Preparation of carboxylated silver nanoparticles via a reverse micelle method and covalent stacking onto porous substrates via amide bond formation.

Covalently bound silver nanoparticle (Ag NP)-stacked ultrafiltration membranes were fabricated using carboxylated Ag NPs via amide bond formation. Carboxylated Ag NPs were prepared by a reverse micelle method using 3-mercaptopropionic acid as a NP stabilizer containing carboxyl groups. NP formation was confirmed by transmission electron microscopy and evaluation of the surface plasmon resonance. The thus-prepared spherical and monodisperse Ag NPs were stacked onto an aminated porous aluminum substrate by amide bond formation between the amino groups on the substrate surface and the carboxyl groups on the NP surface via an active ester method. The surface morphology was observed by scanning electron microscopy. To aminate the substrate surface, the substrate was treated with three kinds of aminosilanes. The type of aminosilane affected the NP-stacking behavior. The water permeability and rejection performance of the fabricated NP-stacked substrates as ultrafiltration membranes was evaluated using a cross-flow membrane filtration system. Although the substrate stacked with a single layer of NPs showed only slight rejection performance, that with a multilayer of NPs acted as an ultrafiltration membrane and had a molecular weight cutoff of 500 kDa for dextran. [ABSTRACT FROM AUTHOR]