- Previous Article
- Next Article
- Table of Contents
Advanced Materials, Vol.13, No.18, 1351-1362, 2001
Controlling ion-transport selectivity in gold nanotubule membranes
We have developed a new class of synthetic membranes that consist of a porous polymeric support. This support contains an ensemble of gold nanotubules that span the complete thickness of the support membrane. The support is a commercially available microporous polycarbonate filter with cylindrical nanoscopic pores. The gold nanotubules are prepared via electroless deposition of Au onto the pore walls, and tubules that have inside diameters of molecular dimensions (<1 nm) call be prepared. Hence, these membranes are a new class of molecular sieves. We review in this paper the ion-transport properties of these Au nanotubule membranes. We will show that these membranes call be cation-permselective or anion-permselective, and that the permselectivity can be reversibly switched between these two states. Ion permselectivity can be introduced by two different routes. The first entails chemisorption of all ionizable thiol, e.g., a carboxylated ammonium-containing thiol to the Au tubule walls. If the thiol contains both of these functionalities (e.g., the amino acid cysteine), the permselectivity call be reversibly switched by varying the pH of the contacting solution phase. Ion permselectivity, can also he introduced by, potentiostatically charging the membrane in all electrolyte solution. By applying excess negative charge, cation permselective membranes are obtained, and excess positive large yields anion permselective membranes. In this case the permselectivity can be reversibly, switched by changing the potential applied to the membrane.