0000000000478135

AUTHOR

Stefan Knoppe

showing 6 related works from this author

Size Exclusion Chromatography for Semipreparative Scale Separation of Au 38 (SR) 24 and Au 40 (SR) 24 and Larger Clusters

2011

Size exclusion chromatography (SEC) on a semipreparative scale (10 mg and more) was used to size-select ultrasmall gold nanoclusters (2 nm) from polydisperse mixtures. In particular, the ubiquitous byproducts of the etching process toward Au(38)(SR)(24) (SR, thiolate) clusters were separated and gained in high monodispersity (based on mass spectrometry). The isolated fractions were characterized by UV-vis spectroscopy, MALDI mass spectrometry, HPLC, and electron microscopy. Most notably, the separation of Au(38)(SR)(24) and Au(40)(SR)(24) clusters is demonstrated.

ChromatographyChemistrySize-exclusion chromatographyAnalytical chemistry02 engineering and technology010402 general chemistry021001 nanoscience & nanotechnologyMass spectrometry01 natural sciencesHigh-performance liquid chromatography0104 chemical sciencesAnalytical ChemistryNanoclusterslaw.inventionGel permeation chromatographyMatrix-assisted laser desorption/ionizationlawddc:540Electron microscope0210 nano-technologySpectroscopy
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Symmetry breaking in ligand-protected gold clusters probed by nonlinear optics

2016

The first hyperpolarizabilities of [Au25(SR)18](-1/0) and Au38(SR)24 clusters were determined by Hyper-Rayleigh Scattering. A strong dependence on the molecular symmetry was observed, and we explore two strategies to destroy the center of inversion in [Au25(SR)18](-1/0), protection by chiral ligands and alloying of the cluster with silver. This may open new avenues to applications of Au : SR clusters in second-order nonlinear optics.

ta114Condensed matter physicsligandsChemistryScatteringLigandnonlinear opticsNonlinear optics02 engineering and technology010402 general chemistry021001 nanoscience & nanotechnologygold clusters01 natural sciencesMolecular physics0104 chemical sciencesmolecular symmetryMolecular symmetryCluster (physics)General Materials ScienceSymmetry breaking0210 nano-technologyta116Nanoscale
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Au-40(SR)(24) Cluster as a Chiral Dimer of 8-Electron Superatoms: Structure and Optical Properties

2012

We predict and analyze density-functional theory (DFT)-based structures for the recently isolated Au(40)(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 Au(26) 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 Au(25)(SR)(18)(-/0), Au(38)(SR)(24) and Au(102)(SR)(44). The strongly prolate shape of the proposed Au(26) c…

Models MolecularCircular dichroismIcosahedral symmetryDimerShell (structure)Electrons02 engineering and technologyElectronElectronic structure010402 general chemistry01 natural sciencesBiochemistryCatalysischemistry.chemical_compoundColloid and Surface ChemistryCluster (physics)ta114ChemistryCircular DichroismStereoisomerismGeneral Chemistry021001 nanoscience & nanotechnology0104 chemical sciencesCrystallographyTransmission electron microscopyddc:540Quantum Theory0210 nano-technologyDimerizationOrganogold CompoundsJournal of the American Chemical Society
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Role of Donor and Acceptor Substituents on the Nonlinear Optical Properties of Gold Nanoclusters

2018

In recent years, a large number of monolayer-protected clusters (MPCs) have been studied by means of single crystal structure characterization. A central aspect of research on MPCs is the correlation of their interesting optical properties with structural features and the formulation of a theoretical framework that allows interpretation of their unique properties. For this, superatom and jellium models have been proven successful. Little attention, however, has been paid to the influence of the protecting ligands. Here, we investigate the effect of changes in [Au25(SR)18-x(SR′)x]−, where SR′ represents a para-substituted thiophenolate derivative (SPh-4-X). We computed the first hyperpolariz…

Materials scienceJelliumnanoclustersSubstituent02 engineering and technology010402 general chemistrygold clusters01 natural sciencesmonolayer-protected clustersNanoclusterschemistry.chemical_compoundPhysical and Theoretical Chemistryta116ta114ThiophenolSuperatomgoldOrders of magnitude (numbers)021001 nanoscience & nanotechnologyAcceptor0104 chemical sciencesSurfaces Coatings and FilmsElectronic Optical and Magnetic MaterialsCrystallographyGeneral Energychemistry0210 nano-technologySingle crystalThe Journal of Physical Chemistry C
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Electronic Structure and Optical Properties of the Intrinsically Chiral 16-Electron Superatom Complex [Au20(PP3)4]4+

2014

The recently solved crystal structure of the [Au20(PP3)4]Cl4 cluster (PP3: tris(2-(diphenylphophino)ethyl)phosphine) is examined using density functional theory (DFT). The Au20 core of the cluster is intrinsically chiral by the arrangement of the Au atoms. This is in contrast to the chirality of thiolate-protected gold clusters, in which the protecting Au-thiolate units are arranged in chiral patterns on achiral cores. We interpret the electronic structure of the [Au20(PP3)4]Cl4 cluster in terms of the superatom complex model. The 16-electron cluster cannot be interpreted as a dimer of 8-electron clusters (which are magic). Instead, a superatomic electron configuration of 1S(2) 1P(6) 1D(6) …

ta114Condensed matter physicsAbsorption spectroscopyChemistrySuperatomCrystal structureElectronic structureCrystallographyCluster (physics)Density functional theoryElectron configurationPhysical and Theoretical ChemistryChirality (chemistry)ta116The Journal of Physical Chemistry A
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The Role of Donor and Acceptor Substituents on the Nonlinear Optical Properties of Gold Nanoclusters

2018

In recent years, a large number of monolayer-protected clusters (MPCs) have been studied by means of single crystal structure characterization. A central aspect of research on MPCs is the correlation of their interesting optical properties with structural features and the formulation of a theoretical framework that allows interpretation of their unique properties. For this, superatom and jellium models have been proven successful. Little attention, however, has been paid to the influence of the protecting ligands. Here, we investigate the effect of changes in [Au25(SR)18-x(SR′)x]−, where SR′ represents a para-substituted thiophenolate derivative (SPh-4-X). We computed the first hyperpolariz…

nanoclustersgold clusterskultamonolayer-protected clusters
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