Atypical catalytic function of embedded gold nanoparticles by controlling structural features of polymer particle in alcohol-rich solvents.

This work demonstrates an in situ approach to incorporate multiple gold nanoparticles (NPs) within a functional-group-free poly(N-isopropylacrylamide) particle and examine their catalytic activity in carbon-carbon forming reactions in pure alcohol and alcohol-rich aqueous solvents under ambient aerobic conditions. The alcohol-rich solvent environments eliminated the cononsolvency effect of the polymer particle template to maintain a fully swollen structure while providing great stability to the embedded gold NPs. In addition, the dispersion of the composites in alcohol solvents efficiently reduced the surface adsorbed stabilizing agent around the embedded gold NPs. Given their high stability and readily accessible surfaces with a minimal physical barrier, these macromolecule-derived composite particles as quasi-homogeneous catalysts exhibited unexpectedly high activity in homocoupling reactions to form C-C bonds. The increased mass transfer capability for reactants and products in pure alcohol and alcohol-rich solvents was also responsible for the highly improved yields in the coupling reactions. Furthermore, the composite particles exhibited great selectivity to solely form targeted compounds without any side products and showed the robustness to be recycled multiple times without losing their catalytic activity in pure alcohol solvent environments. By simply controlling the structural feature of the polymer particle matrix with alcohol solvents, the embedded gold NPs exhibited atypical catalytic activity and selectivity as well as recyclability in C-C bond forming reactions.

In Situ Formation of Gold Nanoparticles within a Polymer Particle and Their Catalytic Activities in Various Chemical Reactions.

Composite materials consisting of nanoscale gold particles and protective polymer shells were designed and tested as catalysts in various chemical reactions. Initially, the systematic incorporation of multiple gold nanoparticles into a poly(N-isopropylacrylamide) particle was achieved by an in situ method under light irradiation. The degree of gold nanoparticle loading, along with the structural and morphological properties, was examined as a function of the amount of initial gold ions and reducing agent. As these gold nanoparticles were physically-embedded within the polymer particle in the absence of strong interfacial interactions between the gold nanoparticles and polymer matrix, the readily-accessible surface of the gold nanoparticles with a highly increased stability allowed for their use as recyclable catalysts in oxidation, reduction, and coupling reactions. Overall, the ability to integrate catalytically-active metal nanoparticles within polymer particles in situ allows for designing novel composite materials for multi-purpose catalytic systems.