11.01.2018

Research Topics

Structure and Properties of Monolayer-Protected Noble Metal Nanoparticles

Characterization of monolayer-protected noble metal nanoparticles is a continuing research area in both chemistry and physics.  Our approach is to use density functional theory to investigate the structure and properties of various monolayer-protected noble metal nanoparticles.  Back in 2006 we established the so-called “Divide and Protect” scheme that stated gold to be in two distinct chemical states in Aux(SR)y nanoparticles: in neutral, “metallic” state in the core and in Au(I) oxidized state in the ligand layer. Since then our research has included various monolayer-protected gold and silver clusters such as "pioneering" cluster types Au25(SR)18-, Au38(SR)24, Au102(SR)44, and Ag44(SR)304-, but also lot of newer cluster types like "computationally monstrous" Ag374(SR)113Br2Cl2. In general, these clusters have illustrated superatom characteristics within their electronic structure, for which shape and symmetry plays also an important role. Our research has extended into monolayer-protected systems made of Au, Ag, Cu, Co, and even main group elements. A mainstay of our research is the use of TDDFT for the determination of optical absorption and circular dichroism spectra that are used for characterization of the clusters. With help of computational methods we are able to reveal the origin of the spectral features and validate the experimental results including geometric structures. We have been successful in predicting the correct geometric structures protected metal nanoclusters even independent from experiment. One of the highlight collaborations during past years has been the breakthrough experiment that demonstrated the success of biological low-dose electron microscopy technique for determination of the 3D atomic structure of the gold core in Au68(SR)32 and Au144(SR)40 3MBA-protected particles, for which we provided theoretical support.

Noble Metal Nanoparticles for Catalysis and Surface Science

We study the reactivity and catalytic activity of noble metal nanoparticles in various environments such as protected by a ligand layer or as supported by solid surfaces. Nanoparticles exhibit catalytic properties due to size effects.  Studies into the reaction pathways and the role of electronic structure in a series of reaction paths offer great insight into the usability of noble metal nanoparticles for catalysis.  In this effort, we have investigated a bare and ligand-protected nanoclusters for various reactions such as CO oxidation. Supported nanosystems are also studied, which presents an opportunity to investigate catalysis on supports and studies in surface science.  We also maintain an ongoing collaboration with the FHI Berlin to understand electronic structure of 2D gold clusters and large islands on thin oxide films that are ideal supports for STM studies.

Gold Nanoparticles for Uses in Biology

We study functionalized thiol-stabilized gold nanoclusters such as Au102(pMBA)44 by large-scale molecular dynamics simulations in biological environment.  Further studies include the interaction of thiol-stabilized gold nanoclusters with capsid proteins of enteroviruses and cell membranes. The motivation for our work comes from a local collaboration inside NSC where such functionalized gold clusters are used for detection of the structure and functions of EV1, CVB3, CVA9 and other enteroviruses. We are currently interested also about development of multifunctional probes using thiol-stabilized nanoclusters for detecting triggers and conditions of biological phenomena in cells.