Plasmonic properties and stability of Au and Cu nanoparticles embedded in cerium oxide.

With the aim of sensitizing cerium oxide-a very important catalytic material-to visible light, its coupling with Au and Cu nanoparticles is investigated. The samples are grown by physical synthesis by embedding a layer of nanoparticles between two cerium oxide films. The films are controlled in composition byx-ray photoemission spectroscopy and in morphology byscanning electron microscopy.

Morphology and Optical Properties of Gas-Phase-Synthesized Plasmonic Nanoparticles: Cu and Cu/MgO.

In this paper, an investigation of the properties of Cu and Cu/MgO nanoparticles (NPs) is presented. The NPs were obtained with gas-phase synthesis, and the MgO shells or matrices were formed via the co-deposition method on inert substrates. SEM and AFM were used to investigate the NP morphology on Si/SiO, quartz, and HOPG.

OBP-functionalized/hybrid superparamagnetic nanoparticles for treatment.

Infections caused by the opportunistic yeast are one of the major life threats for hospitalized and immunocompromised patients, as a result of antibiotic and long-term antifungal treatment abuse. Odorant binding proteins can be considered interesting candidates to develop systems able to reduce the proliferation and virulence of this yeast, because of their intrinsic antimicrobial properties and complexation capabilities toward farnesol, the major quorum sensing molecule of . In the present study, a hybrid system characterized by a superparamagnetic iron oxide core functionalized with bovine odorant binding protein (bOBP) was successfully developed.

Ultrafast Formation of Small Polarons and the Optical Gap in CeO.

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 CeO 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.

Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation.

We investigate the mechanism of H activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces.

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.

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.

Dynamics of the Interaction Between Ceria and Platinum During Redox Processes.

The work is focused on understanding the dynamics of the processes which occur at the interface between ceria and platinum during redox processes, by investigating an inverse catalytic model system made of ceria epitaxial islands and ultrathin films supported on Pt(111). The evolution of the morphology, structure and electronic properties is analyzed in real-time during reduction and oxidation, using low-energy electron microscopy and spatially resolved low-energy electron diffraction. The reduction is induced using different methods, namely thermal treatments in ultra-high vacuum and in H as well as deposition of Ce on the oxide surface, while re-oxidation is obtained by exposure to oxygen at elevated temperature.

Role of cerium oxide in bioactive glasses during catalytic dissociation of hydrogen peroxide.

The addition of cerium oxide to bioactive glasses, important materials for bone tissue regeneration, has been shown to induce multifunctionality, combining a significant bioactivity with antioxidant properties. We provide a real time investigation of the evolution of the electronic properties of highly diluted cerium ions in a liquid environment containing hydrogen peroxide - the most abundant reactive oxygen species in living cells. This challenging task is undertaken by means of high-energy resolution fluorescence detected by X-ray absorption near-edge spectroscopy at the Ce L3 edge.

Contraction, cation oxidation state and size effects in cerium oxide nanoparticles.

An accurate description of the structural and chemical modifications of cerium oxide nanoparticles (NPs) is mandatory for understanding their functionality in applications. In this work we investigate the relation between local atomic structure, oxidation state, defectivity and size in cerium oxide NPs with variable diameter below 10 nm, using x-ray absorption fine structure analysis in the near and extended energy range. The NPs are prepared by physical methods under controlled conditions and analyzed in morphology and crystalline quality by high resolution transmission electron microscopy.

Influence of defect distribution on the reducibility of CeO2-x nanoparticles.

Ceria nanoparticles (NPs) are fundamental in heterogeneous catalysis because of their ability to store or release oxygen depending on the ambient conditions. Their oxygen storage capacity is strictly related to the exposed planes, crystallinity, density and distribution of defects. In this work a study of ceria NPs produced with a ligand-free, physical synthesis method is presented.

Electronic properties of epitaxial cerium oxide films during controlled reduction and oxidation studied by resonant inelastic X-ray scattering.

We investigated the evolution of the electronic structure of cerium oxide ultrathin epitaxial films during reduction and oxidation processes using resonant inelastic X-ray scattering at the Ce L3 absorption edge, a technique sensitive to the electronic configurations at the 4f levels and in the 5d band thanks to its high energy resolution. We used thermal treatments in high vacuum and in oxygen partial pressure to induce a controlled and reversible degree of reduction in cerium oxide ultrathin epitaxial films of different thicknesses. Two dominant spectral components contribute to the measured spectra at the different degrees of oxidation/reduction.

Metal Adatoms and Clusters on Ultrathin Zirconia Films.

Nucleation and growth of transition metals on zirconia has been studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Since STM requires electrical conductivity, ultrathin ZrO films grown by oxidation of PtZr(0001) and PdZr(0001) were used as model systems. DFT studies were performed for single metal adatoms on supported ZrO films as well as the (1̅11) surface of monoclinic ZrO.

Tunability of exchange bias in Ni@NiO core-shell nanoparticles obtained by sequential layer deposition.

Films of magnetic Ni@NiO core-shell nanoparticles (NPs, core diameter d ≅ 12 nm, nominal shell thickness variable between 0 and 6.5 nm) obtained with sequential layer deposition were investigated, to gain insight into the relationships between shell thickness/morphology, core-shell interface, and magnetic properties. Different values of NiO shell thickness t(s) could be obtained while keeping the Ni core size fixed, at variance with conventional oxidation procedures where the oxide shell is grown at the expense of the core.

Structure, Morphology and Reducibility of Epitaxial Cerium Oxide Ultrathin Films and Nanostructures.

Cerium oxide is a very interesting material that finds applications in many different fields, such as catalysis, energy conversion, and biomedicine. An interesting approach to unravel the complexity of real systems and obtain an improved understanding of cerium oxide-based materials is represented by the study of model systems in the form of epitaxial ultrathin films or nanostructures supported on single crystalline substrates. These materials often show interesting novel properties, induced by spatial confinement and by the interaction with the supporting substrate, and their understanding requires the use of advanced experimental techniques combined with computational modeling.

Evidence of catalase mimetic activity in Ce(3+)/Ce(4+) doped bioactive glasses.

The ability of Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of hydrogen peroxide, by mimicking the catalase enzyme activity is demonstrated here for the first time. The antioxidant properties of three bioactive glasses containing an increasing amount of CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS and UV-vis measurements allowed us to determine the Ce(3+)/Ce(4+) ratio in the bulk and on the glass surface, and to correlate it with the ability of the samples to show catalase mimetic activity.

Morphology, structural properties and reducibility of size-selected CeO2- x nanoparticle films.

Non-stoichiometric ceria nanoparticles (NPs) were obtained by a gas aggregation source with a magnetron and were mass-selected with a quadrupole mass filter. By varying magnetron power, Ar gas flow, and the length of the aggregation tube, NPs with an average diameter of 6, 9, and 14 nm were synthesized and deposited onto a substrate, thus obtaining NP films. The morphology of the films was studied with scanning electron microscopy, while high resolution transmission electron microscopy was used to gain a deeper insight into the atomic structure of individual NPs.

Oxide/metal interface distance and epitaxial strain in the NiO/Ag(001) system.

Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and ab initio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3+/-0.