Effect of Thiol Chemisorption on the Transport Properties of Gold Nanotubule Membranes

Abstract

An electroless gold deposition method was used to deposit Au nanotubules within the pores of a polycarbonate template membrane. Membranes containing Au nanotubules with inside diameters of 2 and 3 nm were prepared for these studies. Thiols were chemisorbed to the inside tubule walls in order to change the chemical environment within the tubules. The effect of the chemical environment within the tubules on the transport properties of the tubule-containing membrane was investigated. Membranes modified with HS-C(16)H(33) preferentially transported hydrophobic permeant molecules. When a homologous series of permeant molecules was used, the most hydrophobic permeant was preferentially partitioned into and transported by the HS-C(16)H(33) derivatized membrane. In addition, the effect of alkyl chain length (R), in a homologous series of thiols R-SH, was investigated. Hydrophobic permeant molecules were preferentially partitioned into and transported by membranes containing the largest alkyl group. In contrast, membranes modified with HS-C(2)H(4)OH preferentially transported the more hydrophilic permeant pyridine. Finally, we show here that the HS-C(16)H(33) derivatized membrane can be used to separate hydrophobic species from hydrophilic species.

Template Deposition of Metals

“…The principles of electroless deposition in templates are exemplified for Au deposition developed in Martin's laboratory for the template fabrication of NEEs, nanotubes, and other shaped gold nanomaterials (5, 7). The electroless plating of gold (5) Note that if the plating procedure is stopped after a relatively short time, Au nanotubes are formed within the pores (70)(71)(72)(73). To fill the pores completely and obtain nanowires, the electroless plating process must proceed for about 24 h as described above (5).…”

“…In fabricating Au nanotubes, it is also important to control the size of the gold particles that are deposited on the pore walls. This is achieved by controlling the pH of the deposition bath at a value around 10, for example, by adding carbonate buffer (73). After completion of the deposition, it is possible to separate the nanowires or nanotubes from the template membrane (see Section 16.2.3.3) or to keep them in the template.…”

Hybridization-Modulated Ion Fluxes through Peptide-Nucleic-Acid- Functionalized Gold Nanotubes. A New Approach to Quantitative Label-Free DNA Analysis

“…16 The nanopores were prepared by electroless Au plating of track etch polycarbonate membranes. 10 In order to obtain regular pore diameters and better control of the plating process, the original recipe was slightly modified in that the membranes were dried in N 2 atmosphere before placing them in the Au plating solution of pH 10 kept at 1 °C. As shown by field emission scanning electron micrographs of the resulting membranes, Au deposition times of 200 min gave in regular nanopores with close to uniform thickness of the Au layer ( Figure 1B).…”

Ion transport controlled by nanoparticle-functionalized membranes

“…Perhaps most importantly, we have demonstrated a desirable and readily attainable feature of specifically tailoring transport through a suitable choice of encapsulating ligand chemically absorbed to the NP surface. In this regard, we are able to achieve a desired functionality in a manner similar to, but distinctly different from, those using self-assembled monolayers (SAMs) [35][36][37][38][39][40][41] , b a (1), under the assumption of a fixed membrane charge density, |X|. Deviations to the model are most prevalent at low electrolyte concentration, resulting from the fact that |X| is not a constant, but depends on the electrolyte concentration as shown in the inset.…”

“…Here by utilizing particles encoded a priori with the desired functionality, we are able to bypass the requirement of a favourable surface chemistry in order to bind the molecules to the surface of the porous substrate itself, or any additional steps coating the substrate with a metal such as gold [38][39][40][41] . Owing to the flexibility by which ligated NPs can be synthesized, including both the core materials themselves and the encapsulating ligands 43,44 , we believe the approach outlined here can be generalized to a similar set of functionalities as their SAM counterparts for different core materials.…”