Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Crystallisation, Nucleation and Self assembly

CPP 29.2: Topical Talk

Wednesday, March 28, 2012, 15:30–16:00, C 243

2D and 3D assembly of polymer-coated gold nanoparticles — •Matthias Karg — Department of Chemistry, University of Bayreuth, Bayreuth, Germany

The assembly of metal nanoparticles into superstructures with mm or even cm dimensions is a challenging scientific task.

We coated gold nanoparticles with cross-linked polymer shells resulting in core-shell particles with well-defined structures[1]. The polymer shells are composed of poly-N-isopropylacrylamide (PNIPAM), which is a thermoresponsive material. Due to these shells, the effective particle volume of the nanoparticles is increased significantly. This allows reaching high volume fractions with comparably low particle numbers.

Crystallization was observed over a broad range of particle concentrations at room temperature[2]. Upon an increase in temperature, the PNIPAM shells shrink and the overall particle volume fraction decreases. This causes melting of the crystals in a certain concentration range. Upon cooling, crystallization occurs again, once a critical volume fraction is reached. These melting/recrystallization processes were observed to occur with very high reproducibility as will be demonstrated in this contribution. This unique behaviour is interesting for applications in sensing and optics since it presents a new pathway towards the controlled preparation of large-scale 'nanocrystal-doped' photonic crystals.

[1] M. Karg, S. Jaber, T. Hellweg, P. Mulvaney, Langmuir 2011, 27, 820 [2] M. Karg, T. Hellweg, P. Mulvaney, Adv. Funct. Mater. DOI: 10.1002/adfm.201101115