Adhesion, mobility and aggregation of nanoclusters at surfaces: Ni and Ag on Si, HOPG and graphene

Abstract: An experimental investigation of Ag and Ni nanoparticles (NPs) deposited on Silicon with its native oxide, on highly oriented pyrolytic graphite and on graphene flakes is reported. The NPs were physically synthesized with a magnetron based gas aggregation source and the produced beam was mass-filtered and deposited in vacuum on the substrates. The study was concentrated on the morphology for the different cases, shedding some light on the interaction of pre-formed NPs with surfaces, a crucial aspect both of technological and scientific relevance. The nature of adhesion can be strongly influenced by the intrinsic properties of the surface (like for instance the energetics of interaction between the NP surface atoms and the first layers of the substrate) and/or the extrinsic properties, like the presence of defects, step edges, impurities and other irregularities. After adhesion, the NPs mobility and their mutual interaction are very relevant. In this work, the study was concentrated on NP/surface morphology, by using atomic force microscopy, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Article highlights: Morphology of physically synthesized metal Nano-Particles (NPs) on Si, HOPG and Graphene was investigated. The NPs were pure Ag and Ni. Coalescence, diffusion and self-aggregation and preferential adhesion were observed, with possible applications in sensor technology.Possible explanations are: NP softness, NP/surface bonding interaction and presence of contaminant species molecules between NP

Optical and electronic properties of silver nanoparticles embedded in cerium oxide

Wide bandgap oxides can be sensitized to visible light by coupling them with plasmonic nanoparticles (NPs). We investigate the optical and electronic properties of composite materials made of Ag NPs embedded within cerium oxide layers of different thickness. The electronic properties of the materials are investigated by X-ray and ultraviolet photoemission spectroscopy, which demonstrates the occurrence of static charge transfers between the metal and the oxide and its dependence on the NP size. Ultraviolet-visible spectrophotometry measurements show that the materials have a strong absorption in the visible range induced by the excitation of localized surface plasmon resonances. The plasmonic absorption band can be modified in shape and intensity by changing the NP aspect ratio and density and the thickness of the cerium oxide film

Effect of Dietary Supplementation with Eufortyn® Colesterolo Plus on Serum Lipids, Endothelial Reactivity, Indexes of Non-Alcoholic Fatty Liver Disease and Systemic Inflammation in Healthy Subjects with Polygenic Hypercholesterolemia: The ANEMONE Study. Nutrients. 2022 May 18;14(10):209

We aimed to evaluate if dietary supplementation with a nutraceutical compound (Eufortyn® Colesterolo Plus) containing standardized bergamot polyphenolic fraction phytosome (Vazguard®), artichoke extract (Pycrinil®), artichoke dry extract. (Cynara scolymus L.), Q10 phytosome(Ubiqosome®) and zinc, could positively affect serum lipids concentration, systemic inflammation and indexes of non-alcoholic fatty liver disease (NAFLD) in 60 healthy subjects with polygenic hypercholesterolemia. Participants were adhering to a low-fat, low-sodium Mediterranean diet for a month before being randomly allocated to 8-week treatment with 1 pill each day of either Eufortyn® Colesterolo Plus or placebo. Dietary supplementation with Eufortyn® Colesterolo Plus was associated with significant improvement in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), high-sensitivity C-reactive protein (hs-CRP) and endothelial reactivity (ER) in comparison with baseline, and with significant reductions in waist circumference, TC, LDL-C, LDL-C/HDL-C, lipid accumulation product and fatty liver index compared to placebo. The study shows that dietary supplementation with standardized bergamot polyphenolic fraction phytosome, artichoke extracts, Q10 phytosome and zinc safely exerts significant improvements in serum lipids, systemic inflammation, indexes of NAFLD and endothelial reactivity in healthy subjects with moderate hypercholesterolemia

Ultrafast Formation of Small Polarons and the Optical Gap in CeO2

The ultrafast dynamics of excited states in cerium oxide are investigated to access the early moments of polaron formation, which can influence the photocatalytic functionality of the material. UV transient absorbance spectra of photoexcited CeO2 exhibit a bleaching of the band edge absorbance induced by the pump and a photoinduced absorbance feature assigned to Ce 4f → Ce 5d transitions. A blue shift of the spectral response of the photoinduced absorbance signal in the first picosecond after the pump excitation is attributed to the dynamical formation of small polarons with a characteristic time of 330 fs. A further important result of our work is that the combined use of steady-state and ultrafast transient absorption allows us to propose a revised value for the optical gap for ceria (Eog = 4 eV), significantly larger than usually reported

Injecting Electrons into CeO2 via Photoexcitation of Embedded Au Nanoparticles

The electron injection efficiency and the steady state absorptance at different photon energies for a composite system made of Au NPs embedded in a cerium oxide matrix are reported. Cerium oxide can be coupled with plasmonic nanoparticles (NPs) to improve its catalytic properties by visible-light absorption. The present work is a study of the ultrafast dynamics of excited states induced by ultraviolet and visible-light excitation in Au NPs combined with cerium oxide, aimed at understanding the excitation pathways. The data, obtained by femtosecond transient absorption spectroscopy, show that the excitation of localized surface plasmon resonances (LSPRs) in the Au NPs leads to an ultrafast injection of electrons into the empty 4f states of the surrounding cerium oxide. Within the first few picoseconds, the injected electrons couple with the lattice distortion forming a polaronic excited state, with similar properties to that formed after direct band gap excitation of the oxide. At sub-picosecond delay times, we observed relevant differences in the energetics and the time dynamics as compared to the case of band gap excitation of the oxide. Using different pump energies across the LSPR-related absorption band, the efficiency of the electron injection from the NPs into the oxide was found to be rather high, with a maximum above 30%. The injection efficiency has a different trend in energy as compared to the LSPR-related static optical absorptance, showing a significant decrease in low energies. This behavior is explained considering different deexcitation pathways with variable weight across the LSPR band. The results are important for the design of materials with high overall solar catalytic efficiency

Self-Reported Coffee Consumption and Central and Peripheral Blood Pressure in the Cohort of the Brisighella Heart Study.

Even though coffee consumption has been clearly related to a number of benefits to the cardiovascular system, its effect on blood pressure (BP) has not been fully elucidated. In this sub-analysis of the Brisighella Heart Study (BHS), we compared central and peripheral BP values in a sub-cohort of 720 men (47.9%) and 783 women (52.1%) reporting the drinking of different amounts of coffee each day, for whom a full set of clinical, laboratory and hemodynamic parameters was available. According to our observations, moderate coffee drinking was associated to either higher levels of systolic BP (SBP) compared to those with heavy coffee consumption or lower SBP than that in the non-coffee drinking group (p-value for trend <0.05). In particular, people who drank 2 cups of coffee per day and people who drank >3 cups per day had lower SBP than non-coffee drinkers by 5.2 ± 1.6 mmHg (p = 0.010) and 9.7 ± 3.2 mmHg, respectively (p = 0.007). Similar trends were also observed for peripheral pulse pressure (PP), aortic BP and aortic PP. In the age-adjusted multiple linear regression model, negative predictors of SBP, PP, aortic BP and aortic PP were the estimated glomerular filtration rate (eGFR), female sex and coffee consumption. Positive predictors included body mass index (BMI) and low-density lipoprotein cholesterol (LDL-C). Then, our findings show that regular coffee drinking is associated with lower SBP, PP, aortic BP and aortic PP, but with similar arterial stiffness

Ag/mgo nanoparticles via gas aggregation nanocluster source for perovskite solar cell engineering

Nanocluster aggregation sources based on magnetron-sputtering represent precise and versatile means to deposit a controlled quantity of metal nanoparticles at selected interfaces. In this work, we exploit this methodology to produce Ag/MgO nanoparticles (NPs) and deposit them on a glass/FTO/TiO2 substrate, which constitutes the mesoscopic front electrode of a monolithic perovskite-based solar cell (PSC). Herein, the Ag NP growth through magnetron sputtering and gas aggregation, subsequently covered with MgO ultrathin layers, is fully characterized in terms of structural and morphological properties while thermal stability and endurance against air-induced oxidation are demonstrated in accordance with PSC manufacturing processes. Finally, once the NP coverage is optimized, the Ag/MgO engineered PSCs demonstrate an overall increase of 5% in terms of device power conversion efficiencies (up to 17.8%)

Highly efficient plasmon-mediated electron injection into cerium oxide from embedded silver nanoparticles

The coupling with plasmonic metal nanoparticles (NPs) represents a promising opportunity to sensitize wide band gap oxides to visible light. The processes which come into play after the excitation of localized surface plasmon resonances (LSPRs) in the NPs largely determine the efficiency of the charge/ energy transfer from the metal NP to the oxide. We report a study of plasmon-mediated energy transfer from mass-selected silver NPs into the cerium oxide matrix in which they are embedded. Femtosecond transient absorption spectroscopy is used to probe the dynamics of charge carrier relaxation after the excitation of the LSPR of the silver nanoparticles and to evaluate the plasmon-mediated electron transfer efficiency from the silver nanoparticles to the cerium oxide. High injection efficiencies in the 6-16% range have been identified for excitation between 400 and 600 nm. These high values have been explained in terms of plasmon-mediated direct electron injection as well as indirect hot electron injection from the NPs to the oxide. The information obtained provides an important contribution towards a knowledge- driven design of efficient cerium oxide based nanostructured materials for solar to chemical energy conversion

Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

Films of Ni@CoO core-shell nanoparticles (NP Ni core size d ≈ 11 nm) have been grown on Si/SiOx and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L2,3 absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film