Charge Transfer across Self-Assembled Nanoscale Metal−Insulator−Metal Heterostructures

Abstract

The kinetics of charge transfer across a metal−insulator−metal architecture is investigated by electrochemical impedance spectroscopy. The insulating component of the architecture is composed by a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA), polyelectrolyte multilayers, and a monolayer of 22 nm SiO2 nanoparticles. The charge transfer to the hexacyanoferrate couple is strongly hindered by the MUA monolayer. The blocking properties effectively vanish with the adsorption of a diluted monolayer of Au nanoparticles (19 nm). Atomic force microscopy and scanning electron microscopy analyses demonstrate that the Au nanoparticles are physically separated from the Au surface by the SiO2 monolayer. The strong electronic communication between the metal nanoparticles and the electrode is rationalized by a nonthermalized transport process involving redox species trapped in the multilayer assembly.

Tracking Nanoelectrochemistry Using Individual Plasmonic Nanocavities

“…This implies that the resistance of each BPT molecule is far below the quantum conductance, as previously suggested 17 . However this disagrees with [19][20][21][22].…”

Some More Observations on the Unique Electrochemical Properties of Electrode–Monolayer–Nanoparticle Constructs

“…However, as this system already challenges expectations the question needs to be answered. It has been answered to some extent by Fermin (where the phenomenon was also observed when silica nanoparticles were present between the electrode and the metal nanoparticles [16] ), by our group (where the underlying electrode is silicon and any direct contact of the nanoparticles to the silicon electrode would cause oxidation of the silicon surface which is not observed [20] ), and by Shapter and co-workers with carbon nanotubes attached to silicon electrodes with an intervening oxide layer . [21] However, all these cases are somewhat different to nanoparticles contacting an alkanethiol SAM.…”

“…[13] In a very elegant series of papers, Fermin and co-workers explored the electrochemistry of electrode-SAM-NP assemblies in considerable detail. [8,[16][17][18] The construct employed involved an alkanethiol modified gold electrode, where the alkanethiol possessed a carboxylic acid at its distal end. To bind gold nanoparticles to this surface, a poly-l-lysine was adsorbed onto the SAM, with the amines of this weak polyelectrolyte serving as coupling points to which gold nanoparticles were bound.…”

A Molecule with Dual Functionality 4‐Aminophenylmethylphosphonic Acid: A Comparison Between Layers Formed on Indium Tin Oxide by In Situ Generation of an Aryl Diazonium Salt or by Self‐Assembly of the Phosphonic Acid

“…This interest has been heightened by recent observations that electron transfer across the organic layer in electrode-organic layer-nanoparticle constructs can be very efficient. In fact studies by us [2] and Fermin and co-workers [3] have shown that for self-assembled monolayers ranging in length between 3 and 11 carbons, the rate of electron transfer appears to be independent of the thickness of the otherwise insulating organic layer. This, somewhat unexpected observation, was very recently explained theoretically by Chazalviel and Allongue [4].…”