Search results for "clusters"

IONIC TRANSPORT ACROSS POROUS CHARGED MEMBRANES AND THE GOLDMAN CONSTANT FIELD ASSUMPTION

1986

Starting from a simple theoretical model based on Nernst-Planck flux equations and the Donnan equilibrium relationship, the ionic transport across a porous, charged membrane is analysed and conditions are given which make exact the so-called “constant field assumption”. The validity of the reported results is later verified in the case of a well-known problem: the ionic transport across a cation-exchange membrane under bi-ionic conditions.

Semiempirical pseudopotential approach for nitride-based nanostructures and {\it ab initio} based passivation of free surfaces

2013

We present a semiempirical pseudopotential method based on screened atomic pseudopotentials and derived from \textit{ab initio} calculations. This approach is motivated by the demand for pseudopotentials able to address nanostructures, where \textit{ab initio} methods are both too costly and insufficiently accurate at the level of the local-density approximation, while mesoscopic effective-mass approaches are inapplicable due to the small size of the structures along, at least, one dimension. In this work we improve the traditional pseudopotential method by a two-step process: First, we invert a set of self-consistently determined screened {\it ab initio} potentials in wurtzite GaN for a ra…

Protected Metallic Clusters, Quantum Wells and Metal-Nanocrystal Molecules

2010

Electronic Structure

2015

Abstract This chapter discusses the origin of fermionic shell structure in confined quantum systems, its application to metal clusters and clusters that are stabilized by an organic ligand layer (the so-called monolayer-protected clusters, MPCs). It reviews briefly the so-called superatom concept which has become central in the MPC field in recent years. It also contains a rather extensive table listing most of the structurally known MPCs, where the metal core is of gold, silver, copper, aluminum, or other main-group elements.

Comparative Genomics Analysis of Keratin-Degrading Chryseobacterium Species Reveals Their Keratinolytic Potential for Secondary Metabolite Production

2021

A promising keratin-degrading strain from the genus Chryseobacterium (Chryseobacterium sp. KMC2) was investigated using comparative genomic tools against three publicly available reference genomes to reveal the keratinolytic potential for biosynthesis of valuable secondary metabolites. Genomic features and metabolic potential of four species were compared, showing genomic differences but similar functional categories. Eleven different secondary metabolite gene clusters of interest were mined from the four genomes successfully, including five common ones shared across all genomes. Among the common metabolites, we identified gene clusters involved in biosynthesis of flexirubin-type pigment, m…

Ellipsoid-shaped superparamagnetic nanoclusters through emulsion electrospinning.

2015

Ellipsoid-shaped nanoclusters composed of single superparamagnetic nanoparticles can be generated by emulsion electrospinning. Stretching and subsequent solvent evaporation of iron oxide loaded emulsion droplets during the emulsion electrospinning process enables the creation of such structures embedded in polymer nanofibers. Dissolution of the polymer fibers yields an aqueous dispersion of the inorganic clusters which are the first example of ellipsoid-shaped superparamagnetic nanoclusters with a high saturation magnetization (∼47 emu g(-1)).

Time resolved photofragmentation of Au $_{n}^{+}$ and Ag $_{n}^{+}$ clusters (n = 9, 21)

1997

Gold and silver cluster ions were produced by laser vaporization and stored in a Penning trap. After mass selection the cluster sizes of interest were illuminated by a laser pulse and electronically excited. Photoabsorption cross sections and fragmentation patterns were measured for photon energies of 2.3 eV to 5.2 eV. Unimolecular dissociation was observed time resolved on a microsecond to millisecond scale. Dissociation energies were deduced from the measured life times.

The gold-sulfur interface at the nanoscale.

2012

Thiolate-protected gold surfaces and interfaces, relevant for self-assembled monolayers of organic molecules on gold, for passivated gold nanoclusters and for molecule-gold junctions, are archetypal systems in various fields of current nanoscience research, materials science, inorganic chemistry and surface science. Understanding this interface at the nanometre scale is essential for a wide range of potential applications for site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, functionalization of gold surfaces for sensing, molecular recognition and molecular electronics, and gold nanoparticle catalysis. During the past five years, considerable experimental …

Surface plasmons and vibrations of self-assembled silver nanocolumns

2006

6 pags. ; 5 figs. 1 tab.

On novel magnetic probe for fullerene characterization: Theoretical studies on NMR parameters of free and confined in fullerenes HD and H2 molecules

2015

Chemical characterization and separation of individual fullerenes from a raw reaction mixture need new and efficient tools, including rapid spectroscopic techniques. Recent "molecular surgery" synthesis of endohedral complexes of fullerenes with selected atoms and small molecules has opened a new path for experimental and theoretical studies on structural and spectroscopic properties of these molecular systems. Among them are fullerenes with molecular hydrogen confined within a nanoscale cavity. In this work we report on quantum-chemical prediction of nuclear magnetic shielding (and chemical shift) and indirect spin-spin coupling constant in free HD and H2 molecules, as well as models of co…