Publications

In 2025, the Year of Quantum Science and Technology (https://quantum2025.org/), we celebrate a century of quantum mechanics, witnessing a surge in activities that illuminate its inherent strangeness and drive technological innovation. Superconductivity, discovered 114 years ago, stands as a prime example, offering direct and compelling evidence of macroscopic quantum phenomena. Beyond its ability to conduct immense currents without loss, superconductivity reveals the quantum realm operating on a scale we can directly observe and manipulate. The macroscopic quantum coherence, where an ensemble of particles is described by a single wave function, leads to remarkable consequences: dissipation-less current and flux quantization-the basic properties exploited in superconducting quantum circuit fabrication. This Roadmap has been inspired by intensive discussions and collaborations emerging from the European Cooperation in Science & Technology COST-Action CA21144 (SuperQuMap-Superconducting Nanodevices and Quantum Materials for Coherent Manipulation). The aim of the COST Action SuperQuMap is to establish a strong European network centered on macroscopic quantum behavior in superconductors, bringing together groups of different backgrounds and more than 30 countries. The roadmap outlines the network's concrete activities, driving advancements in superconductor-based quantum technologies and charting future directions. Spanning fundamental research to practical applications, the roadmap incorporates insights from industry partners developing quantum computation. It begins by exploring quantum materials, highlighting how topology and electronic correlations could catalyze a quantum leap in technology. We then delve into manipulating the superconducting phase, leveraging advancements in magnetism, 3D fabrication, and tunable correlations. Further, we showcase the advanced microscopy techniques-such as angle-resolved photoemission spectroscopy and scanning probes-used to visualize quantum behavior. Finally, and crucially, we detail the quantum devices developed within the network, and their transformative impact on modern quantum computing approaches.

A set of yttrium-gadolinium ferrite powder and ceramic samples (Y3-xGdxFe5O12, x = 0.0-1.0) was comprehensively investigated to elucidate the mechanisms that govern the formation of garnet structure. The objects of investigation were synthesised by means of precipitation in aqueous solutions followed by annealing and sintering (for ceramic samples) at temperatures up to 1400 degrees C. The employment of X-ray diffraction and Fourier-infrared spectroscopy has enabled to reveal the key features associated with the crystal structure formation in dependence on the concentration of gadolinium. The formation of a garnet structure is demonstrated to occur in two stages, where the initial stage includes the formation of an intermediate orthorhombic perovskite phase. The substitution of yttrium cations with gadolinium ones is shown to exert a non-monotonous effect on these processes. A significant finding of this study is that the presence of Gd dopant results in a substantial decrease in the temperature of the garnet structure formation. This decrease is approximately 100 degrees C within the concentration range that was studied, and for specific concentrations (x = 0.4 and x = 1.0), it reaches 200 degrees C that is technologically relevant for energy-efficient materials processing. In ceramic samples derived from the synthesised particles, the increase in gadolinium concentration is found to result in a decrease in porosity and a non-monotonous transformation of static (saturation magnetization, coercivity) and dynamic (ferromagnetic resonance linewidth) magnetic parameters. This study delineates the critical insights into the development of yttrium-iron garnets-based materials, offering the practical approaches for improving their structural and physical parameters to enhance utilization for microwave applications.

Since 2016, a peculiar trend in the synthesis of layered double hydroxide solids involves the use of organic alkalis, e.g., quaternary ammonium hydroxides that play the role of a synthesis agent as well as a template molecule. This approach adapts the tailored textural properties of the final solid, also eliminating the occurrence of disadvantages due to the use of inorganic alkalis in the synthesis process of LDH-type solids (e.g. possibility of contamination with alkali metals, high energy consumption, significant waste production, etc.). However, the attempt to insert the copper cation into the octahedral positions of LDH using the organic alkali (i.e. tetramethylammonium hydroxide) leads to the obtaining of a layered structure contaminated with Cu(OH)2. The nature of the precursor used for LDH synthesis plays a particular role because, for example, the use of sulfates leads to ill crystallized structures due to their lower reactivity. Regardless of the synthesis method used (co-precipitation as a traditional method or mechanochemical as a non-traditional one) and the nature of the precursors involved (nitrates, chlorides, sulfates) in the synthesis process, copper was not completely inserted into the octahedral positions for the molar ratio of divalent cations considered, i.e. Cu/Mg=1. The use of tetramethylammonium hydroxide as a synthesis agent also generates tailored textures where the surface areas were in the range of 0.9 and 19.5 m2 & sdot;g-1. The electronegativity values of the cations involved, e.g. Mg, Cu and Al, played an essential role in determining the basicity values. Both the basicity and the catalytic activities kept a linear variation trend in the Claisen-Schmidt condensation between benzaldehyde and cyclohexanone. The low basicity and the presence of acid sites due in particular to the presence of the Cu cation in the solid structure, a fact perceived as a disadvantage in base-catalyzed reactions, actually represented the key to the selectivity of the transformation into the mono-condensed product (2-benzylidenecyclohexanone). In accordance with this trend, the amount of the thermodynamically favored product, i.e. 2,6-dibenzylidenecyclohexanone (di-condensed product), decreases. The highest cyclohexanone conversion of 88.4 % was presented by D-NO3--MC (with 97.3 % as selectivity to di-condensed product). A similar result was obtained for Hy-NO3--CP. Meanwhile, C-SO42--CP generated 46.3 % conversion of benzaldehyde to benzoic acid in a side reaction. The catalysts obtained from nitrate precursors, allowed reaching higher conversions of cyclohexanone with enhanced selectivity for the di-condensed product. After 3 reaction cycles, especially Al and Cu were extracted from the octahedral positions leading to the formation of side phases, e.g. hydroxides, carbonates, hydroxycarbonates, but also dypingite like phase.

Y-branched TiO2 nanotubes (NTs) were produced by anodizing titanium plates derived from aerospace production leftovers and subsequently engineered to develop an enhanced TiO2-based photocatalytic system. The NTs were electrochemically reduced to obtain reduced TiO2 nanotubes (rTN) with a narrowed bandgap, followed by surface modification with polydopamine (PD) and silk fibroin-derived quantum dots (QDs) to promote enhanced UV and visible-light photocatalysis for wastewater treatment. The QDs were hydrothermally synthesized from Bombyx mori silk fibroin. Scanning Electron Microscopy (SEM) revealed spherical QD agglomerates encapsulated within the PD layer, while Energy Dispersive X-ray Spectroscopy (EDX) confirmed the presence of carbon and nitrogen originating from both PD and QD. The resulting rNT/PD/QD photocatalyst exhibited a significantly reduced bandgap (1.03 eV), increased Urbach energy (1.35 eV), and moderate hydrophilicity. A high double-layer capacitance (C-dl) indicated an enlarged electrochemically active surface due to the combination of treatments. Electrochemical characterization demonstrated reduced electrical resistance, higher charge density, and lower electron-hole recombination, leading to improved interfacial charge transfer efficiency and electrochemical stability during multi-cycle cyclic voltammetry measurements. Preliminary photocatalytic tests show that the rNT/PD/QD photocatalyst achieved a degradation efficiency of 79.26% for methyl orange (MO) and 35% for tetracycline (TC).

The paper presents a comparative experimental study of heat-transfer behavior in three alloys considered candidate materials for nuclear reactors: the austenitic stainless steel 316L, Zircaloy-4 (currently used in CANDU reactors), and an ODS alloy with a ferritic matrix. The investigation was conducted across five temperature intervals, each sample being subjected to a thermal shock through short-term overheating to the upper limit of its respective interval. The variation of thermal diffusivity in the three alloys was determined as a function of both measurement temperature and applied thermal shock, and trends in heat-transfer behavior were compared across the five temperature ranges. The experimental results show that up to 400 degrees C, Zircaloy-4 exhibits the highest thermal diffusivity, followed by the ODS alloy, with the lowest values measured for 316L steel. At approximately 450 degrees C, the ratio between 316L and the ODS alloy reverses. Beyond this point, increasing the temperature up to 900 degrees C is accompanied by a continuous rise in thermal diffusivity for both 316L stainless steel and Zircaloy-4. In contrast, for the ODS steel, increasing temperature leads to a continuous decrease in thermal diffusivity, reaching a minimum near the Curie point. The novelty of the study lies in the comparative assessment of the influence of temperature on the heat-transfer process in three alloys relevant to nuclear energy, covering the operating temperature ranges of CANDU and ALFRED reactors, as well as potential accidental overheating up to 900 degrees C. A particular feature of the work is the prior application of a short-duration overheating step produced using solar energy. The results are relevant not only for nuclear reactors but also for other high-temperature applications in corrosive environments.

Graphene oxide (GO) nanosheets (0.5-2.0 phr) were incorporated into nitrile-butadiene rubber (NBR) to clarify how interfacial chemistry and dispersion control macroscopic performance. GO was synthesized by a modified Hummers method, and different filler concentrations of NBR/GO were prepared via solution-coagulation followed by sulfur vulcanization. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirmed multilayer GO and best sheet dispersion at 1 phr, whereas 2 phr showed initial aggregation. Fourier-transform infrared spectroscopy (FTIR) confirmed that the NBR backbone and nitrile groups remained intact, while weak GO-derived C-O-C/C-O bands appeared at higher loadings. The C equivalent to N band at similar to 2,237 cm-1 preserved its position but showed a slight increase in bandwidth, consistent with the formation of a hydrogen-bonded interphase. X-ray diffraction (XRD) showed loss of GO periodicity in the rubber matrix. UV-Vis/Tauc analysis indicated a non-monotonic band gap (direct 3.01 -> 3.13 -> 3.11 eV; indirect 2.84 -> 2.92 -> 2.96 eV), arising from confinement at well-dispersed loadings and pi-pi stacking at higher loadings. Dielectric measurements (102-106 Hz, 20 degrees C-100 degrees C) evidenced a more stable epsilon ' for GO-filled samples, maximized at 1 phr. Mechanical testing showed simultaneous gains in tensile strength, tear resistance, and rebound elasticity at low GO loadings, while swelling and thermo-oxidative retention improved due to barrier effects and chain immobilization. Overall, similar to 1 phr GO delivers the best structure-property balance, combining hydrogen-bond-mediated interfacial adhesion and optimal dispersion with stable dielectric behavior and reduced swelling/aging sensitivity; 2 phr yields the highest tensile value but also results in incipient aggregation and reduced dielectric stability.

We approach a cost effective, environmentally friendly, synthesis route of a non-precious electrocatalysts for the anodic oxidation of bioethanol. SnO2 and SnO2-Graphene Nanoplatelets are decorated with nano-crystallized Ni filaments and clusters with peculiar surface chemistry. The electrocatalysts are obtained by subsequently depositing different Ni species by wet impregnation in the presence or absence of a reducing agent (Na borohydride). The effect of the Ni deposition parameters on the crystalline and porous structures, on the surface chemistry and on the electrochemical behavior is highlighted. It is found that the use of a lower temperature (200 degrees C) thermal treatment in the presence of a reducing agent leads to an increase of more than five times of the specific surface area. Electrocatalytic performance is assessed in alkaline medium and, apparently, graphene addition to the SnO2-nickel support allows diminishing the Tafel slope with ca. 20 %, down to 106 mV decade(-1). Such value, that favorably compares to those in the literature, together with the good resistance to fouling that the results of the chronoamperometric and electrochemical impedance spectroscopy (EIS) measurements demonstrate, show that the composites are worthy of development as active materials for biofuel cell applications.

ZnO is recognized as one of the most versatile semiconductor materials, due to its adjustable properties, making it ideal for various applications. Herein, C-doped ZnO nanoparticles were obtained by thermal decomposition and tested as photocatalysts for water depollution and electrode materials in a symmetric supercapacitor device. These nanoparticles exhibited polyhedral shapes with sizes ranging from 95 to 104 nm. The impact of the doping level on the evolution of defect centers was analyzed using EPR and PL spectroscopy. Under visible light, the photocatalytic performance was tested against two contaminants, Rhodamine B (RhB) dye and oxytetracycline (OTC) antibiotic. A 1% C doping level provided the optimal photocatalytic performance, achieving degradation rates of 80% for RhB and 50% for OTC. The photodegradation process was elucidated by examining ROS species generated, linked to the measured valence band position and defect levels. Additionally, the same sample showed superior electrochemical performance when tested in a symmetric supercapacitor device, achieving a maximum specific capacitance of 104.16 F/g at a 2 mV/s scan rate, with an energy density of 14.46 Wh/kg and excellent cyclic stability, retaining 99% capacity after 2000 cycles. These findings highlight the versatility of C-doped ZnO nanoparticles, making them effective in environmental remediation and energy storage applications.

This study explores synthesizing and characterizing LaPO4:Sb3+/xMn2+ (LSBMx) phosphors (x = 0%-5%) prepared via the co-precipitation method. Structural analysis and luminescence properties reveal that LSBM0 (without Mn2+) emits blue light under UV excitation, while Mn2+-doped samples exhibit tunable emission from blue to orange-red. Under UV excitation, LSBMx phosphors demonstrate a broad visible emission band with multiple peaks attributed to the 4T1(4G) -> 6A1(6S) transition of Mn2+. The broad emission band (520-660 nm) can be deconvoluted into four Gaussian components centered at 564 nm (Mn-I), 595 nm and 616 nm (Mn-II), and 648 nm (Mn-III), corresponding to Mn2+ in La3+sites due to charge inconsistency, crystal field modifications induced by Sb3+ incorporation, and Mn2+- Mn2+ dimers, respectively. Energy transfer efficiency calculations determine the optimal Mn2+ concentration to be approximately 3%. This novel phosphor system demonstrates versatile green, orange, and red emission capabilities, establishing a valuable framework for developing Mn2+-doped luminescent materials with potential applications in LED lighting technology.

Boron-doped silicon detectors used in high radiation environments like the future HL-LHC show a degradation in device performance due to the radiation induced deactivation of the active boron dopant. This effect, known as the so-called Acceptor Removal Effect (ARE), depends on particle type, particle energy and radiation dose and is usually explained by the formation of boron-interstitial-oxygen-interstitial (BiOi) defects that induce a donor-type defect level in the upper part of the Si band gap. Here we present defect characterization studies using Thermally Stimulated Current technique (TSC) and Deep Level Transient Spectroscopy (DLTS) on a set of epitaxially grown p-type silicon diodes of different resistivity, irradiated with 60Co gamma-rays. We used the defect parameters (activation energy, charge carrier capture cross sections and defect concentration) obtained from DLTS experiments for modeling the corresponding TSC spectra, and subsequently compared those with the experimental TSC results. This approach shows that the di-vacancy which is well characterized by DLTS correlates with the so-far unspecified charge emission signal of the X-defect that partially overlaps with the BiOi peak in TSC spectra. Additionally, in order to evaluate the impact of BiOi defect formation on the macroscopic properties of the device, we compared the BiOi defect concentration with the change in the effective carrier concentration Neff obtained from C-V measurements. It shows that the variations in Neff are about twice the changes in the BiOi concentration, which corroborate the assumption of boron deactivation by the formation of the BiOi donor in irradiated p-type Si.