We examine the formation of the solid electrolyte interface (SEI) on anodes made of carbon encapsulated zinc ferrite (ZnFe2O4) nanoparticles (50 nm ZFO-C) as a standard metal oxide electrode ...prototype. The SEI formation and phase evolution are studied by two soft X-ray absorption techniques with different probing depths in the 10–100 nm range and by surface-sensitive X-ray photoemission spectroscopy at several specific capacities of the ZFO-C anodes. These techniques are shown to be able to provide information about the nature and extension of the individual chemical species within the SEI with a typical spatial resolution of 1–5 nm. A peculiar footprint of the interphase formations is obtained by comparing the chemical history of the reactive element sites in the anodes. The progressive development of the SEI in the first cycle and the variety of compositional transformations prior to stabilization are elucidated. Formation of a reversible alkyl carbonate layer, with maximum thickness of 7 nm, is detected at the SEI topmost region. On the basis of these results, we have obtained a map of suitable spatial resolution of the evolution of the different components of the interface layer.
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•Modification of heterogeneous photocatalytic material with gold nanoparticles.•Acetylacetone as reducing agent for the growth of gold nanoparticles (AuNPs).•Samples with different ...wt.% of Au were tested and structurally characterized.•The new Au-TiO2 material showed a lowering of band gap energy.•Photocatalytic kinetic constant for Alizarin Red S degradation was improved.
A new approach to obtain a heterogeneous photocatalytic material with gold nanoparticles and TiO2 semiconductor was performed exploiting the reducing ability of acetylacetone, a chemical present in the TiO2 paste formulation. Gold/TiO2 heterogeneous catalyst supported on polypropylene PP@Au-TiO2A was prepared; composition, structure and morphology of this new material were defined by using UV–Vis spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD), X-ray Fluorescence (XRF), Raman Spectroscopy, Photoluminescence and Diffuse Reflectance Spectroscopy. The new material was tested in the photocatalytic degradation of Alizarin Red S in water solution, as target pollutant, under visible light and correlated with structural and spectroscopic characterizations. PP@Au-TiO2A showed higher photocatalytic activity respect to pure PP@TiO2A with an improvement of photodegradation kinetic. The best performance was obtained using PP@Au-TiO2A sample with 0.006 wt.% of Au and the photocatalytic improvement was correlated with the band gap energy decrease of photocatalyst.
It is well known that the Al2O3 coating of the LiMn2O4 cathodes leads to improvement of the performance of these electrodes. However, the effect of the coating on the fundamental processes occurring ...on the interface with the active material which results in the formation of the solid permeable interphase is yet to be investigated. These effects should be more pronounced in the first cycle when a dynamic interaction of the active material at high voltage with the electrolyte and binder leads to the formation of this passivation layer. Here, we present a detailed investigation of the solid permeable interphase formation in alumina-coated and uncoated LiMn2O4 electrodes using X-ray absorption spectroscopy and analysis on the electrodes at the predesigned charging/discharging states. We demonstrate that the alumina coating leads to modification of the solid permeable layer and its dynamics. We also discuss the possible influences of interface modifications via coating on the battery performance.
After the recent finding that CrI3, displays ferromagnetic order down to its monolayer, extensive studies have followed to pursue new two-dimensional (2D) magnetic materials. In this article, we ...report on the growth of single crystal CrCl3 in the layered monoclinic phase. The system after mechanical exfoliation exhibits stability in ambient air (the degradation occurs on a time scale at least four orders of magnitude longer than is observed for CrI3). By means of mechanical cleavage and atomic force microscopy (AFM) combined with optical identification, we demonstrate the systematic isolation of single and few layer flakes onto 270 nm and 285 nm SiO2/Si (100) substrates with lateral size larger than graphene flakes isolated with the same method. The layer number identification has been carried with statistically significant data, quantifying the optical contrast as a function of the number of layers for up to six layers. Layer dependent optical contrast data have been fitted within the Fresnel equation formalism determining the real and imaginary part of the wavelength dependent refractive index of the material. A layer dependent (532 nm) micro-Raman study has been carried out down to two layers with no detectable spectral shifts as a function of the layer number and with respect to the bulk.
The seasonal and year-to-year variability of the phytoplankton size class (PSC) spatial distribution has been examined in the Mediterranean Sea by using the entire time series of Sea-viewing Wide ...Field-of-view Sensor (SeaWiFS) space observations (1998-2010). Daily maps of PSCs have been determined using an empirical model based on a synoptic relationship between surface chlorophyll a and diagnostic pigments referred to different taxonomic groups. The analysis of micro-, nano- and pico-phytoplankton satellite time series (1998-2010) describes, quantitatively, the algal assemblage structure over the basin and reveals that the main contribution to chlorophyll a in most of the Mediterranean Sea comes from the pico-phytoplankton component, especially in nutrient-poor environments. Regions with different and peculiar features are the Northwestern Mediterranean Sea, the Alborán Sea and several coastal areas, such as the North Adriatic Sea. In these areas, local interactions between physical and biological components modulate the composition of the three phytoplankton size classes. It results that, during the spring bloom season, micro-phytoplankton dominates in areas of intense vertical winter mixing and deep/intermediate water formation, while in coastal areas micro-phytoplankton dominates in all seasons because of the nutrient supply from the terrestrial inputs. In the Alborán Sea, where the Atlantic inflow modulates the nutrient availability, any predominance of one class over the other two has been observed. The nano-phytoplankton component instead remains widespread over the entire basin along the year, and its contribution to chlorophyll a is of the order of 30-40 %. The largest inter-annual signal occurs in the Northwestern Mediterranean Sea, driven by the year-to-year variation in intensity and extension of the spring bloom, followed by the Alborán Sea, in which the inter-annual variability is strongly modulated by the Atlantic inflow. In absence of sufficient in situ data of community composition, the satellite-based analysis demonstrated that pico-, nano- and micro-phytoplankton classes often coexist. The predominance of one group over the other ones is strongly dependent on the physical and biological processes occurring at the mesoscale. These processes directly influence the nutrient and light availability, which are the principal forcing for the algae growth.
FERMI@Elettra is a free electron-laser (FEL)-based user facility that, after two years of commissioning, started preliminary users' dedicated runs in 2011. At variance with other FEL user facilities, ...FERMI@Elettra has been designed to deliver improved spectral stability and longitudinal coherence. The adopted scheme, which uses an external laser to initiate the FEL process, has been demonstrated to be capable of generating FEL pulses close to the Fourier transform limit. We report on the first instance of FEL wavelength tuning, both in a narrow and in a large spectral range (fine- and coarse-tuning). We also report on two different experiments that have been performed exploiting such FEL tuning. We used fine-tuning to scan across the 1s-4p resonance in He atoms, at 23.74 eV (52.2 nm), detecting both UV-visible fluorescence (4p-2s, 400 nm) and EUV fluorescence (4p-1s, 52.2 nm). We used coarse-tuning to scan the M4,5 absorption edge of Ge (∼29.5 eV) in the wavelength region 30-60 nm, measured in transmission geometry with a thermopile positioned on the rear side of a Ge thin foil.
Abstract
Ultrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM,
...$$\lambda $$
λ
= 400 nm) as a pump and broadband 340–780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/
$$\hbox {cm}^2$$
cm
2
for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the
$$E_1$$
E
1
,
$$E_1+\Delta $$
E
1
+
Δ
singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.
The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The ...optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation.
Pristine LiMn2O4, synthetized by solid-state route, is coated by an Al2O3 layer through co-precipitation method, in order to enhance the electrochemical performances and stability of the cathode, ...especially at high temperatures. Structural analysis by X-ray diffraction and morphological characterization by scanning and transmission electron spectroscopy reveal phase pure and crystalized nanomaterial forming clusters.
The cycling performances of pristine and modified materials are investigated by galvanostatic cycles at several charge/discharge rates. A detailed analysis of the interfacial properties, and of their impact toward cycling behavior, is carried out by combining galvanostatic cycles at 1C and electrochemical impedance spectroscopy at T=25°C and T=50°C. The results show that the electrode/electrolyte interface of Al2O3-modified LiMn2O4 is stabilized by suppressing Mn dissolution, resulting in improved cycleability, especially at high temperatures. These results are corroborated by X-ray photoelectron spectroscopy studies, which confirm the suppression of Mn dissolution for the Al2O3–coated material.
•LiMn2O4 is coated by Al2O3 via co-precipitation method..•The coated material exhibit enhanced cycling performance..•A stable interfacial behavior is revealed by electrochemical impedance spectroscopy.•XPS measurements confirm suppression of Mn dissolution.
A
bstract
The quantum interference between the decays of entangled neutral kaons is studied in the process
ϕ
→ K
S
K
L
→
π
+
π
−
π
+
π
−
, which exhibits the characteristic Einstein-Podolsky-Rosen ...correlations that prevent both kaons to decay into
π
+
π
−
at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and
CPT
violation effects, which may be justified in a quantum gravity framework.
The analysed data sample was collected with the KLOE detector at DAΦNE, the Frascati
ϕ
-factory, and corresponds to an integrated luminosity of about 1.7 fb
−
1
, i.e. to about 1
.
7 × 10
9
ϕ
→ K
S
K
L
decays produced. From the fit of the observed ∆
t
distribution, being ∆
t
the difference of the kaon decay times, the decoherence and
CPT
violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses.
The results are consistent with no deviation from quantum mechanics and
CPT
symmetry, while for some parameters the precision reaches the interesting level at which — in the most optimistic scenarios — quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.
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