Highly size-controlled synthesis of Au/Pd nanoparticles by inert-gas condensation

Gold/Palladium nanoparticles were fabricated by inert-gas condensation on a sputtering reactor. With this method, by controlling both the atmosphere on the condensation chamber and the magnetron power, it was possible to produce nanoparticles with a high degree of monodispersity in size. The structure and size of the Au/Pd nanoparticles were determined by mass spectroscopy, and confirmed by atomic force microscopy and electron transmission microscopy measurements. The chemical composition was analyzed by X-ray microanalysis. From these measurements we confirmed that with the sputtering technique we are able to produce particles of 1, 3, and 5 nm on size, depending on the choice of the synthesis conditions. From TEM measurements made both in the regular HREM, as well as in STEM-HAADF mode, we found that the particles are icosahedral in shape, and the micrographs show no evidence of a core-shell structure, in contrast to what is observed in the case of nanoparticles prepared by chemical synthesis

Gold–palladium core@shell nanoalloys: experiments and simulations

In this work, we report a facile synthesis route, structural characterization, and full atomistic simulations of gold–palladium nanoalloys. Through aberration corrected-STEM, UV-vis spectroscopy and EDS chemical analysis, we were able to determine that Au(core)–Pd(shell) bimetallic nanoparticles were formed. Using different computational approaches, we were capable of establishing how the size of the core and the thickness of the shell will affect the thermodynamic stability of several core–shell nanoalloys. Finally, grand canonical simulations using different sampling procedures were used to study the growth mechanism of Pd atoms on Au seeds of different shapes

Metal-Semiconductor Interfaces in Thin-Film Transistors

The metal-semiconductor interface in thin-film transistors (TFTs) is one of the bottlenecks on the development of these devices. Although this interface does not play an active role in the transistor operation, a low-quality interface can be responsible for a low performance operation. In a-Si TFTs, a doped film can be used to improve this interface, however, in other TFT technologies, there is no doped film to be used. In this chapter, some alternatives to improve this interface are analysed. Also, the influence of this interface on the electrical stability of these devices is presented

Influence of morphology in the catalytic activity of bioconjugated platinum nanostructures

Abstract: Platinum nanoparticles stabilized by a protein, bovine serum albumin, have been synthesized successfully with two different morphologies such as cuboctahedra and nanorods. They have been characterized by the use of different techniques such as XPS, PCS, TEM, and STEM-HAADF. These nanoparticles have been applied as catalysts for the hydrogenation of allyl alcohol in an aqueous solution. A key finding of this article is the superior catalytic activity of the nanorods compared to the cuboctahedral particles. This difference in the catalytic activity was justified because of the variation in the amount of protein to stabilize the nanorods. A model for the nanorods and equations that describe the proportion of atoms in the different sites of the particle (face, vertex, edge, or interior) is used to calculate the percentage of atoms that are located on the nanorod surface. The stability of these particles as catalysts was also studied. The results showed that Pt nanorods and Pt cuboctahedra particles were degraded after 24 h of reactio

Insights into the capping and structure of MoS2 nanotubes as revealed by aberration-corrected STEM

Aberration-corrected electron microscopy (STEM-HAADF) has been used for the first time to understand the capping, nature and structure of the MoS2 nanotubes. The MoS2 nanotubes that have been obtained have various unusual faceted caps presumably arising from the presence of topological defects. A detailed study of the capping of the nanotubes, along with identification that the MoS2 nanotubes are of the zigzag type have been carried out using both experimental and simulated STEM images. The presence of 3R-rhombohedral stacking of the MoS2 nanotubes has been identified

On the structure of Au/Pd bimetallic nanoparticles

We performed a study on bimetallic Au/Pd nanoparticles using aberration corrected electron microscopy along with molecular dynamics simulations to investigate the features of specific atomic sites at the surface, which can be related to the high catalytic activity properties of the particles. The calculations mimic the growth of nanoparticles through a cooling process from a molten solid to a crystalline structure at room temperature. We found that the final structure for the alloy particles is neither a cuboctahedral nor an icosahedral,but a complex structure that has a very rough surface and unique isolated Pd sites surrounded by Au atoms. We also found that there is predominance of three specific Pd sites at the surface, which can be directly related to the catalytic activity of the nanoparticle

Left ventricular filling patterns in patients with previous myocardial infarction measured by conventional cine cardiac magnetic resonance

To explore left ventricular filling patterns in patients with a history of previous myocardial infarction (MI) using time-volume curves obtained from conventional cine-cardiac magnetic resonance (CMR) examinations. Consecutive patients with a history of previous MI who were referred for CMR evaluation constituted the study population, and a consecutive cohort of sex and age-matched patients with a normal CMR constituted the control group. The following CMR diastolic parameters were evaluated: peak filling rate (PFR), time to PFR (tPFR), normalised PFR adjusted for diastolic volume at PFR (nPFR), and percent RR interval between end systole and PFR. Fifty patients were included, 25 with a history of previous MI and 25 control. The mean age was 59.6 ± 13.9 years and 27 (54%) were male. Within the control group, age was significantly related to PFR (r = -0.53, p = 0.007), whereas among patients with previous MI age was not related to PFR (r = -0.16, p = 0.44). PFR (252.4 ± 96.7 ml/s vs. 316.0 ± 126.4 ml/s, p = 0.05) and nPFR (1.6 ± 1.2 vs. 3.3 ± 1.5, p<0.001) were significantly lower in patients with previous MI, whereas no significant differences were detected regarding tPFR (143.0 ± 67.5 ms vs. 176.2 ± 83.9 ms, p = 0.13) and % RR to PFR (18.1 ± 9.7% vs. 20.6 ± 12.2%, p = 0.44). MI size was related to LV ejection fraction (r = -0.76, p<0.001), PFR (r = -0.40, p = 0.004), nPFR (r = -0.52, p<0.001) and left atrium area (r = 0.40, p = 0.004). Patients at the lowest PFR quartile (<200 ml/s) showed a larger MI size (Q1 26.5 ± 25.5%, Q2 15.5 ± 20.9%, Q3 6.3 ± 12.4%, Q4 8.8 ± 14.1%, p = 0.04). At multivariate analysis, MI size was the only independent predictor of the lowestPFR (p = 0.017). Infarct size has an impact on LV filling profiles, as assessed by conventional cine CMR without additional specific pulse sequences.Fil: Rodriguez Granillo, Gaston Alfredo. Sanatorio "Otamendi y Miroli S.A.". Servicio de Diagnóstico por Imágenes. Departamento de Imágenes en Cardiología. Centro de Investigaciones Cardiovasculares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mejía Campillo, Marlon. No especifíca;Fil: Rosales, Miguel A.. Sanatorio "Otamendi y Miroli S.A.". Servicio de Diagnóstico por Imágenes. Departamento de Imágenes en Cardiología. Centro de Investigaciones Cardiovasculares; ArgentinaFil: Bolzán, Gabriel. No especifíca;Fil: Ingino, Carlos. No especifíca;Fil: López, Federico. No especifíca;Fil: Degrossi, Elina. Sanatorio "Otamendi y Miroli S. A."; ArgentinaFil: Lylyk, Pedro. Sanatorio "Otamendi y Miroli S. A."; Argentin