Ionizing radiation, especially X-rays and γ photons, are essential in many tools and techniques developed for bioimaging. The most common application regards their use in direct medical imaging such as radiography and tomography. In such applications, the main building blocks of radiation… Read more detectors are scintillating materials, that absorb and down-convert the energy deposited by the incoming ionizing radiation to low-energy UV-Vis-IR light, which is then easily read out by common photodetectors. A valuable class of scintillating materials is represented by rare-earth doped garnets; indeed, garnets in the form of single crystals are already used in some medical instrument and are also promising candidates for Time of Flight Positron Emission Tomography (TOF-PET) detectors where stringent requirements on fast time response are crucial to optimize the spatial localization of the tumours and detection accuracy. Moreover, they can be easily obtained as micro- and nano-sized powders and, in this form, they can be used as phosphors in optical bioimaging. The latter technique consists in the inoculation of the nanoparticles in the tissues to be treated and the imaging occurs through laser-stimulated luminescence in the biological window where tissue absorbance is minimal (700 – 1350 nm). However, this approach presents some drawbacks: the signal monitoring is difficult since excitation and emission lights are close in frequency, and more importantly, the laser power needed is very high and may lead to skin damage and to autofluorescence. The LUMINANCE project aims at the improvement of the scintillation properties of rare-earth doped garnets designed to help the medical community in overcoming two specific needs in bioimaging. Firstly, a new approach in optical bioimaging will be explored by using YAG (Y3Al5O12) nanoparticles doped with near infrared emitting rare earths (Yb, Nd, or Er). This enables the use of low dose x-rays as excitation source instead of lasers, thus eliminating autofluorescence, tissue damages, and detector overexposure. Secondly, we will deepen the structure-property relationships of bulk GGAG (Gd3(Ga,Al)5O12) mixed garnet doped with Ce with the aim of obtaining fast and performing scintillators for TOF-PET detectors. The major strength of the project is the use of rare-earth doped garnet optical ceramics. They can be easily produced with the desired size and shape, not achievable by their single crystal counterparts, but with comparable optical quality, and more affordable costs. Therefore, for the development of YAG nanophosphors, we will use optical ceramics as a transparent testing platform to identify the best doping level and type; on the other hand, we will get performing bulk GGAG as high-quality optical ceramic, also investigating the differences in using nanoparticles or mixed powders as starting materials. Finally, the two proposed solutions will be validated in proof-of-concept experiments.

According to the National Recovery and Resilience Plan (NRRP), part of the Next Generation European Union (NGEU) financial program, the EU aims at accomplishing relevant advancements in the direction of a green revolution, reaching an increment in both technological sustainability… Read more and energetic independence. In this context, photo(electro)chemistry (PEC) is one of the most promising and appealing solar-driven technologies to accomplish the direct photochemical conversion of CO2 (major greenhouse gas from anthropogenic pollutions) into valuable chemicals by performing reduction reactions at the surface of properly functionalized electrodes, in hybrid systems based on light-absorbing semiconductors. The possibility of applying photoactive nanomaterials in PEC strongly depends on their ability to absorb a large portion of the solar spectrum, ensuring an efficient charge separation and interfacial transfer of the photoproduced charge carriers. The more traditional approach requires the continuous modification of tailored materials able to properly guide the reaction selectivity. The recent literature, instead, suggests the possibility of applying different external stimuli, including magnetic field (MF), to overcome some drawback still unsolved, such as detrimental charge recombination. This novel (and poorly studied) approach is extremely promising, especially considering the possibility of modifying electrodes with magnetic nanoparticles to generate a specific magnetic response to MF. To the best of our knowledge, there are only few recent studies describing this possible alternative route, thus fundamental research is needed to understand the basic mechanisms involved in this very specific configuration. Therefore, the main goal of this Project is to unveil potential MF assistance in improving the overall activity of properly designed electrodes to be employed in solar-driven CO2 reduction. In particular, MF-induced variations on efficiency and/or selectivity of this reaction will be investigated as a function of i) the external permanent magnet position and intensity; ii) the possible local MF directly generated by ferrites systems integrated in well consolidated CuxO-TiO2 coupled oxides; iii) the interaction between magnetic responsive ferrites-based component and an externally applied MF. To address the main aims of this Project we set up a relatively young and multidisciplinary consortium made up of scientists with expertise in the synthesis and characterization of photocatalytic materials (Project PI, M.V. Dozzi, UniMi), in the preparation of magnetic inorganic nanomaterials (R. Nisticò, UniMiB), as well as in the advanced characterizations (M.C. Paganini, UniTo), and industrial application of photo(electro)active materials (C. Genovese, UniMe).

The HD-PIT project aims to understand and engineer the processes inducing a phase transition from the diamond cubic (dc) into the hexagonal diamond (hd) phase by nanoindentation of SiGe layers epitaxially grown on Si wafers. The final goal is to realize… Read more hd SiGe pits in the films, which could be subsequently used as a template for the realization of hd SiGe epitaxial dots. Silicon technology drives phenomenal advances in nano-electronics, but the indirect nature of Si bandgap hinders exploitation for photonic integrated circuits. Interestingly, theoretical studies have shown that the hd phase of SiGe, with a relatively high Ge content, turns the alloy into a direct bandgap material. Recently, SiGe with the hd structure has been obtained by epitaxial growth on III-V nanowires. Confirming the predictions, a direct bandgap has been demonstrated. Despite the high potential of these polytypes for photonics, the present synthesis approaches are not fully compatible with Si technology. Another approach based on pressure-induced phase transition has been exploited, obtaining occasionally the Si and Ge hd phase by nanoindentation. However, a clear control of the hd phase appearance in this context is still lacking neither it is verified for SiGe alloys. The project will explore the possibility to realize a controlled and extended transition to the hd phase by nanoindentation of Ge-rich SiGe films, being an optimal solution to obtain desired electronic properties in a system fully integrated into the Si platform. A synergic approach leveraging multiscale atomistic simulations, micro-Raman and electron microscopy experiments, will be used for a rational design of the nanoindentation experiments. In fact, it will allow for an efficient search through the large parameter space that includes a wide range of nanoindentation conditions and many different characteristics of the SiGe films. Because of the high Ge content of the SiGe films, they will be grown under strong out-of-equilibrium conditions on Si substrate by low-energy plasma-enhanced chemical vapour deposition (LEPECVD). While Raman micro-spectroscopy and transmission electron microscopy will be used to assess the formation of the hd phase, the multiscale atomistic simulations will guide the experiments. They will involve first-principle calculations of the electronic, structural, and thermodynamic properties of the hd compounds at the atomic scale, but also larger-scale classical molecular dynamics simulations of the whole indentation process, exploiting state-of-the-art interatomic potential based on machine learning approaches. The project will provide fundamental knowledge to boost the monolith integration of hd group IV compounds for on-chip optical components, such as nano-laser and optical amplifiers, thus enabling optical network-on-chip and being breakthroughs for quantum computing, high performance and green ICT.