Electron and ion transport through multilayers of Au nanoclusters covered by self-assembled monolayers

Abstract

Two types of gold nanoclusters (GNCs), one covered by self-assembled monolayers (SAMs) of mercaptoundecanoic acid (MUA), hexanethiol (C 6 SH), and ferrocenylhexanethiol (FcC 6 SH), MHF-GNC, and the other with MUA and C 6 SH, MH-GNC, were used for the construction of ten GNC layers of two different sequences on an MUA modified Au (111) surface based on the carboxylate/polycation (poly(allylamine hydrochloride) :PAH)/carboxylate electrostatic interaction. MHF-GNC was placed either as the layer closest to the gold electrode, i.e., the first layer, or as the outermost layer with MH-GHC in the other layers. A quasi-reversible redox peak with a constant charge corresponding to the redox of the ferrocene moiety of the MHF-GNC monolayer was observed at both electrodes, showing electrons and perchlorate ions could be transferred through the MH-GNC/PAH multilayers.Cross-sectional transmission electron microscopy revealed that the size of the immobilized GNC was almost same as that in solution and well-separated GNCs were dispersed rather uniformly within the polymeric matrix. The incorporation of perchlorate ion upon the oxidation of the ferrocene moiety of the MHF-GNC was demonstrated by electrochemical quartz microbalance measurement. Based on the above results, the charge transfer mechanism in the GNC multilayers was discussed.2

SERS in PAH-Os and gold nanoparticle self-assembled multilayers

“…Hodak et al 5 introduced redox enzymes deposited with a polycationic redox mediator in ordered multilayers using this technique and the redox mediation of glucose oxidase in self-assembled structures formed with the enzyme and poly͑allylamine͒ modified with Os͑byp͒ 2 ClPyCHO ͑PAH-Os͒ has been studied. 6,7 The assembly of derivatized gold nanoparticles with polyelectrolyte self-assembled multilayers has been studied by Song et al,8 in particular as regard the directional electron transport. The incorporation of biomolecules with direct electrical contact to nanoparticles has been introduced by Xiao et al by wiring glucose oxidase to Au nanoparticles.…”

Construction of multilayers of bare and Pd modified gold nanoclusters and their electrocatalytic properties for oxygen reduction

“…GNCs covered by C 6 SH, FcC 8 SH and MUA SAMs (MHF-GNCs) were prepared by the procedure reported previously [20][21][22][23][24][25]: C 6 SH SAM protected GNCs were synthesized by the two-phase method of Brust et al [27]. Then, FcC 8 SH and MUA were introduced sequentially onto the surface of the C 6 SH SAM protected GNCs by the place exchange method [28].…”

“…The molar ratio of C 6 SH : FcC 8 SH : MUA on the MHF-GNCs surface was estimated by 1 H-NMR (Hitachi, R-1900, 90 MHz) as 28 : 12 : 60. The core size of the MHF-GNCs was estimated as 1.8 nm by transmission electron microscopy (TEM)(JEOL, JEM-200FX) [22,23].…”

“…A gold RDE was polished to a mirror finish The substrate was dipped first in a 0.1 M NaOH aqueous solution containing 2 mg mL −1 PAH for 5 min and then in an ethanol solution containing 0.15 wt% GNCs for 15 min, with a rinse after each dip. The PAH/GNC dipping cycle was repeated to obtain the PAH/GNC multilayer as shown in scheme 1(a)-(c) [21][22][23][24][25].…”

“…We have already reported the construction of a multilayer of self-assembled monolayer (SAM) protected gold nanoclusters (GNCs) and polyelectrolyte using electrostatic interaction on gold and indium tin oxide (ITO) surfaces, which acted as three-dimensional electrodes [20][21][22][23][24][25]. In this study, a three-dimensional electrocatalytic electrode was constructed by careful removal of the SAM by anodic oxidation, followed by the deposition of a small amount of Pd on the surface of GNCs in the multilayer assembly.…”