Development of ultrafiltration membrane by stacking of silver nanoparticles stabilized with oppositely charged polyelectrolytes

We have developed a nanoparticle (NP)-stacked ultrafiltration membrane with a very thin active separation layer, by using electrostatic interaction of polyelectrolyte-stabilized NPs. Oppositely charged Ag NPs were prepared by the seed-growth method using either cationic or anionic polyelectrolytes as stabilizing agents. The Ag NPs were stacked onto an inorganic supporting membrane using layer-by-layer (LbL) deposition. By controlling the ionic strength of the NP dispersion and increasing the number of LbL dipping cycles, a stacked layer of NPs was successfully formed onto the supporting membrane. The membrane fabricated with 30 cycles of LbL dipping had a water permeability of 9.5 m3 m−2 day−1 atm−1 and a molecular weight cutoff of 500 kDa for dextran. This value was comparable to commercial membranes, suggesting applications for water treatment and solute separation.