'School adopts an experiment': the photoluminescence in extra-virgin olive oil and in tonic water

We report a laboratory activity, carried out along with high- and secondary-school students, that can be done to increase the interest of the young in scientific studies. Groups of selected students 'adopted' experiments at physics research laboratories, under the guidance of university researchers. Subsequently, the students demonstrated the experiments to the public at large during the annual science festival organized in Palermo by the association PalermoScienza, in collaboration with the University of Palermo. Experiments on the magnetic levitation of superconductors and on the photoluminescence of several substances were proposed. We discuss the experiment on photoluminescence as a case study. The students who adopted the experiments reinforced their commitment to learning. They acquired a physics-based knowledge of the topics connected with the experiments in a much better way compared with the usual didactics in school

Chapter Mostrare l’invisibile: il soffitto trecentesco nascosto del convento di Santa Caterina a Palermo

The 43rd UID conference, held in Genova, takes up the theme of ‘Dialogues’ as practice and debate on many fundamental topics in our social life, especially in these complex and not yet resolved times. The city of Genova offers the opportunity to ponder on the value of comparison and on the possibilities for the community, naturally focused on the aspects that concern us, as professors, researchers, disseminators of knowledge, or on all the possibile meanings of the discipline of representation and its dialogue with ‘others’, which we have broadly catalogued in three macro areas: History, Semiotics, Science / Technology. Therefore, “dialogue” as a profitable exchange based on a common language, without which it is impossible to comprehend and understand one another; and the graphic sign that connotes the conference is the precise transcription of this concept: the title ‘translated’ into signs, derived from the visual alphabet designed for the visual identity of the UID since 2017. There are many topics which refer to three macro sessions: - Witnessing (signs and history) - Communicating (signs and semiotics) - Experimenting (signs and sciences) Thanks to the different points of view, an exceptional resource of our disciplinary area, we want to try to outline the prevailing theoretical-operational synergies, the collaborative lines of an instrumental nature, the recent updates of the repertoires of images that attest and nourish the relations among representation, history, semiotics, sciences

Survey on European Studies of the Chemical Characterisation of Tattoo Ink Products and the Measurement of Potentially Harmful Ingredients

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Photoluminescence of Carbon Dots Embedded in a SiO2 Matrix

We synthetized carbon dots by a pyrolitic method, and studied their photoluminescence in aqueous environment and upon trapping in a solid matrix. To this aim, we devised a facile procedure allowing to embed the dots in amorphous SiO2, without the need of any pre-functionalization of the nanoparticles, and capable of yielding a brightly photoluminescent monolith. Experimental data reveal a remarkable similarity between the emission properties of carbon dots in water and in SiO2, suggesting that the chromophores responsible of the photoluminescence undergo only weak interactions with the environment. Time-resolved photoluminescence data reveal that the typical photoluminescence tunability of these dots mostly arises, in the present case, from the co-existence of two independent emission bands. These two signals have different emission peak positions (2.8-2.9 and 2.2-2.3 eV respectively) and decay lifetimes (7.0 and 9.0 ns respectively), while their intensity ratio is controlled by the excitation wavelength

Characterization of cesium and H-/D- density in the negative ion source SPIDER

The Heating Neutral Beam Injectors (HNBs) for ITER will have to deliver 16.7 MW beams of H/D particles at 1 MeV energy. The beams will be produced from H-/D- ions, generated by a radiofrequency plasma source coupled to an ion acceleration system. A prototype of the ITER HNB ion source is being tested in the SPIDER experiment, part of the ITER Neutral Beam Test Facility at Consorzio RFX. Reaching the design targets for beam current density and fraction of coextracted electrons is only possible by evaporating cesium in the source, in particular on the plasma facing grid (PG) of the acceleration system. In this way the work function of the surfaces decreases, significantly increasing the amount of surface reactions that convert neutrals and positive ions into H-/D-. It is then of paramount importance to monitor the density of negative ions and the density of Cs in the proximity of the PG. Monitoring the Cs spatial distribution along the PG is also essential to guarantee the uniformity of the beam current. In SPIDER, this is possible thanks to the Cavity Ringdown Spectroscopy (CRDS) and the Laser absorption Spectroscopy diagnostics (LAS), which provide line-integrated measurements of negative ion density and neutral, ground state Cs density, respectively. The paper discusses the CRDS and LAS measurements as a function of input power and of the magnetic and electric field used to reduce the coextraction of electrons. Negative ion density data are in qualitative agreement with the results in Cs-free conditions. In agreement with simulations, Cs density is peaked in the center of the source; a top/bottom non uniformity is however present. Several effects of plasma on Cs deposition are presented.Comment: 17 pages, 9 figures. Paper (Preprint) following the poster contribution at the SOFT 2022 conference. The destination journal is Fusion Engineering and Desig

Properties of HO2• radicals induced by γ-ray irradiation in silica nanoparticles

We report an experimental investigation on the effects of γ-ray irradiation in several types of silica nanoparticles previously loaded with O2 molecules. They differ in specific surface and average diameter. By electron paramagnetic resonance (EPR) measurements we observe the generation of about 1018 HO2•/cm3 interstitial radicals. These radicals are induced by reaction of interstitial O2 molecules with radiolytic H atoms, as previously suggested for O2-loaded bulk a-SiO2 samples. However, at variance with respect to bulk materials, our experimental evidences suggest a different generation process of HO2• radical. In fact, by a detailed study of samples exposed to D2O, our results prove that radiolytic hydrogen atoms reacting with O2 to produce HO2• mainly arise from a radiation induced breaking of H2O molecules in the layers surrounding the nanoparticles or in the interstices. Also, by the correlation of HO2• paramagnetic centers concentration, determined by EPR measurements, and O2 Raman/PL signal we further considered the issue of the direct estimation of the O2 concentration in silica nanoparticles from Raman/PL spectra giving an independent conversion factor (the ratio between these latter two quantities), which is in good agreement with those previously proposed by other authors basing on optical measurements

Structure effects induced by high mechanical compaction of STAM-17-OEt MOF powders

Financial support by PJ-RIC-FFABR_2017 and the EPSRC grant EPSRC industrial CASE award (grant EP/N50936X/1) are acknowledged. The research programme Nanoporous materials (P1-0021) financially supported by Slovenian Research Agency (ARRS) is acknowledged as well.Metal-organic frameworks (MOFs) are promising materials for many potential applications, spacing from gas storage to catalysis. However, the powder form of which they are generally made is not suitable, mainly because of the low packing density. Powder compaction is therefore necessary, but also challenging because of their typical mechanical fragility. Indeed, generally, they undergo irreversibly damages upon densification processes, for example partially or totally loosing microporosity and catalytic activity. In this work, we deeply study the compaction effects on the flexible Cu(II)-based MOF STAM-17-OEt  (Cu(C10O5H8)1.6 H2O), whose chemical composition is close to that of HKUST-1, obtaining that it is, by contrast, extremely suitable for mechanical compaction processes with pressures up to 200 MPa, which increase its packing density, its catalytic activity, and preserve porosity, flexibility and water stability, characteristics of STAM-17-OEt. The results are supported by many experimental techniques including EPR spectroscopy, PXRD diffraction, CO2 isotherms studies and catalytic tests.Publisher PDFPeer reviewe

Direct sunlight facility for testing and research in HCPV

A facility for testing different components for HCPV application has been developed in the framework of “Fotovoltaico ad Alta Efficienza” (FAE) project funded by the Sicilian Regional Authority (PO FESR Sicilia 2007/2013 4.1.1.1). The testing facility is equipped with an heliostat providing a wide solar beam inside the lab, an optical bench for mounting and aligning the HCPV components, electronic equipments to characterize the I-V curves of multijunction cells operated up to 2000 suns, a system to circulate a fluid in the heat sink at controlled temperature and flow-rate, a data logging system with sensors to measure temperatures in several locations and fluid pressures at the inlet and outlet of the heat sink, and a climatic chamber with large test volume to test assembled HCPV modules

The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions

Fluorescent Carbon Nanodots as Sensors of Toxic Metal Ions and Pesticides

Carbon nanodots (CDs) are a new class of fluorescent carbon-based nanomaterials characterized by a plethora of morphologies and sizes. Among these, we can include two different types of CDs, namely, graphitic and diamond-like. This wide range of structures opens up the possibility to design different CDs, with tunable optical properties accordingly to the synthesis method and precursors used. We prepared two different CDs following a bottom-up approach by thermally induced decomposition of organic precursors (namely, citric acid and urea in different molar ratios), and using purification by Size Exclusion Chromatography (SEC). Obtained CDs were characterized by Raman, absorption and fluorescence (PL) spectroscopies to understand structural and optical properties, and by atomic force microscopy (AFM) to elucidate morphology. They feature graphitic and diamond-like carbon structures with highly efficient visible emissions. Their sensing towards Cd and Hg heavy metals has been tested by PL experiments. We found a PL quenching in the presence of concentrations of metal salts starting from 0.5 μM and a selectivity towards the interacting ions, depending on the CDs structure, enabling using them for sensing. Furthermore, preliminary experiments suggest that these dots can also be used in principle as sensors of common pesticides. Considering the advantages of carbon dots with respect to other nanomaterials, such as non-toxicity, low cost and ease of synthesis, we consider these results to be very promising in view of exploiting the optical response of carbon dots to fabricate in the near future a variety of pollutant-sensing devices