Interaction of gold nanoparticles with thermoresponsive microgels: influence of the cross-linker density on optical properties
K. Gawlitza, S.T. Turner, F. Polzer, S. Wellert, M. Karg, P. Mulvaney, R. von Klitzing:
Physical Chemistry Chemical Physics, 15, 15623-15631 (2013)
The interaction of spherical gold nanoparticles (Au-NPs) with microgels composed of chemically crosslinkedpoly-(N-isopropylacrylamide) is reported. Simple mixing of the two components leads toadsorption of the gold particles onto the microgels. Different loading densities can be achieved byvarying the ratio of gold particles to microgel particles. The adsorption of gold nanoparticles is analysedby TEM, UV-Vis absorption spectroscopy and SAXS. The influence of the microgel mesh size on theadsorption of gold nanoparticles is investigated by using microgels with three different cross-linkerdensities. The results suggest a strong relationship between the nanoparticle penetration depth and thecross-linker density. This, in turn, directly influences the optical properties of the colloids due to plasmonresonance coupling. In addition, information about the mesh size distribution of the microgels isobtained. For the first time the change in optical properties by varying cross-linker density andtemperature is directly related to the formation of dimers of gold particles, proven by SAXS.