Philipp Ritzert

PhD Student
Member of the GRK2516
Group: Prof. Regine von Klitzing, TU Darmstadt Physics
Contact: E-mail, Web

Research Project Area A: Nanoparticles – Experiments
Controlling Composite Material Formation From Gold Nanoparticles and Polymer Brushes

Nanocomposite materials based on inorganic inclusions inside an organic matrix are employed in various fields, as combining both material classes facilitates high versatility of mechanical, optical and chemical properties, while simultaneously covering component drawbacks, e.g. toxicity of many inorganic compounds. The long-term goal of our project aims to provide an approach to manufacture nanocomposite materials with controlled structure. The model system consists of gold nanoparticles self-assembling into a polymer brush matrix. Control of the structure exerted by addition of various salts, thus, utilising salt concentration and ion-specific effects to guide the assembly process.
Investigation involves three steps: gold nanoparticles freely suspended in water exposed to sodium salts with varying anion and concentration; attachment of gold nanoparticles to a polymer brush matrix and characterisation of the response to the sodium salt solutions as before; targeted manipulation of gold particle assembly in a composite material based on the prior characterisation. The Figure shows the aging of gold nanoparticles in water for various sodium salts and concentrations. Especially at intermediate salt concentrations ion-specific effects dominate the response. Figure 2 shows the surface topography of composite materials of polymer brushes and gold nanoparticles before and after immersion in NaSCN solution. Immersion clearly triggered aggregation of gold nanoparticles.

Fig. 1 Gold nanoparticle suspensions (5 nm, citrate functionalized) containing varying sodium salt types of different concentration: directly after mixing (upper) and 12 h later (lower). The samples are ordered from left to right with increasing salt concentration and size of the anion (F, Cl, Br, I, SCN).

Fig. 2 Surface topography of composite materials of poly(N-isopropylacrylamide) brushes and gold nanoparticles (5 nm, citrate functionalized) before (left) and after (right) immersion in 300 mM NaSCN solution.