Gold Nanofilm Redox Catalysis for Oxygen Reduction at Soft Interfaces

Abstract

A B S T R A C TFunctionalization of a soft or liquid-liquid interface by a one gold nanoparticle thick "nanofilm" provides a conductive pathway to facilitate interfacial electron transfer from a lipophilic electron donor to a hydrophilic electron acceptor in a process known as interfacial redox catalysis. The gold nanoparticles in the nanofilm are charged by Fermi level equilibration with the lipophilic electron donor and act as an interfacial reservoir of electrons. Additional thermodynamic driving force can be provided by electrochemically polarising the interface. Using these principles, the biphasic reduction of oxygen by a lipophilic electron donor, decamethylferrocene, dissolved in a,a,a-trifluorotoluene was catalysed at a gold nanoparticle nanofilm modified water-oil interface. A recently developed microinjection technique was utilised to modify the interface reproducibly with the mirror-like gold nanoparticle nanofilm, while the oxidised electron donor species and the reduction product, hydrogen peroxide, were detected by ion transfer voltammetry and UV/vis spectroscopy, respectively. Metallization of the soft interface allowed the biphasic oxygen reduction reaction to proceed via an alternative mechanism with enhanced kinetics and at a significantly lower overpotential in comparison to a bare soft interface. Weaker lipophilic reductants, such as ferrocene, were capable of charging the interfacial gold nanoparticle nanofilm but did not have sufficient thermodynamic driving force to significantly elicit biphasic oxygen reduction.

Individual Detection and Characterization of Non‐Electrocatalytic, Redox‐Inactive Particles in Solution by using Electrochemistry

“…Also, based on the studies of ensembles of metallic nanoparticles adsorbed at ITIES, the feasibility of their individual detection by using microinterfaces has been proven very recently . For this, an electrocatalytic amplification approach has been followed such that a biphasic electron transfer reaction is mediated by the particle as it collides and adsorbs at the interface, acting as a bipolar nanoelectrode (see Scheme B).…”

Self-healing gold mirrors and filters at liquid–liquid interfaces

“…[45][46][47] Finally, these nanofilms were used to achieve electrocatalysis at electrically polarized liquid-liquid interfaces. 48,49 Recently, our group introduced a facile biphasic method to selfassemble nanofilms of AuNPs at water-1,2-dichloroethane (DCE) interfaces with controllable interfacial AuNP surface coverages ( A u N P i n t  ). 24 Briefly, a lipophilic species (tetrathiafulvalene; TTF) was present in the DCE phase and contacted with an aqueous solution of citrate-stabilized AuNPs.…”

Electrovariable gold nanoparticle films at liquid–liquid interfaces: from redox electrocatalysis to Marangoni-shutters

“…For example, the Fermi level of nanoparticle assemblies can be tuned and manipulated with an external electric eld [13][14][15][16] to perform various electrochemical and electron transfer reactions. 17,18 On the other hand, the physical position of the nanoparticles at the ITIES can be controlled by the electric eld, anticipating the fabrication of "smart" plasmonic mirrors and lters in the near future. 7,8,10 Therefore, to set the canvas of the current article, we shall present here the recent progress in both of the above mentioned topics.…”

“…have been used in the redox electrocatalysis of, for example, oxygen reduction, 18,26 hydrogen evolution 25,27,28 and metal deposition at the ITIES.…”