I. Dumbryte, D. Narbutis, M. Androulidaki, et al.

Correlative characterization of micro-scale defects in heterogeneous mineralized materials requires the spatial fusion of measurement modalities that differ in resolution, contrast mechanism, and coordinate system. This study presents a non-destructive multimodal measurement methodology in which X-ray micro-computed tomography (µCT) and spatially selective photoluminescence (PL) spectroscopy are linked on an intact specimen by a 3D surface mesh-assisted spatial registration framework, with complementary energy-dispersive X-ray spectroscopy (EDS) used to characterize the associated compositional changes. The registration aligns the volumetric and point-resolved measurements with a spatial uncertainty bounded by the PL laser spot size (diameter 80 µm) and the µCT voxel size (7 × 7 × 7 µm3), both smaller than the spacing between adjacent measurement points, ensuring well-defined co-localization of crack-affected and pristine regions. The methodology was demonstrated on extracted human premolars with visible enamel microcracks: 192 polarization-resolved PL spectra per tooth, acquired at 325 nm excitation across 12 spatial positions (6 cracked, 6 pristine) and spatially registered to the µCT datacube, revealed a reproducible difference in spectral shape between crack-affected and pristine regions. A peak asymmetry index, defined as the ratio of the two emission maxima, was reduced in cracked regions consistently in both teeth and significantly when pooled across specimens (1.16 vs 1.28; p = 0.014), supported by EDS evidence of increased carbon content at crack sites (a 42% relative increase in averaged carbon content, with the carbon-to-oxygen ratio rising from 0.46 to 0.84). The validated measurement framework — its spatial registration with bounded uncertainty — is material-independent and generalizable to correlative volumetric and spectroscopic defect characterization in heterogeneous solids.

A. Torres-Huerta, M. de J. Velásquez-Hernández, S. Lempereur, L. Troian-Gautier, G. Veronesi, H. Valkenier

Precise stoichiometric control in multimetallic lanthanide nanosystems is essential for optical devices, sensing, and bioimaging applications owing to their composition-dependent emission properties. However, controlling metal composition, spatial distribution, intermetallic energy transfer, and colloidal stability remains challenging. Here, we report a liposome-based nanoreactor platform that enables the in situ formation of multivariate TbxEuy-dicarboxylate complexes, enabling finely tuned lanthanide stoichiometry within attoliter-scale confined volumes. Liposomes pre-loaded with specific Tb3+:Eu3+ ratios are combined with a synthetic anion transporter that mediates dicarboxylate transport through lipid membranes, enabling controlled coordination reactions in aqueous solution. This method, coupled with the use of a blue-emissive ligand, supports continuous color tuning across the entire RGB spectrum. Real-time emission spectroscopy reveals faster photoluminescence appearance for Eu3+ than Tb3+, providing experimental insight into lanthanide reactivity under nanoscale confinement. These findings position liposome-based nanoreactors as a versatile platform for investigating coordination reactions and engineering multimetallic luminescent colloidal materials in aqueous media.

J. Urbančič, F. Malchik, K. Zhumadil et al.

Ultrafast electron dynamics in a Ti3C2Tx MXene thin film (where Tx denotes surface terminations) were investigated using time-resolved photoemission spectroscopy with temporal resolution of 110 fs. Near-infrared optical excitation at 800 nm induces a transient redistribution of electronic states in the vicinity of the Fermi level, which is directly probed using extreme-ultraviolet (26.5 eV) pulses. The measured signal reveals a rapid modification of the electronic distribution immediately after excitation, followed by relaxation on sub-0.5 ps timescales, as quantified by the evolution of the electronic temperature. These results provide direct insight into hot-electron lifetimes and open the study of relaxation pathways in MXene thin films, establishing a framework for further understanding and optimizing their performance.