Graphene-based interfaces as tuneable support for metal oxide nanoparticles

In my PhD activity I was involved in the study of graphene-supported metal oxide nanoparticles and the effect of the graphene doping on their electronic and chemical properties. Nanostructured materials are nowadays at the centre of the scientific investigation in the condensed matter field. The fundamental concept that drives this research topic is that the microscopic features of a nano-designed material can affect its macroscopic properties. This is the reason why, often, the experimental results lead to applications in many different contexts as for example in chemistry, quantum optics, in the field of energy storage, biosensing or quantum optics, rapidly paving the way towards the developments of new technologies. Nano-architectured materials are strictly related to low dimensionality materials. The term nano, in fact, refers to a length scale at which quantum confinements begins to be non-negligible and it gives rise to microscopic modifications and phenomena that have consequences on the macroscopic behaviour of the system. The building blocks of these structures are typically 2D, 1D and 0D objects i.e., namely, layered materials, nanowires and nanoclusters. In this PhD work I investigated the interaction between nanoparticles and their solid substrate with the aim to tune the properties of the first ones by controlling the structure of the latter. To do so, we combined 2D and 0D materials to fabricate novel nanostructured interfaces. Metal oxides nanoparticles have been studied, with an attention on their possible application as heterogeneous photocatalysts. The thesis starts describing the methods used to create differently nanostructured supports for the metal oxide nanoparticles. Graphene has been used as the key building block in this context because of its several remarkable properties. From the electronic point of view, its outstanding transport properties promise to be an efficient way to increase the charge separation in photocatalytic reactions. On the other hand, its mechanical strength and its thermal stability are two features that a substrate must have to be reliably exploited. In order to modify the electronic structure of graphene, intercalation procedures have been performed to grow a metal oxide thin layer between graphene and its original substrate, whose effect can be described as an electronic doping of graphene. The focus of the experimental activity is the investigation of the correlation between the doping state of graphene and the electronic and chemical properties of the supported particles. Three different metal oxides have been used as both particle constituents and intercalant agents to collect information about different possible graphene doping levels and particles modifications: iron, cobalt and titanium oxide. Synchrotron radiation spectroscopy techniques were used as the principal measurement methods for the characterization of the electronic structure of these interfaces. For titanium oxide, photocatalytic measurements were performed in collaboration with the Department of Chemistry at the University of Trieste, demonstrating that the graphene-based substrate can be designed to enhance the activity of the supported particle-photocatalyst by more than one order of magnitude respect to the same material supported by a metal surface. Theoretical calculations have been also performed to better understand the mechanisms behind this enhancement and possibly predict the behaviour of further nanostructures. In parallel to this research activity I worked on the development and commissioning of a mass-selected nanocluster source, designed to produce clusters with a precise number of atoms in order to exploit space-averaging experimental techniques to investigate their properties. During my PhD period the machine was completed and the first functional tests were performed

Time-dependent density functional theory study of squaraine dye-sensitized solar cells

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Hybrid plasmonic nanostructures based on controlled integration of MoS2 flakes on metallic nanoholes

Here, we propose an easy and robust strategy for the versatile preparation of hybrid plasmonic nanopores by means of controlled deposition of single flakes of MoS2 directly on top of metallic holes. The device is realized on silicon nitride commercial membranes and can be further refined by TEM or FIB milling to achieve the passing of molecules or nanometric particles through a pore. Importantly, we show that the plasmonic enhancement provided by the nanohole is strongly accumulated in the 2D nanopore, thus representing an ideal system for single-molecule sensing and sequencing in a flow-through configuration. Here, we also demonstrate that the prepared 2D material can be decorated with metallic nanoparticles that can couple their resonance with the nanopore resonance to further enhance the electromagnetic field confinement at the nanoscale level. This method can be applied to any gold nanopore with a high level of reproducibility and parallelization; hence, it can pave the way to the next generation of solid-state nanopores with plasmonic functionalities. Moreover, the controlled/ordered integration of 2D materials on plasmonic nanostructures opens a pathway towards new investigation of the following: enhanced light emission; strong coupling from plasmonic hybrid structures; hot electron generation; and sensors in general based on 2D materials. Nanopor

The COMIX polarimeter: a compact device for XUV polarization analysis

We report on the characterization of a novel extreme-ultraviolet polarimeter based on conical mirrors to simultaneously detect all the components of the electric field vector for extreme-ultraviolet radiation in the 45–90 eV energy range. The device has been characterized using a variable polarization source at the Elettra synchrotron, showing good performance in the ability to determine the radiation polarization. Furthermore, as a possible application of the device, Faraday spectroscopy and time-resolved experiments have been performed at the Fe M2,3-edge on an FeGd ferrimagnetic thin film using the FERMI free-electron laser source. The instrument is shown to be able to detect the small angular variation induced by an optical external stimulus on the polarization state of the light after interaction with magnetic thin film, making the device an appealing tool for magnetization dynamics research

Metabolic and anthropometric changes in early breast cancer patients receiving adjuvant therapy

Weight gain and metabolic changes have been related to survival of early breast cancer patients (EBC). ''However, factors influencing metabolism post-diagnosis are not fully understood. We measured anthropometric [body mass index (BMI), body weight, waist and hip circumferences, and waist-to-hip ratio] and metabolic (levels of insulin, glucose, H1Ac, total, HDL, and LDL cholesterol, triglycerides, and the homeostasis model assessment score [HOMA]) parameters in 433 pre- and post-menopausal women with EBC at diagnosis and 3, 6, 9, 12, and 24 months thereafter. At diagnosis, compared with post-menopausal women, pre-menopausal patients were more likely to be leaner and to have a lower BMI, smaller waist and hip circumferences, and waist-to-hip ratio. They had also lower glucose, HbA1c, and triglyceride levels and a lower HOMA score. Furthermore, they were more likely to have an estrogen- and/or progesterone-positive tumor and a higher proliferating breast cancer. During the first two post-diagnosis years, all women showed a significant increase of weight (+0.72 kg/year, P < 0.001), waist circumference (+1.53 cm/year, P < 0.001), and plasma levels of LDL cholesterol (+5.4 mg/dl per year, P = 0.045) and triglycerides (+10.73 mg/dl per year, P = 0.017). In patients receiving chemotherapy only, there was a significant increase in hip circumference (+3.16 cm/year, P < 0.001) and plasma cholesterol levels (+21.26 mg/dl per year, P < 0.001). We showed that weight, body fat distribution, and lipid profile changed in EBC patients receiving adjuvant therapy. These changes occurred during the first 2 years after diagnosis and were not specifically related to chemotherapy, menopausal status, or initial body weight

Excited states in Sm139 described with the interacting boson model plus broken pairs

The high-spin structure of Sm139 has been studied through the Pd110(34S,5n) reaction at beam energies of 150 and 165 MeV. The level scheme has been extended up to an excitation energy of 11.1 MeV and spin 61/2+. A band built on the νi13/2 [660]1/2+ intruder orbital has been established and firmly linked to the known lower-spin levels in the nucleus. The low-lying states of both parities as well as a relatively strong ΔI=1 regular structure observed above spin 27/2- are nicely reproduced by the interacting boson-fermion model with broken pairs