world’s thinnest nanofiltration membrane

World’s Thinnest Nanofiltration Membrane Fabricated from Sheets of Self-Assembled Gold Nanoparticles

Typical separation membranes for nanofiltration consist of micron-thick polymer films. Reducing this thickness allows for transport across the membrane at a smaller pressure drop, a major limiting factor in these devices. Made of just four layers of ligated Au nanoparticles for a total thickness of about 30nm, we demonstrated the world’s thinnest nanofiltration membrane thus far. The filtration coefficient of this membrane is ~100x larger than in typical polymer-based nanofiltration systems. At less than 1 atm pressure drop, it rejects all molecules with sizes above 1.7nm and controls the passage of smaller molecules depending on whether they are charged or not. Guided by atomistic molecular dynamics simulations, we found that molecular transport occurs through pore-like regions between close-packed nanoparticles and that dielectric exclusion dominates the charge-dependent rejection. Since particle size, ligand coating, and packing geometry can all be adjusted, this research opens up possibilities for a new class of versatile filtration and separation systems based on ultrathin, freestanding nanoparticle sheets.

Heinrich Jaeger, University of Chicago, DMR 0907075

charged

uncharged

Jinbo He, Xiao-Min Lin1, Henry Chan2, Lela Vukovic2, Petr Kral2, Heinrich Jaeger, ”Diffusion and Filtration Properties of Gold Nanoparticle Membranes”, Nano Letters, published online May 6, 2011 http://pubs.acs.org/doi/full/10.1021/nl200841a 1Argonne Nat’l Lab 2Univ of Illinois at Chicago