Flexible Synthesis of Stable Gold Nanoparticle Clusters

• Applicant: Dr. Florian Schulz
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 290481307

In the nanoparticle synthesis of various materials a high level of shape- and size-control has been achieved today. Increasing research interest now focuses on the controlled assembly of nanoparticles in two and three dimensions. One hopes, that new properties will arise in nanoparticle ensembles, distinct from the non-interacting nanoparticles. The aim of the proposed project is to develop a robust and flexible protocol for the synthesis of defined clusters from spherical gold nanoparticles. The intended clusters consist of a core-particle, surrounded by equidistant satellite particles. The size of core and satellites is intended to be variable with control over number and distance of satellites. The clusters should be highly stable, but they should also allow for diffusion of analytes into the cluster structure. For the syntheses, mixtures of mono- and heterobifunctional poly(ethylene glycol) (PEG) ligands will be used, that bind to the gold surface of the nanoparticles via thiol groups. In situ creation of dithiocarbamate groups will then allow for binding of additional gold nanoparticles. One important objective of the project is control of the clusters' geometry and the reproducibility of the synthetic route. After basic characterization of the clusters, their potential as a platform for direct surface-enhanced Raman scattering (SERS) and refractometric sensing is to be tested. To this end, the diffusion of analyte molecules with different sizes and hydrophobicities into the cluster structures will be studied. Strong enhancements of the electromagnetic field in areas between particles in close proximity, the so-called hot spots, are the reason for very strong enhancements of Raman scattering and high sensitivity to changes of the refractive index and are directly related to the optical properties of the clusters. Supported by theoretical models, the clusters are therefore to be extensively characterized by spectroscopy to optimize the cluster geometry for analytical applications. By tailoring the surface chemistry of the cluster components the cluster are to be designed and optimized to allow for their application in complex media and detection of challenging analytes. In the final phase of the project, preliminary experiments are to be pursued to explore the applicability of the synthetic strategy for hybrid clusters, e.g. from gold and semiconductor nanoparticles.

• DFG Programme: Research Grants
• International Connection: Spain
• Cooperation Partners: Professor Dr. Holger Lange; Professorin Dr. Doreen Mollenhauer; Privatdozent Dr. Markus R. Wagner