Publications

Composite x-at.% Yb:Y2O3/y-at.% Yb:Y2O3 (x = 0, 3, 5; y = 3, 5, 8) transparent ceramics with a graded doping profile of Yb3+ ions were obtained by solid-state reaction and multi-step sintering method. The multilayer ceramic compositions, consisting of two- and three-layers, were prepared by direct dry pressing of the constituent powders. Phase identification revealed that all sintered ceramics are well crystallized with a cubic structure similar to pure Y2O3, without impurity phases. Microstructural investigations have shown that the composite ceramics have a uniform morphology, with an average grain size of approximately 20 mu m, indicating that increasing the concentration of Yb3+ ions in the corresponding layers has no visible effect on the microstructure of the Y2O3 ceramics. Yb cations diffusion across the contact boundaries was investigated by the Energy Dispersive X-ray Spectroscopy analysis. Laser emission at 1.03 mu m was obtained from all ceramic samples, using quasi-continuous pumping at 971 nm with a fiber-coupled diode laser. This technique can be used to obtain multilayer ceramic structures, which could ensure for high-power lasers a controlled profile of the power absorbed in the active medium, or an efficient transfer of the heat generated during laser emission.

Overexpression of pyruvate kinase (PyK) is linked to many kinds of malignant tumors, representing therefore one of the most promising therapeutic targets for cancer treatment. Inhibition of PyK slows down tumor growth or causes tumor cell death, minimizing cancer cell proliferation, and understanding inhibitor mechanism of action can significantly improve cancer therapy. The present work describes the use of an amperometric bienzymatic biosensor, based on PyK and pyruvate oxidase (PyOx), in enzyme inhibition studies of four kinase inhibitors, CPG77675, Nilotinib, Ruxolitinib, Cerdulatinib. Their inhibition mechanism is studied and discussed in detail, with a thorough evaluation of their enzyme-inhibitor complex binding constants (Ki) and the inhibitor concentration required for 50% inhibition (IC50), employing standard inhibition procedure graphical methods. The biosensor is successfully applied for the quantification of the inhibitors by fixed potential amperometry, with excellent detection limit values in the pM range. It is the first detection method reported for the anticancer drugs CPG77675 and Cerdulatinib. The electrochemical assay based on the biosensor brings several advantages over the available assay kits for high-throughput screening (HTS) of kinase inhibitors, namely: low cost, easy operability and robustness demonstrated by biosensor high reproducibility and both operational and storage stability, offering an opportunity to discover new inhibitors and optimize their therapeutic index.

Sensing of volatile organic compounds (VOCs) not only in exhaled air but also in environmental air is essential in rapid diagnostication and in identifying potential hazards related to air quality, respectively. In particular, respiratory diseases like influenza and tuberculosis and other conditions like ketosis and diabetes can be investigated based on the detection of specific biomarkers in the exhaled products. At the same time, airborne pollutant contamination and air toxicity must be strictly and efficiently monitored. A practical and accurate VOC sensing device can be obtained using conductance changes induced in properly functionalized phosphorene active layers, which ensure specific binding sites for the targeted biomolecules. We develop here a multiscale approach that embeds an atomistic description based on density functional theory into a macroscopic transport model. In this way, we account for the electronic structure modifications induced in the active layer by the attached biomarkers with different configurations, which are extracted from ab initio molecular dynamics simulations. For the description of the device operation at the macroscopic level, we introduce a statistical model, which takes into consideration the proportion of the binding sites in the pristine active layer and the fractions of attached molecules. Perturbing factors like carbon dioxide, nitrogen, oxygen, and water molecules are investigated, and biomarker detection limits are evaluated. To improve the specificity of the biosensor, multiple sensing elements are employed, differently customized by transition metal impurities, which enhance the biomarker recognition capability. This allows the precise determination of the proportions of the molecules adhered to the device with the accuracy strictly dependent on the measurement resolution. Our results indicate that acetone and cyclohexanone detection is possible down to a few tens of ppm.

In this study, porous polysiloxane (PS)/multi-walled carbon nanotube (MWCNT) nanocomposite films were developed as high-performance triboelectric layers for flexible triboelectric nanogenerators (TENGs). TENGs convert mechanical motion into electricity and offer a promising solution for self-powered electronic systems. The nanocomposites were fabricated using a doctor blading method, and porosity was introduced via a simple, scalable salt-leaching technique. Sieved salt particles of varying sizes produced films with fine, medium, and large pores. Raman spectroscopy confirmed uniform MWCNT dispersion and strong interfacial interaction within the PS matrix. SEM analysis verified controlled pore morphology. Dielectric measurements showed reduced permittivity with increasing pore size due to air void incorporation. Triboelectric performance improved significantly with porosity; the medium porosity sample exhibited the best output with an open-circuit voltage of 65 V, short-circuit current of 6.9 mu A, and a power density of 280.6 mW m-2. This enhancement is attributed to the optimized combination of surface roughness, contact area, and dielectric behavior, promoting efficient charge generation and transfer. These results highlight the potential of microstructural engineering in porous nanocomposites for next-generation energy harvesting applications.

Herein, Cu(II)-doped SrSnO3 perovskites (SrSn1-x Cu x O3, namely SSO:Cux) were prepared by a modified Pechini method and applied as supercapacitors (SCs) for the first time. The effect of dopant concentration (x = 1, 2.5, and 5 mol %) was investigated to fine-tune the structural and electronic properties to design potential candidates as SCs. The SSO:Cux samples were characterized by conventional XRD and synchrotron XRD (S-XRD) combined with Rietveld refinements and spectroscopic analyses, such as Raman, FTIR, UV-vis, EPR, and XANES/NEXAFS. The electrochemical performance of the SSO:Cux samples was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic cycling with potential limitation (GCPL). It was evidenced that incorporating 2.5 mol % Cu(II) into the SrSnO3 perovskite lattice (SrSn0.975Cu0.025O3, SSO:Cu2.5) led to a significant change in structural disorder and electronic properties, which play an essential role in creating a mixture of point defects such as reduced Sn3+ and Cu+ cations, and oxygen vacancies (VO). The SC device constructed with the SSO:Cu2.5 material showed a specific capacitance of 613 F g-1 at a scan rate of 1 mV s-1, with a remarkable specific energy density and specific energy power of 25.42 W h kg-1 and 32678.57 W kg-1, respectively, which are higher than those observed for any other available perovskite-based SCs. This performance was primarily attributed to the formation of mixed Sn4+/Sn3+ and Cu2+/Cu+ cations, which alter the structural and electronic properties of SrSnO3. Our findings indicate that an improved capability to store high energy and power may be achieved by fine-tuning the Cu(II) dopant concentration in the lattice and controlling the formation of undesired phases. This offers experimental guidance to design other Cu-doped perovskites as alternative materials for energy storage applications.

This study covers three complementary aspects; it focuses first on analyzing the turn-on and turn-off processes of the power CoolMOS transistor and investigating its switching times. Furthermore, it expands the scope of our previous works by validating the dynamic behaviour of the proposed model of the power CoolMOS transistor and it assesses the influence of the external gate resistance on the device's switching performance. Simulation results for the switching characteristics were verified through experimental measurements. An experimental test was carried out using a resistive load circuit with different external gate resistance values to analyze its impact on the device's switching behavior. The findings confirm the accuracy of the conclusions drawn from the theoretical and simulation analyses presented in this paper.

We report the synthesis and characterization of folic acid (FA)-conjugated human serum albumin nanoparticles, (HSA-FA):Ru NPs, as targeted carriers for rutin (Ru), a flavonoid with known anticancer activity. Nanoparticles were fabricated via a desolvation method, and their surface was functionalized with folic acid to promote selective uptake by cancer cells overexpressing folate receptors. Morphological and dimensional analyses performed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and fluorescence microscopy confirmed that all nanoparticles were below 100 nm and exhibited good colloidal stability. Voltametric measurements confirmed the successful incorporation of both rutin and folic acid within the (HSA-FA):Ru nanoparticle formulation. Biological evaluation was conducted on healthy L929 fibroblasts and HT-29 colon adenocarcinoma cells. MTS colorimetric assays revealed that (HSA-FA):Ru NPs significantly reduced the viability of HT-29 cells, while maintaining higher compatibility with L929 cells. Fluorescence and electron microscopy further confirmed preferential nanoparticle uptake and surface accumulation in HT-29 cells, supporting the role of folic acid in enhancing targeted delivery. The study demonstrates that HSA-based nanoparticles functionalized with FA and loaded with Ru offer a biocompatible and efficient strategy for selective intracellular drug delivery in colorectal cancer. These findings support the use of albumin-based nanocarriers in the development of targeted therapeutic platforms for cancer treatment.

The crystallization mechanism of Yb/Er-doped GdF3 nanocrystals in silica nano-glass ceramics was analyzed using model-free and model-fitting methods and thermal analysis data in correlation with structural data. The formation of GdF3 nanocrystals occurs at around 300 degrees C, and their size is temperature dependent, ranging from 14 to 40 nm, depending on the processing temperature. A similar trend is observed for cell volume, where a contraction of up to approximate to 2.3% (at 600 degrees C) was assigned to the gradual incorporation of Li and Yb,Er dopants. Model-free analysis showed an increase in activation energy (Ea) and the preexponential factor (log A) up to 175 kJ mol-1 and 14.8 s-1, respectively, until the completion of crystallization. Model-fitting analysis indicated a crystallization process controlled by an autocatalytic-type reaction where a second metastable phase (LiF) acts as a catalyst and facilitates a rapid and self-accelerated crystallization of the main GdF3 nanocrystalline phase. The ceramization process boosted UC luminescence up to values comparable to those of NaYF4:18Yb/2Er.

Due to the importance of buffer layers in interface engineering, the development of more variants and the rational design of materials have a significant influence on the performance of optoelectronic devices. This study provides a strategy to increase device performance by facilitating efficient charge transfer and defect passivation by combining the properties of eco-friendly materials (adenine, cytosine, guanine, thymine, and uracil) with the physicochemical properties of metal oxides. The aim of this paper was to investigate the interaction of zinc oxide (ZnO) nanostructures (seed, nanoparticles, and nanowires) with nucleobase layers and to discuss their potential applications as organic-inorganic interfacial bilayers. The impact is analyzed from structural, morphological, optical, and electrical points of view. Nucleobase-ZnO nanostructure layers present high optical transparency in the visible range. Electrical measurements confirmed that the high surface area of nanowires can enhance interactions with nucleobases, leading to better charge transfer. The results showed that these nucleobase-ZnO nanostructure layers are promising interface materials for enhancing optoelectronic device performance through interfacial charge transport and light management, while enabling the design of environmentally friendly devices.

Paper-based devices hold great promise in biosensing, but the choice of electrode materials influences performance. Here, we report a paper-based electrochemical sensor developed for nucleic acid quantification, in a sandwich-type architecture integrating 3-electrode systems on metallized electrospun polymeric fibers. A 3D-printed hydrophobic barrier on the chromatographic paper defines injection and testing zones. Fluid diffusion through paper and concentration gradients are considered in the design. Electrochemical characterization is performed using 40 mu L of methylene blue solution, which interacts with double-stranded nucleic acids, reducing its redox activity. This interaction mechanism within the paper substrate is confirmed by spectroscopy. The sensor achieves detection of nucleic acids in 3 min with 2 mu L of solution. Real sample analysis is performed for the quantification of PCR-amplified genes with a limit of detection of 1.38 ng mu L-1. The device serves as a promising point-of-care diagnostics tool for the direct quantification of amplified genetic material.