We report on the magnetically retrievable multicatalytic colloids with scalable functionalities in aqueous and organic media, which are fabricated via ligand-exchange induced layer-by-layer (LbL) assembly. The advantages of our approach are as follows. First, various catalytic nanoparticles (NPs) can be easily and densely incorporated into the LbL-assembled multilayer shell of the colloids. It implies a single multifunctional colloid can be used as a multicatalyst with highly integrated catalytic properties. Next, the high dispersion stability of multicatalytic colloids in a desired solvent can be obtained by the properties of ultrathin outermost layer of the colloids. Lastly, the strong covalent bonding between functional metal (or metal oxide) NPs and amine-functionalized dendrimers (NH2-dendrimers) within multilayer shells improves the recycling stability of multicatalytic colloids. As model system for this study, we have used Fe3O4, Pd, and TiO2 NPs because these NPs have been widely studied as representative materials for intrinsic magnetic properties and useful catalytic reactions. These hydrophobic NPs were LbL-assembled with amine-functionalized dendrimers (NH2-dendrimers) onto SiO2 colloids using a ligand-exchange reaction between the hydrophobic ligands (such as tetraoctylammonium bromide (TOABr) or oleic acid (OA)) loosely bound to the surface of the metal (or metal oxide) NPs and the amine moities of the dendrimers. The resulting nanocomposite colloids (i.e., SiO2/(NH2-dendrimer/OA-Fe3O4 NP)3/(NH2-dendrimer/TOABr-Pd NP/NH2-dendrimer/OA-TiO2 NP)3) exhibited excellent multicatalytic properties in the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) by TOABr-Pd NP layers in aqueous media, by the Sonogashira reaction by TOABr-Pd NP layers in organic media, and by photocatalysis (degradation of methylene blue) by OA-TiO2 NP layers in aqueous media. Given that the catalytic properties of recyclable colloids reported to date have mostly depended on the property of single kind of catalytic NP layer on the colloids in selective solvent, this approach can provide a basis for the fabrication of recyclable colloids with integrated multicatalytic properties and high dispersion stability in a variety of solvents.

Recyclable multicatalytic colloids with scalable functionalities and high dispersion stability in organic and aqueous media via layer-by-layer assembly

251st National Meeting (2016)

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