Gold cluster
Encyclopedia
Gold clusters in cluster chemistry
are gold-derived materials that can either be discrete molecules or larger colloid
al particles. Both types are describes as nanoparticles, with diameters of less than one micrometer.
s on their exteriors. Two examples are [Au6C
P(C6H5)3)
6]2+ and [Au9(P(C6H5)3)8]3+.
. Such colloids often occur with a surface coating of alkanethiols or protein
s. Such clusters can be used in immunohistochemical staining. Gold metal
nanoparticles (NPs) are characterized by an intense absorption in the visible
region, which enhances the utility of these species for the development of completely optical devices. The wavelength of this surface plasmon resonance
(SPR) band depends on the size and shape of the nanoparticles as well as their interactions with the surrounding medium. The presence of this band enhances the utility of gold nanoparticle as building blocks for devices for data storage, ultrafast switching, and gas sensors.
s are observed in the gas-phase after they have been generated by laser vaporization and can be observed in the gas phase by photoelectron spectroscopy
. Using similar gas-phase techniques that rely on mass spectrometry, the structures of neutral gold clusters have been investigated and the unique tetrahedral structure of Au20 has been confirmed.
Cluster chemistry
In chemistry, a cluster is an ensemble of bound atoms intermediate in size between a molecule and a bulk solid. Clusters exist of diverse stoichiometries and nuclearities. For example, carbon and boron atoms form fullerene and borane clusters, respectively. Transition metals and main group...
are gold-derived materials that can either be discrete molecules or larger colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
al particles. Both types are describes as nanoparticles, with diameters of less than one micrometer.
Discrete gold clusters
Well-defined, molecular clusters are known, invariably containing organic ligandLigand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s on their exteriors. Two examples are [Au6C
Carbide
In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides...
P(C6H5)3)
Triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
6]2+ and [Au9(P(C6H5)3)8]3+.
Colloidal clusters
Gold clusters can be obtained in colloid formColloidal gold
Colloidal gold is a suspension of sub-micrometre-sized particles of gold in a fluid — usually water. The liquid is usually either an intense red colour , or a dirty yellowish colour ....
. Such colloids often occur with a surface coating of alkanethiols or protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s. Such clusters can be used in immunohistochemical staining. Gold metal
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
nanoparticles (NPs) are characterized by an intense absorption in the visible
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
region, which enhances the utility of these species for the development of completely optical devices. The wavelength of this surface plasmon resonance
Surface plasmon resonance
The excitation of surface plasmons by light is denoted as a surface plasmon resonance for planar surfaces or localized surface plasmon resonance for nanometer-sized metallic structures....
(SPR) band depends on the size and shape of the nanoparticles as well as their interactions with the surrounding medium. The presence of this band enhances the utility of gold nanoparticle as building blocks for devices for data storage, ultrafast switching, and gas sensors.
Gas-phase clusters
Evidence has been presented for the existence of hollow golden cages with the partial formula Aun- with n = 16 to 18. These cluster compounds with diameter of 550 picometrePicometre
A picometre is a unit of length in the metric system, equal to one trillionth, i.e. of a metre, which is the current SI base unit of length...
s are observed in the gas-phase after they have been generated by laser vaporization and can be observed in the gas phase by photoelectron spectroscopy
X-ray photoelectron spectroscopy
X-ray photoelectron spectroscopy is a quantitative spectroscopic technique that measures the elemental composition, empirical formula, chemical state and electronic state of the elements that exist within a material...
. Using similar gas-phase techniques that rely on mass spectrometry, the structures of neutral gold clusters have been investigated and the unique tetrahedral structure of Au20 has been confirmed.
External links
- Carbon fullerenes now have metallic cousins, 'hollow golden cages' Article at physorg.com