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Thermochemical H2O/CO2 splitting is considered one of the most appropriate solution technologies for the sustainable and environmentally friendly production of H2 and CO. The two steps process is the most promising technology: in the former the solar-driven endothermic reduction of metal oxides occurs, that in latter exothermic step are re-oxidated by water or carbon dioxide giving syngas and re-generating the catalyst. The "ideal" metal oxide should be able to optimise both steps allowing to occur at the lowest temperature the oxidation and the reduction. The ceria-zirconia systems (CeO2-ZrO2) seem to outperform the materials developed to date, even if the working temperatures are still too high. In this work, CeO2-ZrO2 based materials containing suitable dopants were prepared using hydrothermal and co-precipitation techniques in order to lower the oxidation/reduction temperatures. The developed materials were characterised (BET; XRD...) and their activity was tested by TG analysis and in a lab-scale reactor. The results show that a ceria zirconia sample prepared by hydrothermal method shows the best redox properties. Furthermore, the doping allows to lower the working temperatures

INTRODUCTION: The clinical applications of fluorine-18-deoxyglucose Positron Emission Tomography (FDG PET) have been proposed on account of experimental evidence of increased glucose metabolism in tumor cells. MATERIAL AND METHODS: We examined 98 lymphoma patients--33 with Hodgkin and 65 with non-Hodgkin disease--with FDG PET and compared its findings with those of clinical and conventional radiologic studies. FDG PET was also used to follow-up 32 patients and the results were once again compared with clinical and radiologic data. RESULTS: During staging, 138 lesions were found, 82 of them (59%) in nodal and 56 (41%) in extranodal locations. Extranodal tumor sites were found in 39 patients (40%), namely 4 with Hodgkin (12%) and 35 with non-Hodgkin (54%) disease. FDG PET findings were in agreement with clinical and radiologic results in all nodal and extranodal lesions, since all of them exhibited abnormally increased FDG uptake. PET detected new tumor sites in 6 patients. In the follow-up, agreement was observed in the majority (78%) of lesions, 30 of them in complete regression, 15 in partial regression and 17 in progression; however, the diagnostic results were in disagreement in the remaining (22%) tumor sites: no abnormal FDG uptake was found in 9 cases despite the persistence of radiologic abnormalities (post-treatment fibrosclerosis). Slightly increased FDG uptake (residual disease) was found in the other 8 lesions, where there was no clinical and/or radiologic evidence of disease. CONCLUSIONS: FDG PET is a functional imaging technique useful to diagnose lymphomas and providing metabolic characterization of cancer abnormalities. Whole body PET permits the simultaneous assessment of nodal and extranodal lymphoma localizations. During the follow-up, FDG PET permits better monitoring of treatment effects than clinical and radiologic examinations.

The catalytic and electro-optical properties of TiO2-based materials depend on the defectivity of their electronic structures and in turn on the synthesis conditions. It is however less clear how t...

Stimulated Raman scattering in transparent glass-ceramics (TGCs) based on bulk nucleating phase Ba2NaNb5O15 were investigated with the aim to explore the influence of micro- and nanoscale structural transformations on Raman gain. Nanostructured TGCs were synthesized, starting with 8BaO·15Na2O·27Nb2O5·50SiO2 (BaNaNS) glass, by proper nucleation and crystallization heat treatments. TGCs are composed of nanocrystals that are 10–15 nm in size, uniformly distributed in the residual glass matrix, with a crystallinity degree ranging from 30 up to 50% for samples subjected to different heat treatments. A significant Raman gain improvement for both BaNaNS glass and TGCs with respect to SiO2 glass is demonstrated, which can be clearly related to the nanostructuring process. These findings show that the nonlinear optical functionalities of TGC materials can be modulated by controlling the structural transformations at the nanoscale rather than microscale.

Amorphous catalytic materials belonging to the Nb2O5–P2O5–SiO2 system were prepared through an original sustainable sol-gel procedure, and characterized by surface area, porosity and acidity measurements. Their acid properties have been investigated by FT-IR spectroscopy of adsorbed pyridine, ammonia titration and TPR, as well as by titration with 2-phenylethylamine from organic solution. They present Lewis acidity attributed to niobium surface cationic centers, and Brønsted acidity sufficiently strong to protonate pyridine. The total acidity depends on the niobium content. The conversion of ethanol was investigated by vapor phase Temperature Programmed Reaction, steady-state catalytic experiments and static In Situ FTIR experiments. The samples are active in converting ethanol to ethylene with 100% selectivity at low conversion (523–573 K), but also produce acetaldehyde by dehydrogenation at higher temperature and conversion. They show an unusually poor activity for the production of diethylether also at low ethanol conversion. Ethoxy groups act as reaction surface intermediates.

The functional properties of metal oxide semiconductors depend on intrinsic and extrinsic defects. The population of intrinsic defects is strongly affected by the synthesis method and subsequent treatments of the material, while extrinsic defects can originate from suitable doping. Stoichiometric ZrO2 is a nonreducible oxide with a large band gap. Therefore, controlling and modulating its defect profile to induce energy states in the band gap is the sole possibility to make it a photocatalyst responsive to visible light. We report a method, based on low temperature sol−gel synthesis coupled with treatments performed in mild conditions, to obtain undoped visible light-responsive ZrO2−x. The electronic structure of these materials is interpreted in relation to their oxygen vacancy defect population. On the basis of a wide set of experimental measurements (X-ray photoelectron, steady-state and time-resolved photoluminescence, electron paramagnetic resonance, and UV−visible diffuse reflectance spectroscopy) and supported by density functional theory calculations, we demonstrate, for the first time, the predominance of positively charged F-center oxygen vacancies that do not give rise to Zr3+ species.

Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is considered one of the most widespread emerging contaminants. Its incidence in water can favor the growth of drug-resistant bacteria and harm aquatic organisms endangering both the human health and the ecosystem. Advanced oxidation processes (AOPs) based on the action of reactive oxygen species are very effective technologies for the removal of this contaminant from water. In this context, ZnO is one of the most studied semiconductors for photocatalytic water treatment. In this work, the photocatalytic activity of fluorine-doped ZnO nano- and meso-crystals synthesized by a hydrothermal approach is reported, exploring the role of a low F atomic concentration (0.25, 0.5 and 1 at. %) on the degradation of DCF in comparison with bare ZnO. All doped samples show high rates of DCF degradation and mineralization, which were realized primarily thanks to their high efficiency in the generation of hydroxyl radicals ( OH). The property-structure-function relationships of the materials are investigated by complementary techniques, such as SEM, XRD, EPR, UV–vis DRS and PL, with the aim to evaluate the role of fluorine in determining their morphological, electronic and optical properties.

Hydrogen production by photocatalytic water splitting is one of the most promising sustainable routes to store solar energy in the form of chemical bonds. To obtain significant H2 evolution rates (HERs) a variety of defective TiO2 catalysts were synthesized by means of procedures generally requiring highly energy-consuming treatments, e.g. hydrogenation. Even if a complete understanding of the relationship between defects, electronic structure and catalytic active sites is far from being achieved, the band gap narrowing and Ti3+-self-doping have been considered essential to date. In most reports a metal co-catalyst (commonly Pt) and a sacrificial electron donor (such as methanol) are used to improve HERs. Here we report the synthesis of TiO2/C bulk heterostructures, obtained from a hybrid TiO2-based gel by simple heat treatments at 400 °C under different atmospheres. The electronic structure and properties of the grey or black gel-derived powders are deeply inspected by a combination of classical and less conventional techniques, in order to identify the origin of their photoresponsivity. The defective sites of these heterostructures, namely oxygen vacancies, graphitic carbon and unpaired electrons localized on the C matrix, result in a remarkable visible light activity in spite of the lack of band gap narrowing or Ti3+-self doping. The materials provide HER values ranging from about 0.15 to 0.40 mmol h−1 gcat−1, under both UV- and visible-light irradiation, employing glycerol as sacrificial agent and without any co-catalyst.

The development of a simple, economic and low-temperature synthesis procedure for titanium oxide thin films is an important challenge, due to their diffusion and to the limitations imposed by high temperature annealing. The knowledge on the properties of amorphous TiO2 films, as well as on the effect of their functionalization by organic compounds, is still inadequate. Here we describe a hydrolytic sol-gel procedure to prepare TiO2-based hybrid (inorganic-organic) thin films containing four different complexing agents in their structure (acetylacetone, dibenzoylmethane, citric acid and diethanolamine). The process variables were explored in order to attain stable sols and to tune the features of the amorphous films resulting by drying at 80 °C. Their structural, morphological, optical and electrical properties were studied by SEM, AFM, XRD, ellipsometry, FT-IR and UV–vis-NIR spectroscopy and resistivity measurements. The effect of the organic component, precursors concentration, deposition parameters and annealing temperature was considered. Moreover, the modifications induced by the exposure of the hybrid films to UV light were deeply investigated. A short UV treatment has a strong impact on the microstructure and wettability of the films and promotes a striking increase in their electrical conductivity.

Thermochemical cycles received renewed interest as CO2 and H2O energy-upgrading processes using solar energy as source. The two-step cycles, based on self-reduction in a solar reactor at high temperature (above 1300–1400 °C) and re-oxidation by CO2 and/or H2O flow, are the most interesting due to their simplicity and high theoretical solar-to-fuel efficiency. In the two-step cycle, ceria has been recognized as the benchmark material but it suffers from high reduction temperature, low re-oxidation kinetics as well as low stability, thus hindering practical application. In this work, the redox properties of two Ce0.75Zr0.25O2 materials prepared by hydrothermal synthesis were compared with those of a co-precipitated sample with the same nominal composition used as reference. Samples were characterized by X-Ray Diffraction (XRD), N2 physisorption, Scanning Elecron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and Electron Paramagnetic Resonance (EPR); their self-reducibility and CO2 splitting activity were tested in a Thermogravimetric (TG) balance, while H2O splitting properties were studied in an ad-hoc fixed bed reactor on H2 pre-reduced samples. Characterization results and activity tests agreed that the Ce3+ fraction both on the surface and in the bulk of ceria-zirconia can be increased by hydrothermal synthesis, thus providing improved redox properties and higher splitting activity with respect to the co-precipitated sample. So, hydrothermal synthesis, providing a controlled nucleation and growth of crystallites, appears as a promising route for the preparation of ceria-based materials with tuned oxygen vacancies.

A TiO2–based hybrid material (HSGT), obtained by a sol–gel route wholly performed in air at room temperature, was used as catalyst for the oxidative degradation of 2,4-dichlorophenol (2,4-DCP), 4- chlorophenoxyacetic acid (4-CPA) and phenanthrene (PHE). Acetylacetonate ligands, used as complexing/sensitizing molecules, was added directly to the solution containing the precursors of titanium. In the presence of air, the acetylacetonate ligands on the HSGT surface were able to generate stable superoxide radicals, as demonstrated by EPR measurements. The presence of superoxide radicals correlated to the catalytic activity of HSGT. ThDue to the stability of the free radicals, HSGT can be considered a promising catalyst for the degradation of organic pollutants.

A series of TiO2-based hybrid inorganic–organic materials was synthesized by sol–gel and characterized by thermal and spectroscopic techniques. The xerogels have an amorphous structure, with part of Ti4+ ions stably coordinated to acetylacetonate ligands. Ligand-to metal charge transfer results in an extended light absorption in the visible range, with a significant reduction of the band gap compared to the reference TiO2. The hybrid structure is also related to the unusual presence of superoxide radical anions stably adsorbed on the materials surface. These properties make the studied materials active in the degradation of organic pollutants: their catalytic efficiency was tested in the removal of 2,4-dichlorophenol from water without light irradiation.

Hybrid sol–gel TiO2–acetylacetonate (HSGT) material has been synthesized via a sol–gel route. The as dried HSGT can be described as an amorphous polymeric network of titanium oxo-clusters on which surface part of Ti4+ ions are involved in strong complexation with acetylacetonate (acac) ligands. In this material a ligand-to-metal charge transfer (LMCT) is active giving light absorption in the visible region indicating a band gap of 2.5 eV, lower than crystalline TiO2. In the HSGT gel derived material the LMCT mechanism results much more active respect to ligands on crystalline nanoparticles. In presence of air, the acac ligands on the HSGT surface are able to generate and stabilize superoxide radical as resulting by EPR measurements. The ˙O2− radicals were stably adsorbed on the HSGT at room temperature for very long time. The presence of these free radicals makes HSGT material a useful catalyst in degradation of organic pollutants. Its catalytic activity has been tested in the oxidative degradation of phenanthrene resulting in a fast degradation rate in absence of any light irradiation.

OBJECTIVE: The aim of this study was to differentiate benign from malignant adrenal tumors using positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in patients with unilateral adrenal masses originally detected by CT or MR imaging. CONCLUSION: PET imaging with FDG can metabolically characterize adrenal masses. Abnormally increased FDG uptake in adrenal malignancies allows one to differentiate these abnormalities from benign lesions. Whole-body PET can also reveal extraadrenal tumor sites in patients with malignant tumors, using a single imaging technique for accurate disease staging.