Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 21: Focus: Smart Hydrogels and Hydrogel Based Devices I - organized by Gerald Gerlach, Walter Richtering and Thomas Hellweg
CPP 21.3: Vortrag
Dienstag, 13. März 2018, 10:15–10:30, C 130
Rational design of Ag@PS-PNIPAM core-shell nanoreactors with tunable activity for catalysis — •Daniel Besold1, Sebastian Risse1, Rafael Roa1, Yan Lu1,2, Joachim Dzubiella1,3, and Matthias Ballauff1,3 — 1Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Germany — 2Institut für Chemie, Universität Potsdam, Potsdam, Germany — 3Institut für Physik, Humboldt-Universität zu Berlin, Germany
Nanoreactors containing metal nanoparticles embedded in stimuli-responsive polymers have recently emerged as promising catalytic systems. The polymer coating not only prevents nanoparticle aggregation but also controls the catalytic activity by changing the local environment for the reactants. For this work we synthetized thermosensitive core-shell nanoreactors, composed of a polystyrene core in a PNIPAM microgel shell, in which silver nanoparticles are immobilized. In this system, we study the catalytic reduction of 4-nitrophenol by borohydride ions. Our kinetic analysis is based on UV-Vis spectroscopic techniques. The spectra are deconvoluted by the Levenberg-Marquardt algorithm which provides us with the concentration-time dependency of the species involved in the reaction. We tune the catalytic activity of the silver nanoparticles by tuning the temperature of the system. We find two distinct regimes in the catalytic rate at temperatures below and above the volume transition of the PNIPAM shell. By means of a modified Langmuir-Hinshelwood mechanism which accounts for electrostatic effects on the reactant adsorption, we attribute the changes in the rate to changes in the reactant partitioning in the shell.