Visualizing screening in noble-metal clusters: static dynamic.

The localized surface-plasmon resonance of metal nanoparticles and clusters corresponds to a collective charge oscillation of the quasi-free metal electrons. The polarization of the more localized d electrons opposes the overall polarization of the electron cloud and thus screens the surface plasmon. By contrast, a static electric external field is well screened, as even very small noble-metal clusters are highly metallic: the field inside is practically zero except for the effect of the Friedel-oscillation-like modulations which lead to small values of the polarization of the d electrons.

Crucial Role of Conjugation in Monolayer-Protected Metal Clusters with Aromatic Ligands: Insights from the Archetypal AuL Cluster Compounds.

Ligand-protected metal clusters are employed in a great many applications that include notably energy conversion and biomedical uses. The interaction between the ligands and the metallic cores, mediated by an often complex interface, profoundly influences the properties of small clusters, in particular. Nonetheless, the mechanisms of interaction remain far from fully understood.

Chiral-Icosahedral ( I) Symmetry in Ubiquitous Metallic Cluster Compounds (145A,60X): Structure and Bonding Principles.

There exists a special kind of perfection-in symmetry, simplicity, and stability-attainable for structures generated from precisely 60 ligands (all of a single type) that protect 145 metal-atom sites. The symmetry in question is icosahedral ( I), generally, and chiral icosahedral ( I) in particular. A 60-fold equivalence of the ligands is the smallest number to allow this kind of perfection.

Identifying Electronic Modes by Fourier Transform from δ-Kick Time-Evolution TDDFT Calculations.

Time-dependent density-functional theory (TDDFT) is widely used for calculating electron excitations in clusters and large molecules. For optical excitations, TDDFT is customarily applied in two distinct approaches: transition-based linear-response TDDFT (LR-TDDFT) and the real-time formalism (RT-TDDFT). The former directly provides the energies and transition densities of the excitations, but it requires the calculation of a large number of empty electron states, which makes it cumbersome for large systems.

Tetrahedral () Closed-Shell Cluster of 29 Silver Atoms & 12 Lipoate Ligands, [Ag(R-α-LA)]: Antibacterial and Antifungal Activity.

Here we report on the identification and applications of an aqueous 29-atom silver cluster stabilized with 12 lipoate ligands, i.e. Ag(R-α-LA) or (29,12), wherein R-α-LA = R-α-lipoic acid, a natural dithiolate.

Is the largest aqueous gold cluster a superatom complex? Electronic structure & optical response of the structurally determined Au(p-MBA).

The new water-soluble gold cluster Au(p-MBA), the structure of which has been recently determined at sub-atomic resolution by Vergara et al., is the largest aqueous gold cluster ever structurally determined and likewise the smallest cluster with a stacking fault. The core presents a twinned truncated octahedron, while additional peripheral gold atoms follow a C rotational symmetry.

MicroED Structure of Au(p-MBA) at Subatomic Resolution Reveals a Twinned FCC Cluster.

Solving the atomic structure of metallic clusters is fundamental to understanding their optical, electronic, and chemical properties. Herein we present the structure of the largest aqueous gold cluster, Au(p-MBA) (p-MBA: para-mercaptobenzoic acid), solved by electron micro-diffraction (MicroED) to subatomic resolution (0.85 Å) and by X-ray diffraction at atomic resolution (1.

Surface plasmons in quantum-sized noble-metal clusters: TDDFT quantum calculations and the classical picture of charge oscillations.

The localized surface-plasmon resonance of metal nanoparticles corresponds to a classical charge oscillation of the quasi-free conduction electrons. In the case of noble-metal nanoparticles, interband transitions from the d electrons influence the spectra strongly. In addition, the inhomogeneity of the nanoparticles at the atomistic level becomes important for small sizes.

Optical response of quantum-sized Ag and Au clusters--cage vs. compact structures and the remarkable insensitivity to compression.

Quantum-sized silver and gold clusters show very different spectral characteristics. While silver exhibits a strong localized surface-plasmon resonance (LSPR) band down to very small sizes, the resonance is broadened beyond recognition in Au clusters below about 2 nm. In the present work, we study icosahedral hollow-shell structures, or cages, of about 1.

Aspect-ratio- and size-dependent emergence of the surface-plasmon resonance in gold nanorods--an ab initio TDDFT study.

It is known that the surface-plasmon resonance (SPR) in small spherical Au nanoparticles of about 2 nm is strongly damped. We demonstrate that small Au nanorods with a high aspect ratio develop a strong longitudinal SPR, with intensity comparable to that in Ag rods, as soon as the resonance energy drops below the onset of the interband transitions due to the geometry. We present ab initio calculations of time-dependent density-functional theory of rods with lengths of up to 7 nm.

Atomic and electronic properties of quasi-one-dimensional MOS nanowires.

The structural, electronic and magnetic properties of quasi-one-dimensional MoS nanowires, passivated by extra sulfur, have been determined using density-functional theory. The nanostructures were simulated using several different models based on experimental electron microscopy images. It is found that independently of the geometrical details and the coverage of extra sulfur at the Mo-edge, quasi-one-dimensional metallic states are predominant in all the low-energy model structures despite their reduced dimensionality.

Enantiospecific adsorption of chiral molecules on chiral gold clusters.

Enantioselectivity in gold clusters is investigated by studying the adsorption of a chiral amino acid (cysteine) on a chiral Au55 cluster using density functional calculations. The highest adsorption energies were found when the amino and thiolate functional groups of cysteine are bonded to the lowest coordinated edges of the chiral cluster. Enantiospecific adsorption is primarily obtained from the different bond location and strength, at the cluster edge, of the carboxyl groups forming the left- and right-handed enantiomers.