Gold clusters ranging in diameter from 1 to 6 nanometers have been prepared on single crystalline surfaces of titania in ultrahigh vacuum to investigate the unusual size dependence of the low-temperature catalytic oxidation of carbon monoxide. Scanning tunneling microscopy/spectroscopy (STM/STS) and elevated pressure reaction kinetics measurements show that the structure sensitivity of this reaction on gold clusters supported on titania is related to a quantum size effect with respect to the thickness of the gold islands; islands with two layers of gold are most effective for catalyzing the oxidation of carbon monoxide. These results suggest that supported clusters, in general, may have unusual catalytic properties as one dimension of the cluster becomes smaller than three atomic spacings.

Onset of Catalytic Activity of Gold Clusters on Titania with the Appearance of Nonmetallic Properties

Size- and support-dependency in the catalysis of gold

The Conservation of Orbital Symmetry

Perylene bisimide dyes as versatile building blocks for functional supramolecular architectures

Highly fluorescent, water-soluble, few-atom noble-metal quantum dots have been created that behave as multielectron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near infrared. These molecular metals exhibit highly polarizable transitions and scale in size according to the simple relation EFermi/N1/3, predicted by the free-electron model of metallic behavior. This simple scaling indicates that fluorescence arises from intraband transitions of free electrons, and these conduction-electron transitions are the low-number limit of the plasmon—the collective dipole oscillations occurring when a continuous density of states is reached. Providing the missing link between atomic and nanoparticle behavior in noble metals, these emissive, water-soluble Au nanoclusters open new opportunities for biological labels, energy-transfer pairs, and light-emitting sources in nanoscale optoelectronics.

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Highly fluorescent noble-metal quantum dots.

Stereospecific Conversion of cis-trans Isomeric Aziridines to Open-Chain Azomethine Ylides

Aus Propiolsaure-methylester und prim. Aminen entstehen cis- und trans-3-Amino-acrylsauremethylester; im Gleichgewicht bevorzugt ist das cis-Isomere mit intramolekularer H-Brucke. Bei den Addukten der sek. Amine ist die trans-Konfiguration die thermodynamisch stabile. Auch aus den Amin-Additionen an Acetylendicarbonsaure-dimethylester gehen cis-trans-Gemische hervor; die stabilen Addukte primarer Amine gehoren der Amino-fumarsaureester-Reihe, die von sek. Aminen der Amino-maleinsaureester-Reihe an. Die Konfigurationszuweisungen grunden sich auf NMR-, IR-, UV-Spektren und Dipolmomente.

Die Addukte primärer und sekundärer Amine an Carbonester der Acetylenreihe und ihre Konfiguration

Cryophotoclustering techniques for synthesizing very small, naked silver clusters Agn of known size (where n = 2-5). The molecular metal cluster-bulk metal particle interface

Die chemischen Verschiebungen der Ringprotonen von 36 substituierten 1.3-Diphenyl-Δ2-pyrazolinen und von 23 substituierten 3-Phenyl-Δ2-isoxazolinen werden mit denen der Stammkorper verglichen. Die Methode der kleinsten Fehlerquadrate fuhrt zu den Parametern Δτ fur gem., cis-vic. und trans-vic. Substituenten. Diese Substituenteneffekte werden theoretisch diskutiert und sind von diagnostischem Wert bei der Strukturermittlung.

1.3-Dipolare Cycloadditionen, XXX. Substituenteneffekte in den Kernresonanzspektren von 1.3-Diphenyl-Δ2-pyrazolinen und 3-Phenyl-Δ2-isoxazolinen

A metal atom model for the oxidation of carbon monoxide to carbon dioxide. The gold atom-carbon monoxide-dioxygen reaction and the gold atom-carbon dioxide reaction

Helmut Huber

Papers

Stereospecific Conversion of cis-trans Isomeric Aziridines to Open-Chain Azomethine Ylides

Die Addukte primärer und sekundärer Amine an Carbonester der Acetylenreihe und ihre Konfiguration

Cryophotoclustering techniques for synthesizing very small, naked silver clusters Agn of known size (where n = 2-5). The molecular metal cluster-bulk metal particle interface

1.3-Dipolare Cycloadditionen, XXX. Substituenteneffekte in den Kernresonanzspektren von 1.3-Diphenyl-Δ2-pyrazolinen und 3-Phenyl-Δ2-isoxazolinen

A metal atom model for the oxidation of carbon monoxide to carbon dioxide. The gold atom-carbon monoxide-dioxygen reaction and the gold atom-carbon dioxide reaction