Engineered Gold Nanotube Membranes for Molecular Separations L. Velleman 1 , J.G. Shapter 1 , and D. Losic 2 1 Flinders University, School of Chemistry, Physics and Earth Sciences, Bedford Park, Adelaide, SA 5042 2 University of South Australia, Ian Wark Research Institute, Mawson Lakes Campus, Mawson Lakes, Adelaide, SA 5095 Abstract—An electroless gold deposition method was used to fabricate gold nanotubes within the pores of polycarbonate and porous alumina template membranes. This approach provides control over the pore size of the membrane, with pore sizes being reduced to molecular dimensions. The effect of the pore size and surface chemistry on the transport properties of gold nanotube membranes has been explored. By modifying the membrane with a highly hydrophobic thiol, the separation of hydrophobic and hydrophilic molecules was achieved. Keywords- gold nanotube membrane, electroless gold plating, permeation, molecule separation. I. INTRODUCTION Nanoporous membranes have shown great promise in the field of chemical separations, adsorption, biosensing, catalysis and drug delivery due to their porosity, high surface area, rich surface chemistry and simple up-scaling. Electroless deposition has recently been used to finely coat porous membranes with gold, forming gold nanotubes within the pores [1-3]. By controlling the deposition time, the inner pore diameter of the membrane can be reduced to molecular dimensions (~1nm) thus providing a means to separate molecules by size. The appeal of gold nanotube membranes for molecular separation is primarily related to properties of the gold such as its chemical inertness, temperature stability, conductivity and the ability to functionalise in order to tailor chemical surface properties. In recent years, studies have been devoted to improve the transport and separation properties of the gold nanotube membranes to perform a variety of separations including gas, ion, organic and biomolecule (DNA, protein) separation [2, 4]. This study is focused on the fabrication, chemical modification and characterisation of gold nanotube membranes using various porous membranes as a template. The pore size and surface chemistry is tailored to optimize their transport and selectivity properties. Surface modification of gold nanotube membranes using a highly hydrophobic self-assembled monolayer (SAM) of perfluorodecanethiol is applied for the first time to explore the selectivity towards hydrophobic/hydrophilic molecules (Fig.1). Figure 1. Schematic of the electroless plating process used to form gold nanotube membranes. The chemical selectivity of these gold membranes can be tailored with the addition of self-assembled monolayers such as perfluorodecanethiol (PFDT). II. EXPERIMENTAL A. Materials The polycarbonate (PC) membranes (pore size 30nm, 80nm, 200nm and 800nm) and porous alumina (PA) membranes (Anodisc, pore size 200nm) were purchased from Whatman. The gold plating solution (Oromerse SO Part B) was obtained from Technic, Inc. (USA). Dyes, Tris(2,2’- bipyridyl)ruthenium(II) (Rubpy), pinacyanol chloride (PCN) and rose bengal (RB) were supplied from Aldrich. 1H,1H,2H,2H-perfluorodecanethiol (CF 3 (CF 2 ) 7 CH 2 CH 2 SH, PFDT). Dichloromethane, tin (II) chloride, trifluoroacetic acid, nitric acid, ammonia, methanol, formaldehyde, sodium sulfite, sodium bicarbonate, sulfuric acid, and ethanol 97% were purchased from Sigma-Aldrich (Australia) and used as received. Silver nitrate was obtained from Proscitech (Australia). 3-(triethoxysilyl)propylsuccinic anhydride was obtained from Gelest, (USA). Milli-Q water (18MΩ) was used for rinsing and preparation of all solutions. 1-4244-1504-7/08/$25.00  2008 IEEE ICONN 2008 86