Influence of size, shape and core-shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiOx

This is an Open Access article under the terms of the Creative Commons Attribution License.-- et al.Ag and Ag@MgO core-shell nanoparticles (NPs) with a diameter of d = 3-10 nm were obtained by physical synthesis methods and deposited on Si with its native ultrathin oxide layer SiOx (Si/SiOx). Scanning electron microscopy and transmission electron microscopy (TEM) images of bare Ag NPs revealed the presence of small NP aggregates caused by diffusion on the surface and agglomeration. Atomic resolution TEM gave evidence of the presence of crystalline multidomains in the NPs, which were due to aggregation and multitwinning occurring during NP growth in the nanocluster source. Co-deposition of Ag NPs and Mg atoms in an oxygen atmosphere gave rise to formation of a MgO shell matrix surrounding the Ag NPs. The behaviour of the surface plasmon resonance (SPR) excitation in surface differential reflectivity (SDR) spectra with p-polarised light was investigated for bare Ag and Ag@MgO NPs. It was shown that the presence of MgO around the Ag NPs caused a red shift of the plasmon excitation, and served to preserve its existence after prolonged (five months) exposure to air, realizing the possibility of technological applications in plasmonic devices. The Ag NP and Ag@MgO NP film features in the SDR spectra could be reproduced by classical electrodynamics simulations by treating the NP-containing layer as an effective Maxwell Garnett medium. The simulations gave results in agreement with the experiments when accounting for the experimentally observed aggregation.This work has been supported by the Italian MIUR under grant FIRB RBAP115AYN (Oxides at the nanoscale: multifunctionality and applications).Peer Reviewe

Reducible oxides as ultrathin epitaxial films

This chapter reviews and discusses recent work on two-dimensional films of reducible oxides supported on metal substrates. In general, peculiar chemical and structural phases, different from the bulk ones, can be stabilized depending on the oxygen chemical potential, on kinetic processes and on the specific substrate used. A peculiarity of reducible oxides is that the observed phases can often be reversibly transformed one into the other by applying reducing and oxidizing treatments

Scanning tunneling microscopy and photoemission studies of self-organised Ag nanostructures on the N-modified Cu(001) surface

There has been a strong interest in methods of creating nanometer scale structures and in particular forming one and two-dimensional electron confinement structures. Self -organisation has been recognised as a promising way for growing large nanostructure domains with sufficiently regular size and spacing as required for the observation of quantum well states. We investigated the electronic properties and the morphology of Ag nano structures on c(2 x 2)-N/Cu(001) surface. This system is an example of epitaxial growth confined on nanoscale regions due to the occurrence of an adsorbate induced reconstruction. Using a combination of Scanning Tunneling Microscopy and Angle Resolved Photoemission Spectroscopy techniques we were able to determine the morphology and the growth mode of Ag on N -modified Cu(001) surface and the occurrence of quantum size effects in the electron properties of Ag nanostripes and nanoislands, evidenced in the observation of quantum well states

A brief tutorial for the STEM-CELL software

TEM and STEM analytical studies are going in toward a stronger involvement of computing for the image interpretation. Geometric Phase Analysis [1], for example, has proved to be a useful tool to evaluate the strain in different structures. TEM Image simulations are another very important tool to be compared with complicated structures to obtain quantitative interpretation of the contrast

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. The NP films were grown by a magnetron sputtering based gas aggregation source and studied by high resolution- and scanning-transmission electron microscopy and x-ray photoelectron spectroscopy. In particular, the influence of the oxidation procedure on the NP reducibility has been investigated. The different reducibility has been correlated to the exposed planes, crystallinity and density and distribution of structural defects. The results obtained in this work represent a basis to obtain cerium oxide NP with desired oxygen transport properties

Could internal jugular vein ultrasound be useful in the assessment of patients with heart failure? A systematic review

Many recent studies have validated the internal jugular vein ultrasound (IJV-US) for estimating volemic status in critical patients. If research confirms its accuracy in detecting intravascular volume, congestion, and prognosis, this method could help manage heart failure (HF) because it is simple, fast, and applicable in several settings. This review examines the IJV-US’s reliability, diagnostic accuracy, and ability to predict poor outcomes for HF, as well as its correlation with surrogate congestion tests like natriuretic peptides and elevated central venous pressure (CVP). Our systematic review followed the PRISMA statement for systematic reviews and meta-analyses. Eleven studies examined the reliability and validity of IJV-US measures in predicting congestion, volume status, and prognosis in adult spontaneously breathing HF patients. We searched PubMed, Cochrane Library, and EMBASE. IJV-US measurements using Valsalva and sniffing seem more accurate for predicting congestion, volume status, high CVP, and poor prognosis. The IJV ratio in chronic HF and out-hospital patients and the absence of IJV area [cross-sectional area (CSA)] changes in acute HF (AHF) and in-hospital patients are the most validated measurements. No evidence suggests the method is reliable between and within raters. AHF patients’ IJV ratio and CSA absence appear to correlate with CVP and atrial natriuretic peptides. In conclusion, the IJV-US may be useful for managing HF patients, but more research is needed to confirm its reliability and prognostic accuracy. Develop a standard US protocol lastly

Circulating Levels of Proprotein Convertase Subtilisin/Kexin Type 9 and Arterial Stiffness in a Large Population Sample: Data From the Brisighella Heart Study

Proprotein convertase subtilisin/kexin type 9 (PCSK9) circulating levels are significantly associated with an increased risk of cardiovascular events. This study aimed to evaluate the relationship between circulating levels of PCSK9 and arterial stiffness, an early instrumental biomarker of cardiovascular disease risk, in a large sample of overall healthy participants

Influence of size, shape and core\u2013shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiOx

Ag and Ag@MgO core-shell nanoparticles (NPs) with a diameter of d = 3-10 nm were obtained by physical synthesis methods and deposited on Si with its native ultrathin oxide layer SiOx (Si/SiOx). Scanning electron microscopy and transmission electron microscopy (TEM) images of bare Ag NPs revealed the presence of small NP aggregates caused by diffusion on the surface and agglomeration. Atomic resolution TEM gave evidence of the presence of crystalline multidomains in the NPs, which were due to aggregation and multitwinning occurring during NP growth in the nanocluster source. Co-deposition of Ag NPs and Mg atoms in an oxygen atmosphere gave rise to formation of a MgO shell matrix surrounding the Ag NPs. The behaviour of the surface plasmon resonance (SPR) excitation in surface differential reflectivity (SDR) spectra with p-polarised light was investigated for bare Ag and Ag@MgO NPs. It was shown that the presence of MgO around the Ag NPs caused a red shift of the plasmon excitation, and served preserve its existence after prolonged (five months) exposure to air, realizing the possibility of technological applications in plasmonic devices. The Ag NP and Ag@MgO NP film features in the SDR spectra could be reproduced by classical electrodynamics simulations by treating the NP-containing layer as an effective Maxwell Garnett medium. The simulations gave results in agreement with the experiments when accounting for the experimentally observed aggregation

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 L-3 edge. We investigate samples with variable compositions and different morphologies. We relate the observed spectroscopic changes not only to variations in the concentration of the two Ce oxidation states in the samples, but also to changes in the local atomic environment of Ce ions, providing a clear picture of the role of cerium ions in the dissociation of hydrogen peroxide. The obtained results contribute to the understanding of the mechanisms that come into play in the process and provide a basis for the optimization of the functionalities of this class of materials