Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Nanoparticles and Composite Materials I

CPP 1.8: Vortrag

Montag, 11. März 2013, 12:00–12:15, H34

Photoinduced phase transitions in gold-microgel hybrids — •Sarah T. Turner, Stefan Wellert, and Regine von Klitzing — Stranski Laboratory, Dept. of Chemistry, TU Berlin, Germany

The ability to reversibly switch between a collapsed and expanded state in response to an external stimulus makes hybrid microgels attractive for applications such as sensoric and drug delivery systems. We studied the photoinduced light-to-heat conversion and consequent volume phase transition of hybrid gold-microgels. In order to use such hybrid systems as a potential barrier in polyelectrolyte multilayers, details about the degree of shrinking related to the gold loading and laser intensity are required. An optimal gold nanoparticle concentration per microgel was found to exist, as too low a concentration does not allow enough heat formation to induce a volume phase transition and too high a concentration hinders the full swelling of the microgel below the lower critical solution temperature. The distribution and loading of the gold nanoparticles is investigated via transmission electron microscopy and the change in the plasmon resonance of the gold nanoparticles upon microgel shrinking is investigated by temperature- controlled UV-Vis absorption spectroscopy. The plasmon resonance frequency of the gold nanoparticles was excited by one laser (532 nm) while a second was used to simultaneously measure dynamic light scattering (633 nm) by blocking the scattering signal from the first laser with an optical filter.