Environmentally responsive microgels have been subjects of great interest in the last two decades due to their versatile applications in fields like drug delivery, chemical separation and catalysis [1]. In our previous study, thermosensitive polystyrene core-shell microgel particles, in which the core consists of polystyrene whereas the shell consists of a poly (N-isopropylacrylamide) (PNIPA) network, have been used as “nanoreactors” for the deposition of metal nanoparticles (such as Ag, Au, Pd, and Pt) [2]. We demonstrate that the catalytic activity of the metal nanoparticles can be tuned by the volume transition within the microgel by using the catalytic reduction of 4-nitrophenol as the model reaction [3]. In addition to this, thermosensitive Au-PNIPA yolk-shell microgel systems in which a single Au-nanoparticles is immobilized in a hollow shell of PNIPA have been developed [4]. The catalytic selectivity of this hybrid system can be tuned by temperature as is shown by the competitive reduction of the hydrophilic 4-nitrophenol and the hydrophobic nitrobenzene by borohydride.

    In the present study, we report a facile and novel method for the fabrication of Cu2O@PNIPA core-shell nanoreactors using Cu2O nanocubes as the core [5]. The PNIPA shell not only effectively protects the Cu2O nanocubes from oxidation, but also improves the colloidal stability of the system. The Cu2O@PNIPA core-shell microgels can work efficiently as photocatalyst for the decomposition of methyl orange under visible light. A significant enhancement in the catalytic activity has been observed for the core-shell microgels compared with the pure Cu2O nanocubes. Most importantly, the photocatalytic activity of the Cu2O nanocubes can be further tuned by the thermosensitive PNIPA shell. A theory for the diffusion- and solvation-controlled contribution to the reaction rate of such a “nanoreactor” has been also discussed [6]. Hence, the microgel particles present an “active” carrier system for applications in catalysis.