Introduction: Cone beam CT (CBCT) is an excellent alternative in breast imaging since the breast is uncompressed while CBCT image quality is adequate, even in a dense breast. CBCT detector technology is based on CsI:Tl material, but recent research has explored photon counting detector technology adapted from nuclear medicine. A key question is whether an optimum detector configuration exists in terms of MTF (modulation transfer function), which reflects spatial resolution, and DQE (detective quantum efficiency), reflecting the overall image quality.

Methods: A micro-CBCT system was simulated in GATE (GEANT4 Application for Tomographic Emission) v.9.2, incorporating seven different detector configurations. The scintillators evaluated were BGO (light yield: 8000-10000 photons/MeV), LSO (25000-30000 photons/MeV), LYSO (30000-38000 photons/MeV), LaBr₃ (60000-70000 photons/MeV), GAGG (40000-60000 photons/MeV) and LuAG (18000-25000 photons/MeV) along with CZT as a semiconductor. These materials were selected due to their higher density and effective atomic number (Z_eff) compared to CsI, which can enhance DQE. Each scintillator (50x50x1 mm³) was discretized in 100x100 pixels and coupled to a generic SiPM (silicon photomultiplier) with a pixelated readout. A 40 keV X-ray spectrum was used. A 1 mm aluminum capillary and a cylindrical water phantom (20 mm height and 16 mm diameter) were simulated.

Results: GAGG demonstrated a 4% increase in spatial resolution and an 11% increase in DQE compared to CsI. Similar results were obtained from FBP (filtered backprojection algorithm) and OS-SIRT (ordered subset simultaneous iterative reconstruction technique)-reconstructed images. GAGG’s high light yield (40000-60000 photons/MeV), high density (6.6-6.7 g/cm³) and high Z_eff contribute to an improved signal-to-noise ratio (SNR). Additionally, it offers a fast decay time (80-100 ns) and low afterglow, good energy resolution, and robust mechanical properties.

Conclusions: GAGG is a strong candidate for CBCT detectors, offering improved spatial resolution, image quality and matching in SiPM readout systems.

A 2D material is a crystalline substance consisting of a single layer of atomic thickness. If any magnetically ordered material is exfoliated down to a single crystal lattice layer, its magnetic properties are likely to disappear at room temperature. This occurs due to thermal fluctuations, which readily destroy the magnetic order. The first magnetic 2D materials have recently been obtained, but most of them are unstable in air, hindering their practical application. These compounds exhibit novel magnetoelectric and magneto-optical properties, which are extremely important for spintronics. Layered chalcogenides of the FeGa2S₄ structure type represent a promising class of materials for the discovery of new two-dimensional systems.

The objective of the present work is to synthesize new layered magnetic compounds of the FeGa₂S4 structure type: FeAl₂S₄, FeAl₂Se₄, VGa₂S₄, and CrGa₂S₄, and to investigate their structure and magnetic properties. Bulk crystals of the target compounds can be used to obtain 2D materials via mechanical exfoliation, since the structural layers, bounded by sulfur or selenium atoms, are linked only by weak van der Waals interactions. This report will present the conditions for the synthesis of polycrystalline samples, as well as the growth of large bulk crystals using chemical vapor transport reactions. The crystal structure of the isostructural compounds has been studied by powder X-ray diffraction. The iron-containing compounds were also investigated by Mössbauer spectroscopy, and the selenide compound was examined by high-resolution transmission electron microscopy. The composition of the crystals was characterized by electron-probe microanalysis. The work presents measurements of the magnetic properties of the samples.

Introduction. Graph-theoretical concepts allow an alternative understanding of the role of symmetry in inorganic nanomaterials and offer a fine-grained look at the relative importance of their constituent atoms. Here, a link is shown between the concept of Equitable Partitions (EPs) of chemical graphs [1–3] and the distribution of local properties of nanoparticles.

Methods. The study focused on the geometrical and physical properties of idealised spherical and polyhedral nanoclusters of iron and cobalt. Clusters extracted from bulk lattices of the corresponding chemical elements were modeled as graphs based on nearest-neighbor adjacency, and their EPs were determined. The clusters were subjected to classical force-field modeling, as well as DFT calculations using the SIESTA software package [4].

Results. The following properties were determined: atom radial distances from the cluster center; a measure of forces on atoms; local charge densities; and local magnetic moments. Their values were found to be distributed according to the graph’s equitable partition; in other words, all atoms in a given partition cell share the exact same properties.

Conclusions. Our method sheds new light on the symmetries of inorganic nanomaterials and the role of individual atoms therein. Our findings can have implications in the understanding, design, and engineering of magnetic nanoparticles, catalyst materials, and other applications at the nanoscale.

References

1. I. Michos, V. Raptis. Graph Partitions in Chemistry. Entropy 2023, 25, 1504.

2. V. Raptis, A. Kaltzoglou. Graph Theoretical Analysis as an Aid in the Elucidation of Structure-Property Relations of Perovskite Materials. AIP Conf Proc 2024, 3030, 110005.

3. V. Raptis, I. Michos. Chemical Equitable Partitions: A new Perspective on Molecular Symmetries and Its Implications for the Study of Structure–Property Relationships. MDPI Proceedings 2025, 123, 6.

4. José M. Soler et al. The SIESTA method for ab initio order-N materials simulation. J. Phys.: Condens. Matter 2002, 14, 2745.

Spinel ferrite crystals are widely explored for magnetic hyperthermia, yet the design of crystal-chemistry “thermal brakes” that prevent overheating remains underdeveloped. Here we report a crystal structure-driven strategy to tune heating performance in hafnium-substituted magnetite nanocrystals, Hf_xFe_3-xO₄ ( x = 0.4, 0.6), synthesized by a scalable reverse co-precipitation route. X-ray diffraction confirms the cubic spinel structure across the series and reveals a systematic shift of the (311) reflection toward lower 2θ with increasing Hf content, consistent with lattice expansion and distortion induced by aliovalent substitution. The lattice parameter increases monotonically, while the coherent crystallite size decreases (≈10.6 → 7.9 nm), indicating enhanced microstructural disorder at higher substitution levels. Transmission electron microscopy shows quasi-spherical particles with comparable physical sizes (~12–14 nm), supporting a model where a reduced crystalline coherence length (rather than gross particle growth) governs structure–property changes. Magnetization measurements evidence a progressive decrease in saturation magnetization with Hf incorporation, consistent with modified cation distribution and increased surface/spin disorder. Under alternating magnetic field excitation, the specific absorption rate (SAR) decreases from pristine magnetite to Hf-doped (e.g., ~39.4 to ~8.1 W g^-1), yielding a controllable heating response that mitigates the risk of surpassing the therapeutic window. Baseline in vitro assays in MDA-MB-231 breast cancer cells (without AMF) support cytocompatibility within the tested concentration range, complementing prior ISO-guided viability results in non-tumor cells. Overall, these results establish lattice distortion and crystalline coherence as practical design knobs to engineer safer, dose-controlled hyperthermia agents based on spinel nanocrystals.

Transition metal borates have attracted considerable interest due to their rich crystal chemistry and diverse functional properties (magnetic, electrochemical, optical and others). These materials exhibit rare phenomena such as high magnetic ordering temperatures, cascades of magnetic transitions, and spin-liquid, glass and ice states. Owing to its unique combination of properties, FeBO₃ has been developed as a commercial Mössbauer source for synchrotron facilities [1]. In FeBO₃, the magnetic ordering temperature is high (T_N ≈ 348 K), whereas in Fe_1–xCr_xBO₃, it decreases with increasing Cr content [2].

In this work, FeBO₃ and CrBO₃ were investigated by in situ high-temperature powder X-ray diffraction (Rigaku Ultima IV, Cu Kα, 295–1173 K). Near T_N, FeBO₃ exhibits anomalous unit-cell behavior, whereas CrBO₃ shows no such anomalies. Both borates display positive uniaxial thermal expansion with low average coefficients: α = 8 (FeBO₃) and 6 × 10⁻⁶K⁻¹ (CrBO₃). The slight reduction in the expansion upon the Cr → Fe substitution arises from the smaller ionic radius of ^VICr³⁺ and shorter Cr–O bonds. FeBO₃ remains stable up to ~900 K, where a recrystallization to α-Fe₂O₃appears, while CrBO₃ is stable up to 1173 K. Thermal expansion is maximum along the c axis, i.e., perpendicularly to planes of the isolated BO₃ triangles, and minimum in the ab plane. These findings suggest that Fe_1–xCr_xBO₃ borates are promising candidates for synchrotron, optical and magnetic applications requiring tunable low thermal expansion.

The work is funded by the Russian Science Foundation [25-73-00080].

1. Potapkin, A.I. Chumakov, G.V Smirnov, J.-P. Celse, R. Rüffer, C. McCammon & L. Dubrovinsky, The ⁵⁷Fe Synchrotron Mössbauer Source at the ESRF, J. Synchrotron Radiation. 19 (2012) 559–569.
2. Muller, M.P. O'Horo, J.F. O'Neill, FeBO₃ solid solutions: Synthesis, crystal chemistry, and magnetic properties, J. Solid State Chemistry. 23 (1978) 115–128.

YF3:Er³⁺ nanoparticles (NPs) are characterized as possible intracellular nanoprobes for temperature measurements at the nanoscale. First, their spectral emission in the visible range is characterized and the excitation mechanism is studied through the observation of emitted intensity as a function of the excitation power. A slightly sub-linear excitation mechanism is observed. Then, their temperature-sensing ability in the typical biological temperature range is investigated by means of luminescence intensity ratio (LIR) measurements between two thermally coupled levels. We obtained a maximum relative sensitivity of 0.009 K^-1 at 24 °C with an uncertainty associated with the temperature measurements that ranges from 0.2 °C to 0.4 °C. The luminescence lifetime of the NPs embedded in various mounting media (air, agarose and ProLong) is measured from images acquired using a confocal time-gated microscope. Mean lifetimes observed are in agreement with the measured lifetime of this composition. Moreover, given the impact of the environment on the photophysical properties, we compared the measured lifetime of NPs embedded in different mounting media. The highest lifetime is measured when ProLong is used as a mounting medium, probably because of the hindered vibrational motion of water, which can act as a quencher molecule for NP luminescence. Luminescence lifetime in ProLong is ∼40% higher compared with the ones obtained in agarose and air, while lifetime in agarose is slightly higher than the one in air. NPs are then functionalized with poly (acrylic acid) (PAA) to improve both their water dispersibility and their uptake in cancer cells (HeLa). Cells are incubated with NPs and imaged by the time-gated confocal microscopy, which takes advantage of the long luminescence lifetimes of these NPs to temporally separate their emission from cellular autofluorescence. We demonstrated that PAA functionalization strongly improved cell internalization of the NPs and yielded smaller aggregates in solution with respect to non-functionalized NPs.

Seven new series of solid solutions (42 compositions total), doped with REE³⁺ ions, were synthesized based on two barium borate matrices: BaBi₂B₂O₇ and Ba₃REE₂(BO₃)₄ (REE = Y, Eu). Nine crystal structures were refined using single-crystal X-ray diffraction. Additional characterization included Raman spectroscopy, IR spectroscopy, thermal analysis , and high-temperature powder X-ray diffraction. Photoluminescence spectra were recorded for all series, and the temperature dependence of photoluminescence intensity was examined.

For the BaBi₂B₂O₇ matrix, solid solutions doped with REE³⁺ were obtained. The compositional ranges of continuous solid solutions were determined. Co-doping of the BaBi₂B₂O₇ lattice was found to expand the miscibility regions of the solid solutions. Eight crystal structures were refined from single-crystal data for BaBi_2−xEu_xB₂O₇ (Ñ… = 0.1, 0.2, 0.4), BaBi_2−xSm_xB₂O₇ (Ñ… = 0.05, 0.3), BaBi_2−xTb_xB₂O₇ (Ñ… = 0.1, 0.3, 0.4). All compounds crystallize in the BaBi₂B₂O₇structure type (hexagonal system, space group P6₃). The structure contains three independent crystallographic sites for large cations, each split into Ba and Bi subsites. REE³⁺ ions occupy the Bi subsites. Upon REE³⁺activation, the larger Sm and Eu ions preferentially occupy the M1 and M2 sites (largest coordination polyhedra volumes), whereas Tb³⁺, with the smallest ionic radius, occupies the M3 site (smallest polyhedral volume).

A new solid-solution series, Ba₃Y_2−xEr_x(BO₃)₄ (Ñ… = 0.01—0.3), along with end-member borates, Ba₃Y₂(BO₃)₄, Ba₃Eu₂(BO₃), was synthesized via melt crystallization. Thermal expansion was studied for Ba₃Eu₂(BO₃) and Ba₃Y₂(BO₃)₄, and the crystal structure of Ba₃Y₂(BO₃)₄ was refined across a wide temperature range (40 data points). Photoluminescence spectra and their temperature dependence were investigated for the Ba₃Y_2−xEr_x(BO₃)₄ series. The optimal activator concentration was determined to be x = 0.1.

This work was supported by the RSF (No. 22-13-00317-P) and utilized equipment from the "RDMI" and "OLMIV" of the Scientific Park of SPbSU.

Nowadays, in the rare events physics field, projects to study Neutrinoless Double Beta Decay (0νββ) are actively developing, as 0νββ-decay registration will allow calculating the energy and mass of neutrinos. 0νββ process is theoretically possible in a number of nuclei, one of most promising is ¹⁰⁰Mo [1], thus, the compounds with maximal ratio of molybdenum are of interest.

The use of light alkali metals as cations helps to reduce the scintillator's radiation background and increase molybdenum content in the compound. In turn, an increased molybdenum content in the crystal increases the probability of 0νββ-decay registration. In the course of this study, samples of the (Na,Li)₆Mo₉O₃₀ composition (x = 1-5 with a step of 1.0 were obtained by solid-phase synthesis. Solid-phase synthesis was carried out with a gradual increase in temperature until complete synthesis was determined in all samples. Completeness of the reaction, phase composition and unit cell parameters of the obtained samples were controlled using X-ray diffraction analysis.

Melting temperatures of the samples were determined by Differential Scanning Calorimetry (DSC). During the synthesis, it was found that the fractional composition sample had the lowest synthesis temperature (455 ÌŠC) of all the studied compositions, which confirms the hypothesis that the compound of this composition belongs to the eutectic point.

Based on the data obtained, stable phases in the binary system Na₆Mo₉O₃₀-Li₆Mo₉O₃₀ were identified. Conditions for growing single crystals using the low-thermal-gradient Czochralski technique were proposed.

. Acknowledgements

The study was supported by Russian Science Foundation grant No. 25-73-00328.

. Reference:

1. Agrawal A. et al. Development of MMC-based lithium molybdate cryogenic calorimeters for AMoRE-II// EPJ C. 2025. Vol. 85. â„– 172. P. 172-185

Disordered laser host materials have attracted significant attention due to their favorable spectroscopic properties, making them promising candidates for ultrafast laser gain medium applications [1,2]. In particular, disordered rare-earth orthovanadates provide an effective route for tailoring structural and optical properties through controlled cation substitution [2]. In this work, a 2.5 at% Yb³⁺-doped Y_0.7Gd_0.3VO₄ single crystal was grown along the [100] direction using the optical floating zone technique. Its structural, mechanical, and optical properties were systematically investigated and correlated. The selected composition introduces controlled Y/Gd substitutional disorder while preserving the structural stability of the zircon-type lattice.

Powder XRD confirm single-phase crystallization in the tetragonal structure (space group I4₁/amd) with refined lattice parameters a = b = 7.143 Å and c = 6.306 Å. High-resolution rocking-curve analysis of the (200) plane shows a narrow FWHM of 63.7 arc-sec, corresponding to a threading dislocation density of approximately 4.2 × 10⁶ cm^-2, indicating excellent crystalline perfection. Williamson–Hall analysis reveals microstrain of the order of 10^-4, attributed to ionic radius mismatch and substitution-induced lattice distortion. Vickers microhardness measurements demonstrate good mechanical robustness, with a hardness of about 4.8 Mohs, suitable for post-growth processing.

Polarized UV-Vis-NIR spectroscopy confirms strong optical anisotropy in the tetragonal zircon structure. The estimated optical bandgap is about 3.53 eV for π-polarization and 3.60 eV for σ-polarization. The absorption coefficient reaches ~16.47 cm^-1 under π-polarization compared to ~5.56 cm^-1 under σ polarization, with corresponding absorption cross-sections of ~5.47 × 10^-20 cm² (π) and ~1.82 × 10^-20 cm² (σ), confirming dominant π-oriented transitions. Photoluminescence spectra shows broad emission near 1020 nm under 985 nm excitation, corresponding to the ²F_5/2 → ²F_7/2 transition of Yb³⁺.

Overall, the Yb_0.025Y_0.7Gd_0.275VO₄ combines high crystalline quality with disorder-induced spectral broadening, highlighting the novelty of disorder-engineered orthovanadate hosts for broadband ultrafast solid-state laser gain media.

The effective value of the axial-vector coupling constant g_A​ in nuclear media represents one of the dominant sources of uncertainty in the interpretation of neutrinoless double-beta decay (0νββ) experiments. Its quenching relative to the free-nucleon value significantly impacts nuclear matrix element calculations and, consequently, the inferred values (limits) of the Majorana neutrino mass.

The GAIAS (GAxIal Analysis with Scintillators) project proposes a crystal-scintillator-based strategy to probe the g_A​ through high-precision measurements of forbidden non-unique beta decays. These transitions exhibit strong sensitivity of the beta spectral shape to the axial coupling constant, particularly in the low-energy region.

The method exploits key properties of scintillating crystals: a high light yield, low energy threshold (<5–20 keV), good energy resolution, high radiopurity, stable operation over a long time to accumulate a large enough statistic and the possibility of incorporating beta-emitting isotopes directly into the crystal bulk. Materials under investigation include CdWO₄, ¹⁰⁶CdWO₄​, CsI(Na,Rb), NaI(Tl,Tc), and CeCl₃​, hosting isotopes such as ¹¹³Cd, ^113mCd, ⁸⁷Rb, and ⁹⁹Tc either intrinsically or as controlled dopants.

The experiment is being installed in the low-background environment of the INFN Gran Sasso National Laboratory (LNGS), enabling high-statistics beta spectroscopy under stable and well-controlled conditions. Particular emphasis is placed on crystal growth strategies, isotope incorporation, control of scintillation non-proportionality below 100 keV, and long-term energy-scale stability.

By combining optimized crystal engineering, optimized electronic read-outs, precision spectroscopy, Monte Carlo simulations, and nuclear-structure modeling, GAIAS aims to extract g_A​ with high accuracy, strengthening the role of functional crystalline materials in fundamental physics.