Variation of the Core Atomic Structure of Thiolated (Au_<i>x</i>Ag_1–<i>x</i>)_312±55 Nanoclusters with Composition from Aberration-Corrected HAADF STEM

We have investigated the atomic structure of thiol-protected (Au_<i>x</i>Ag_1–<i>x</i>)_312±55 clusters as a function of composition (<i>x</i>) by using aberration-corrected Scanning Transmission Electron Microscopy (STEM), in High Angle Annular Dark Field (HAADF) mode, combined with multislice electron scattering simulations of the STEM images. Three structural motifs are considered: icosahedral, fcc, and ino-decahedral. A combination of STEM intensity and diameter measurement is used to “fractionate” the deposited sample according to composition for atomic resolution imaging. We find that the structure depends critically on composition: the icosahedral structure dominates in Ag-rich clusters, while the fcc structure dominates in Au-rich clusters. The ino-decahedral structure was only observed in clusters with Au content greater than 30%

A High Resolution Study of Dynamic Changes of Ce₂O₃ and CeO₂ Nanoparticles in Complex Environmental Media

Ceria nanoparticles (NPs) rapidly and easily cycle between Ce­(III) and Ce­(IV) oxidation states, making them prime candidates for commercial and other applications. Increased commercial use has resulted in increased discharge to the environment and increased associated risk. Once in complex media such as environmental waters or toxicology exposure media, the same redox transformations can occur, causing altered behavior and effects compared to the pristine NPs. This study used high resolution scanning transmission electron microscopy and electron energy loss spectroscopy to investigate changes in structure and oxidation state of small, polymer-coated ceria suspensions in complex media. NPs initially in either the III or IV oxidation states, but otherwise identical, were used. Ce­(IV) NPs were changed to mixed (III, IV) NPs at high ionic strengths, while the presence of natural organic macromolecules (NOM) stabilized the oxidation state and increased crystallinity. The Ce­(III) NPs remained as Ce­(III) at high ionic strengths, but were modified by the presence of NOM, causing reduced crystallinity and degradation of the NPs. Subtle changes to NP properties upon addition to environmental or ecotoxicology media suggest that there may be small but important effects on fate and effects of NPs compared to their pristine form

Social aspects of Spanish post-war literature: The Hive and The Story of a Stairway.

This bachelor's thesis examines social aspects of Spanish post-war literature. It focuses on two works of first period of Francoism, on novel The Hive, written by Camilo José Cela and on drama The Story of a Stairway, written by Antonio Buero Vallejo. In the theoretical part, the thesis describes indispensable historic and socioeconomic context, Spanish Civil War, and subsequent post-war period with focus on immediate consequences, the regime itself, the economics and society. Thereafter it briefly describes the literature of post-war period, and the life of both authors. In the second, more practical part, the thesis concentrates on particular social aspects which can be found in the literary works, and the works are compared within the themes. The themes are everyday life, poverty and hunger, prostitution, advancement on the social ladder and hope. Key words Camilo José Cela, Antonio Buero Vallejo, post-war literature, Spanish civil war, social aspects, lower class of societ

Synthesis of FITC alginate.

<p>(Ai) Reaction coupling scheme of FITC onto alginate under peptide coupling conditions. (Aii) Image of fluorescent alginate in normal light (left) and exposed to λ = 365 nm UV light (right). (B) Absorption and emission (red and blue lines respectively) spectra of the fluorescent alginate (FlAlg) product. The native alginate reactant has no absorption or emission profile, however, upon conjugation with FITC a highly absorption and emission peaks are observed.</p

Effects of alginate on cellular iron transport.

<p>(A) Intracellular iron concentration decreases when RKO cells were incubated with iron-59 and alginate (0.3% w/v) compared to iron only control (B) Treatment of RKO cells with iron increases ferritin expression whilst co-incubation with alginate (0.3% w/v) significantly suppressed the iron mediated ferritin induction. All experiments were performed in triplicate with error bars representing +/- SEM and * denotes statistical significance at p < 0.05.</p

Site-Specific Assembly of Fullerene Nanorings Guided by Two-Dimensional Gold Clusters

Molecules can self-assemble rather easily into straight one-dimensional wires via covalent or noncovalent bonding. To organize molecules into cyclic structures such as rings or loops where the number of molecules forming each structure is accurately controlled is a much more challenging task. Here we demonstrate the construction of fullerene nanorings on the (111) plane of gold using single-atomic-layer-high gold islands as the seeding agent. C₆₀ molecules are trapped by the step edges of the seeding Au island leading to the formation of molecular rings. The smallest ring consists of six C₆₀ molecules encircling 19 Au atoms. Scanning tunneling microscopy imaging reveals that the rings are formed at specific locations on the reconstructed Au(111) surface with the diameter of the ring controlled by the size of the gold island. Molecular mechanics modeling provides a detailed understanding of the relationship between the number of molecules in the ring and the number of gold atoms within the Au island

Cellular localisation of alginate with confocal microscopy.

<p>Cells were treated with iron alone (control) or iron and FITC alginate with or without cell-membrane permeabilisation. (A) Cells treated with iron alone as expected showed no FITC signal. (B) Cells treated with iron and FITC alginate showed negligible punctate FITC staining on the cell periphery (C) Cells permeabilised with Saponin and then cultured with iron and FITC alginate showed an abundance of intracellular FITC signal which was mostly cytoplasmic in localisation.</p

Au₄₀(SR)₂₄ Cluster as a Chiral Dimer of 8‑Electron Superatoms: Structure and Optical Properties

We predict and analyze density-functional theory (DFT)-based structures for the recently isolated Au₄₀(SR)₂₄ cluster. Combining structural information extracted from ligand-exchange reactions, circular dichroism and transmission electron microscopy leads us to propose two families of low-energy structures that have a chiral Au–S framework on the surface. These families have a common geometrical motif where a nonchiral Au₂₆ bi-icosahedral cluster core is protected by 6 RS–Au–SR and 4 RS–Au–SR–Au–SR oligomeric units, analogously to the “Divide and Protect” motif of known clusters Au₂₅(SR)₁₈^–/0, Au₃₈(SR)₂₄ and Au₁₀₂(SR)₄₄. The strongly prolate shape of the proposed Au₂₆ core is supported by transmission electron microscopy. Density-of-state-analysis shows that the electronic structure of Au₄₀(SR)₂₄ can be interpreted in terms of a dimer of two 8-electron superatoms, where the 8 shell electrons are localized at the two icosahedral halves of the metal core. The calculated optical and chiroptical characteristics of the optimal chiral structure are in a fair agreement with the reported data for Au₄₀(SR)₂₄

High-selectivity palladium catalysts for the partial hydrogenation of alkynes by gas-phase cluster deposition onto oxide powders

<p>The selective hydrogenation of alkynes is an important reaction in the synthesis of fine and bulk chemicals. We show that the synthesis of metal nanoparticles in the gas phase, followed by deposition onto conventional support powders results in materials that perform as well as those made by typical methods for making catalysts (impregnation, deposition). The nature of the active sites in these catalysts is explored.</p

Physical characterisation of alginate iron composites.

<p>(Ai) Low magnification STEM images of alginate-iron composites revealed the alginate network ‘decorated’ in iron (denoted by arrows) with a single highly dense iron nucleation site (denoted with an asterisk). (Aii) A higher magnification image of the nucleation centre revealed nanoparticles of approximately 2–5 nm in diameter. (B) Fast Fourier transform analysis of HAADF-STEM images of two individual nanoparticles. (C) EDX mapping of iron-alginate composites with oxygen, iron and sodium localisation shown in the sample area. The copper from the copper TEM grid functions as a control.</p