Cyclodextrin modified microgels as “nanoreactor” for the generation of Au nanoparticles with enhanced catalytic activity†
We report a facile and green method for the fabrication of hybrid microgels by the immobilization of catalytically active Au nanoparticles in α-cyclodextrin (α-CD) modified poly(N-vinylcaprolactam) (PVCL) microgels without addition of reducing agent and surfactant. It has been shown that only in the case of α-CD modified microgels metal particles were immobilized inside the colloidal gels, which is due to a coordination of the cyclodextrin molecules to the surface of Au nanoparticles. The PVCL-α-CD-Au composite particles can work efficiently as catalyst for the reduction of aromatic nitro-compounds by using the reduction of 4-nitrophenol (Nip) and 2,6-dimethyl-4-nitrophenol (DMNip) as model reactions. Most importantly, due to the selective binding ability of α-CDs to certain reagents, the synthesized hybrid microgels show different catalytic activity for the target compounds during the catalytic reactions: a significant enhancement in the catalytic activity has been observed for the reduction of Nip, while no obvious effect has been found for the reduction of DMNip.