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

Mechanical and biodegradability properties of synthesized bio-membranes from waste hemp fibers

In this study, waste hemp fibers were transformed into cationically modified materials through a two-step process. The process began with the collection of agricultural waste fibers after hemp harvesting, followed by a delignification pretreatment, and subsequently, quaternization using the synthesized Deep Eutectic Solvent of chlorocholine chloride and urea. To form the material into membranes, both unmodified and modified fibers were cross-linked under pressure using citric acid as a natural cross-linker. The structural and chemical characteristics of the formed membranes were analyzed using SEM and FTIR techniques. The mechanical properties of the membranes were determined by measuring the breaking force and calculating the tensile strength via the Brazilian test method. Biodegradability was assessed by examining the mass loss of membranes composed of unmodified and cationized hemp fibers over 90 days, using a Soil Burial Test (AATCC Test Method 30-1993) in controlled laboratory conditions (24 °C). The results demonstrated a significant improvement in the tensile strength of the synthesized material (2.41 MPa), attributed to the synergistic effect of physical intermolecular interactions within the cationically modified hemp membranes (WCHM) and enhanced cross-linking using citric acid. The newly synthesized membrane showed great potential as a biodegradable material, with the first signs of degradation, reflected by a 25% mass loss, observed after 14 days. A slightly faster degradation rate was noted for unmodified fibers, highlighting the effectiveness of citric acid as a cross-linker.MME SEE 2025 : 6th Metallurgical & Materials Engineering Congress of South-East Europe; 4-7 June 2025; Trebinje, Bosnia and Herzegovina

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

Sustainable gamma irradiation strategy for GO and rGO modification: Impact on electromagnetic interference shielding efficiency

Electromagnetic interference (EMI) has emerged as a significant issue in contemporary electronic systems, particularly within aerospace, defense, and communication technology. Graphene-derived materials, including graphene oxide (GO) and reduced graphene oxide (rGO), present remarkable potential for lightweight, flexible, and EMI shielding solutions owing to their adjustable electrical conductivity and structural integrity. This study introduces an eco-friendly method for adjusting the EMI shielding effectiveness (EMI SE) of free-standing films made from GO and rGO by controlled gamma irradiation at low (50 kGy) and high (300 kGy) doses, conducted in two types of media: air and isopropyl alcohol (IPA). The structural alterations generated by irradiation were characterized by Raman and Infrared spectroscopies, X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements, indicating changes in defect density, surface roughness, and hydrophilicity. Results indicate that gamma irradiation can precisely adjust the oxidation/reduction equilibrium, hence boosting conductivity in rGO and improving interfacial polarization in GO. Remarkably, rGO films exposed to air demonstrated exceptional EMI SE values above 20 dB in the X-band (8–12 GHz), signifying their suitability for advanced shielding applications. This research illustrates the effectiveness of gamma irradiation as an environmentally friendly, scalable method for modifying the characteristics of graphene-based materials, facilitating their incorporation into advanced aeronautical and electronic equipment

COMSOL Modelling of Chromium(VI) Adsorption on Citric Acid Functionalized Chitosan Hydrogel Beads

The COMSOL Multiphysics is a software tool with a graphical user interface (GUI) for modeling and solving partial differential equations using the Finite element method (FEM) together with adaptive meshing and error control using a variety of numerical solvers. To predict the breakthrough curves for Cr(VI) adsorption in a continuous fixed-bed column packed with citric acid functionalized chitosan hydrogel beads (CA-GLA-CHB) as adsorbent, the axially dispersed plug flow model described by the Advection-Dispersion-Reaction (ADR) equation was implemented and solved numerically by COMSOL Multiphysics software. The validity of the proposed mathematical model under different operating conditions was evaluated by comparing the experimental breakthrough profiles with those simulated by the software. Using the software, the column geometry, material properties characterized by diffusion, porosity, adsorption capacity and flow rate were defined. The equilibrium adsorption data obtained by batch experiments described by Langmuir isotherm were incorporated in calculations. Based on the experimental values, it was obtained that the value of the axial dispersion coefficient, Dz, has a significant impact on the shape of simulated Cr(VI) breakthrough profiles. The breakthrough curves based on the Rastegar-Gu correlation and the fitted Dz values showed higher R2 values, in the range of 0.961 – 0.993 and 0.975 – 0.994, respectively, and the predicted breakthrough time and exhaustion time were much closer to the experimental values compared to the breakthrough curves based on the Dz value calculated from the Chung-Wen correlation. Therefore, the proposed mathematical model based on either Rastegar-Gu correlation or the fitted values of Dz can be used to accurately predict the concentration profiles of Cr(VI) ions at the outlet of a fixed-bed column using COMSOL Multiphysics software. The ultimate goal of this work is to confirm the correctness of the COMSOL calculations for future application in large-scale fixed column wastewater treatment systems.Materials, Methods & Technologies : 27th International Conference; 14-17 August 2025; Burgas, Bulgaria

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

Defect Engineering and Opening of the Ion tracks in the Swift Heavy Ion Irradiated Thin Films of Bismuth Vanadate: Impact on Oxygen Evolution Reaction for Solar Water Splitting

Swift heavy ion (SHI) irradiation (Xe ions, 150 MeV, 5 × 109 – 5 × 1011 ions cm-2) is utilized to engineer defect landscape in hydrothermally synthesized BiVO4 (BVO) thin films, aiming to understand its role in photoelectrochemical (PEC) performance toward oxygen evolution reaction (OER). Our findings show that SHI irradiation, from individual to overlapping ion tracks, induces residual stress and amorphization in BVO, accompanied by the formation of bismuth-rich hillocks above oxygen-depleted ion tracks. While high fluence irradiation results in the irreversible reduction of PEC activity, the lower fluences (5 × 109 ions cm-2 and 1 × 1010 ions cm-2), induce defects that initially trap charge carriers, but over time lead to 58.6 % and 25.2 % increase in the photocurrent density, respectively. Detailed post-PEC morphological analysis reveals opening of ions tracks and the formation of nanoscale holes, reaching up to 30 nm in diameter and up to 200 nm in depth. Our study establishes a link between defect creation and PEC performance in BVO thin films, paving the way for innovative approaches to its morpho-structural manipulation and nano-structuring while simultaneously contributing to the fundamental understanding of SHI-induced phenomena in BVO films.This is the peer-reviewed version of the paper: Jelić, M., Jovanovic, Z., Kornieieva, K., Daneu, N., Gupta, S., O’Connell, J., Vershinina, T., Kirilkin, N., Orelovitch, O. L., Stojković Simatović, I., Skuratov, V., & Jovanović, S. (2025). Defect Engineering and Opening of the Ion tracks in the Swift Heavy Ion Irradiated Thin Films of Bismuth Vanadate: Impact on Oxygen Evolution Reaction for Solar Water Splitting. J. Mater. Chem. A. [https://doi.org/10.1039/D4TA09066G

Synthesis and characterization of Cu(II)‑meso-HMPAO complex as a model for the development of potential 64Cu radiopharmaceutical

In this work, Cu(II) complexes with meso‑HMPAO and d,l-HMPAO were synthesized. The structural characterisation of the isolated compounds has been done by single-crystal X-ray diffraction analysis, FTIR, and mass spectroscopy. Redox properties of complexes and binding to deoxyribonucleic acid (DNA) molecule have been analysed in detail by cyclic voltammetry and DFT calculations. The results of cyclic voltammetry fully agree with the data obtained by DFT calculations and indicate that the first electron removal takes place from the metal, while the second electron is removed from the ligand. The formation of the complex leads to the shift in oxidation peaks of the ligand from ‒0.29 V to 0,47 V and from 1.18 V to 1,24 V, indicating that ligand in the complex is much more difficult to oxidize. Electrochemical data confirmed the binding between the complex and DNA molecules through guanine. DFT calculations show that the complex is suitable not only for binding purine and pyrimidine bases through a coordination bond but also for additional hydrogen and CH-π interactions of the bases with the ligand. The fluorescence titration experiments revealed a moderate binding affinity of the [Cu-HMPAO]ClO4 complex to human serum albumin (HSA). Molecular docking revealed that this ligand preferentially binds to drug binding site 3 of HSA. Therefore, the novel compounds could be of great interest for further investigation, considering the potential anticancer activity, and as a model for the development of radiopharmaceutical with 64Cu.This is the peer-reviewed version of the article: Mirković, M., Belaj, F., Perić, M., Stanković, D., Radović, M., Milanović, Z., ... & Mihajlović-Lalić, L. E. (2025). Synthesis and characterization of Cu (II)‑meso-HMPAO complex as a model for the development of potential 64Cu radiopharmaceutical. Journal of Molecular Structure, 1321, 139791. [http://dx.doi.org/10.1016/j.molstruc.2024.139791