Publications

The outstanding properties exhibited by the p-type NiO nanostructures can be greatly affected by morpho-structural and defect characteristics with constructive or competing effects. We have conducted an in-depth study on NiO nanoparticles obtained by hydrothermal synthesis and submitted to various thermal treatments, to monitor the evolution of their structural properties and the effect of the thermal history on their CO sensing. Correlated electron paramagnetic resonance and analytical transmission electron microscopy investigations evidenced an amount of up to 1 % metallic nickel clusters close to surface in the NiO nanoparticles calcined at 400 degrees C and 500 degrees C for 8 h. Subsequent annealing in vacuum and in air of the sample calcined at 400 degrees C resulted in different size distributions and morphology of the NiO nanoparticles and an increase/decrease of the nickel phase, respectively. Comparative CO sensing tests on the two pristine samples and on the sample calcined at 400 degrees C and further annealed in air at 500 degrees C for 2 h showed an increase in the baseline resistance of the later due to the decrease of free charge carriers induced by the dissolution of the nickel clusters. The overall CO sensing results show a strong dependence on the samples thermal history.

Quantum electrodynamical density functional theory is applied to obtain the electronic density, spin polarization, as well as orbital and spin magnetizations of square periodic arrays of quantum dots or antidots subjected to the influence of a far-infrared cavity photon field. A gradient-based exchange-correlation functional adapted to a 2D electron gas in a transverse homogeneous magnetic field is used in the theoretical framework and calculations. The obtained results predict a non-trivial effect of the cavity field on the electron distribution in the unit cell of the superlattice, as well as on the orbital and spin magnetizations. The number of electrons per unit cell of the superlattice is shown to play a crucial role in the modification of the magnetization via the electron-photon coupling. The calculations show that cavity photons strengthen the diamagnetic effect in the quantum dot structure, while they weaken the paramagnetic effect in the antidot structure. As the number of electrons per unit cell of the lattice increases, the electron-photon interaction reduces the exchange forces that will otherwise promote strong spin splitting for both the dot and the antidot arrays. Electronic density, spin polarization, as well as orbital and spin magnetizations of square periodic arrays of quantum dots or antidots subjected to the influence of a far-infrared cavity photon field are obtained using quantum electrodynamical density functional theory adapted to a 2D electron gas in a transverse homogeneous magnetic field. image

This paper tackles the influence of the functionalization of polystyrene and graphene oxide (GO) composites on the flammability characteristics. A microscale combustion calorimeter (MCC) was used to experimentally determine the heat release capacity (HRC), the specific heat release rate (HRR) and the total heat released (THR). Neural models were designed that correlate the THR with a number of parameters related to the composition and type of flame retardant used, the heating rate, the amount of residue, the HRC, the peak heat release rate (PHRR), the temperature at the peak pyrolysis rate (TPHRR) and the time elapsed until the occurrence of the peak heat release rate (Time). The best results in the training, validation and testing stages were achieved with the neural model with 9 neurons in the input layer, 40 neurons in the hidden layer and one neuron in the output layer. This model was incorporated into an optimization procedure, based on a genetic algorithm, to establish the values of the input parameters used in the training of the neural networks, in order to generate a minimum THR value, which is the output parameter. Since the synthesis of polystyrene particles with different GO concentrations is costly, this research helps to reduce the number of experimental tests and allows to determine the best GO concentration by means of neural models and genetic algorithms.

Kesterite-based copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) thin films have attracted considerable attention as promising materials for sustainable and cost-effective thin-film solar cells. However, the successful integration of these materials into photovoltaic devices is hindered by the coexistence of secondary phases, which can significantly affect device performance and stability. This review article provides a comprehensive overview of recent progress and challenges in controlling secondary phases in kesterite CZTS and CZTSe thin films. Drawing from relevant studies, we discuss state-of-the-art strategies and techniques employed to mitigate the formation of secondary phases. These include a range of deposition methods, such as electrodeposition, sol-gel, spray pyrolysis, evaporation, pulsed laser deposition, and sputtering, each presenting distinct benefits in enhancing phase purity. This study highlights the importance of employing various characterization techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, for the precise identification of secondary phases in CZTS and CZTSe thin films. Furthermore, the review discusses innovative strategies and techniques aimed at mitigating the occurrence of secondary phases, including process optimization, compositional tuning, and post-deposition treatments. These approaches offer promising avenues for enhancing the purity and performance of kesterite-based thin-film solar cells. Challenges and open questions in this field are addressed, and potential future research directions are proposed. By comprehensively analyzing recent advancements, this review contributes to a deeper understanding of secondary phase-related issues in kesterite CZT(S/Se) thin films, paving the way for enhanced performance and commercial viability of thin-film solar cell technologies.

In order to find solutions to current worldwide environmental problems, it is crucial to develop sustainable nanomaterials, ideally with multifunctional properties. Considering this, novel TiO2-SnO2@NMs (noble metals: Au and Ag) composites, for use as sustainable nanomaterials, were successfully prepared via a two-step synthesis process consisting of laser pyrolysis followed by the chemical impregnation of the collected materials with noble metals. The addition of SnO2 favors the transformation of TiO2 from a mixture with a majority Anatase phase to one with a Rutile phase majority. With consideration for their level of environmental toxicity, the features of the synthesized nanomaterials were structurally, morphologically, and optically described and assessed for environmental protection applications as gas sensors and photocatalysts. In the case of the Surface Acoustic Wave sensor, based on a pure TiO2 nanopowder, a notable difference in the frequency shift was detected in comparison to the other examined sensors. All sensors responded to the CH4 concentrations tested (0.02-0.1%). On the other hand, when methyl orange was photodegraded under visible light, the results obtained using NMs for decoration revealed that the photocatalytic activity of TiO2-SnO2@NMs was significantly improved compared to the TiO2-SnO2 binary composite, which already has an enhanced photocatalytic activity, compared to pure TiO2. Overall, this work produces nanoparticles that exhibit better sensory and photocatalytic features, as well as higher levels of biocompatibility with skin cells, for use as eco-friendly nanomaterials for a sustainable future.

In this work, the effects of 60Co y -ray irradiation on high resistivity p -type diodes have been investigated. The diodes were exposed to dose values of 0.1, 0.2, 1, and 2 MGy. Both macroscopic (I-V, C-V) and microscopic investigations, by means of Thermally Stimulated Current (TSC) and Deep Level Transient Spectroscopy (DLTS) techniques, were conducted to characterize the radiation -induced changes. The investigated diodes were manufactured on high resistivity p -type Float Zone (FZ) silicon and were further classified into two types based on the isolation technique between the pad and guard ring: p -stop and p -spray. After irradiation, the macroscopic results of current-voltage and capacitance-voltage measurements were obtained and compared with existing literature data. Additionally, the microscopic measurements focused on the development of the concentration of different radiation -induced defects, including the Boron interstitial -Oxygen interstitial (BiOi) complex, the Carbon interstitial -Oxygen interstitial (CiOi) defect, the H40K, and the so-called I*P. To investigate the thermal stability of induced defects in the bulk, isochronal annealing studies were performed in the temperature range of 100 degrees C to 300 degrees C. These annealing processes were carried out on diodes irradiated with doses of 1 and 2 MGy. Furthermore, in order to investigate the unexpected results observed in the C-V measurements after irradiation with high dose values, the surface conductance between the pad and guard ring was measured as a function of both dose and annealing temperature.

Developing new materials to be applied in extreme environments is an opportunity and a challenge for the future. High entropy alloys are new materials that seem promising approaches to work in nuclear fusion reactors. In this work, FeTaTiVW high entropy alloys were developed and characterized with Molecular Dynamic and Hybrid Molecular Dynamic Monte Carlo simulations. The simulation results show that phase separation originates a lower potential energy per atom and a high level of segregation compared to those of a uniform solid solution. Moreover, the experimental diffractogram of the milled powder shows the formation of a body-centred cubic-type structure and the presence of TiO2. In addition, the microstructure of the consolidated material evidenced three phases: W-rich, Ti-rich, and a phase with all the elements. This phase separation observed in the microstructure agrees with the Hybrid Molecular Dynamic Monte Carlo simulation. Moreover, the consolidated material's thermal conductivity and specific heat are almost constant from 25 degrees C to 1000 degrees C, and linear expansion increases with increasing temperature. On the other hand, specific heat and thermal expansion values are in between CuCrZr and W values (materials chosen for the reactor walls). The FeTaTiVW high entropy alloy evidences a ductile behaviour at 1000 degrees C. Therefore, the promising thermal properties of this system can be attributed to the multiple phases and systems with different compositions of the same elements, which is exciting for future developments.

Tungsten is the primary candidate armour material for the divertor target of the European demonstration fusion power plant. During operation at high temperature, pure tungsten is subject to fracture and recrystallization which results in a loss of strength and worsening of the thermal properties. Additionally, loss-of-coolant accidents with simultaneous air ingress can generate volatile and radioactive tungsten oxides. Advanced W-alloys were developed as alternative and upgrading armour materials of pure tungsten, such as potassium-doped tungsten laminates and self-passivating tungsten alloys. Three mock-ups were manufactured using potassium-doped tungsten laminates, W-10Cr-0.5Y and W-10Cr-0.5Y-0.5Zr as armour materials, each of them consisting of n degrees 4 blocks. The fabrication required optimization and upscaling of the ITER-like process which foresees oxygen-free high conductivity copper as interlayer joined to W-alloy armour block and CuCrZr ITER grade pipe welded to the Cu/W-alloy blocks by hot radial pressing. For quality control of the fabrication steps, non-destructive examination by ultrasonic testing was done on the monoblocks as received, after casting, after hot radial pressing and after high heat flux testing. The results demonstrated that these W-alloys can be used as armour materials of the European demonstration fusion power plant divertor target.

Antidepressant drugs play a crucial role in the treatment of mental health disorders, but their efficacy and safety can be compromised by drug degradation. Recent reports point to several drugs found in concentrations ranging from the limit of detection (LOD) to hundreds of ng/L in wastewater plants around the globe; hence, antidepressants can be considered emerging pollutants with potential consequences for human health and wellbeing. Understanding and implementing effective degradation strategies are essential not only to ensure the stability and potency of these medications but also for their safe disposal in line with current environment remediation goals. This review provides an overview of degradation pathways for amitriptyline, a typical tricyclic antidepressant drug, by exploring chemical routes such as oxidation, hydrolysis, and photodegradation. Connex issues such as stability-enhancing approaches through formulation and packaging considerations, regulatory guidelines, and quality control measures are also briefly noted. Specific case studies of amitriptyline degradation pathways forecast the future perspectives and challenges in this field, helping researchers and pharmaceutical manufacturers to provide guidelines for the most effective degradation pathways employed for minimal environmental impact.

Structurally disordered Pr3+-doped Ca-3(Ta,Ga)(5)O-12 - Pr:CTGG single crystal was grown by the Czochralski technique for the first time and its spectroscopic properties were investigated. Modified Judd-Ofelt analysis was applied to determine spectroscopic and laser emission characteristics. Based on low-temperature absorption and emission spectra, the partial energy levels of Pr3+ ions have been obtained and a multicenter structure of the optical spectra was highlighted. The electron-phonon interactions were also observed in the emission spectra corresponding to the P-3(0) -> H-3(4) transition under different excitation wavelengths. The fluorescence decays of the P-3(0) and D-1(2) levels were measured. The emission cross-sections corresponding to the P-3(0) -> H-3(4) (486.5 nm) and P-3(0) -> F-3(2) (652.7 nm) transitions were found to be sigma(em) = 19 x 10(-20) cm(2) and crem = 15 x 10(-20) cm(2), respectively. The values for other parameters that may predict the possibility of achieving efficient laser emission, especially at 486.5 nm, such as quantum efficiency (eta = 50 %), gain bandwidth (sigma(em) x Iota lambda(eff), = 32.2 x 10(-26) cm(3)), and optical gain (sigma(em) x tau(meas) = 12.86 x 10(-25) cm(2) s) were determined. The obtained results indicate that the Pr:CTGG crystal has a high potential for obtaining efficient laser emission in the blue domain.