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

Abstract

Control over the physical properties of nanoparticle assemblies at a liquid-liquid interface is a key technological advancement to realize the dream of smart electrovariable nanosystems.Electrified interfaces, such as the interface between two immiscible electrolytes solutions (ITIES), are almost an ideal platform for realizing this dream. Here, we show that the Galvani potential difference across soft interfaces can be effectively used to manipulate: (i) the reactivity of gold nanoparticle assemblies through varying the Fermi level (both chemically and electrochemically); (ii) the location distribution of the nanoparticles at the liquid-liquid interface. In the first case, in addition to our previous studies on electron transfer reactions (ET) across the ITIES, we used intensity modulated photocurrent spectroscopy (IMPS) to study the kinetics of photo-induced electrochemical reactions at the ITIES. As expected, the direct adsorption of gold nanoparticles at the interface modifies the kinetics of the ET reaction (socalled, interfacial redox electrocatalysis), however it did not lead to an increased photocurrent by "plasmonic enhancement". Rather, we found that the product separation depends on double layer effects while the product recombination is controlled by the Galvani potential difference between the two phases. In the second case, we demonstrated that polarizing the ITIES caused migration of gold nanoparticles from the middle region of the cell to its periphery. We called such systems "Marangoni-type shutters". This type of electrovariable plasmonic system did not experience diffusion limitation in terms of the adsorption/ desorption of nanoparticles and the entire movement of nanoparticle assemblies happened almost instantly (within a second). It opens a fresh view on electrovariable plasmonics and presents new opportunities to create smart nanosystems at the ITIES driven with an electric field.

Redox Electrocatalysis of Floating Nanoparticles: Determining Electrocatalytic Properties without the Influence of Solid Supports

“…111 Also, IMPS has been used recently to study the role of the NPs as redox electrocatalysts in interfacial reaction between DMFc and water soluble zwitter-porphyrin (ZnDMPyDSPP). 112 Authors demonstrated that the presence of gold nanoparticles at ITIES negates kinetic limitation for the interfacial reactions, which corroborates with previous studies. 9,84 An interesting new field is photo-induced redox electrocatalysis [113][114][115] and redox catalysis 116,117 for synthesis of solar fuels.…”

“…In this case, surface second harmonic generation (SSHG) and time-resolved SSHG may provide detailed information on molecule configurations and positioning at the interface, whereas dynamics of photoresponses (kinetic constants of electron transfer) upon heterogeneous quenching at the ITIES can be probed by intensity modulated photocurrent spectroscopy (IMPS), as was shown for of ZnTPPC and ferrocene derivatives . Also, IMPS has been used recently to study the role of NPs as redox electrocatalysts in interfacial reaction between DMFc and water-soluble zwitter-porphyrin (ZnDMPyDSPP) . The authors demonstrated that the presence of gold NPs at ITIES negates kinetic limitation for the interfacial reactions, which corroborates with previous studies. , …”

Mimicking the Microbial Oxidation of Elemental Sulfur with a Biphasic Electrochemical Cell

“…[21,23,24] Usually the surface is not homogeneously covered, significant aggregation of particles takes place at the interface and potential cycling can induce movement of the particles generating an interfacial convection (interfacial stirring). [25] Citrate ions are typically used to stabilize AuNP suspensions in bulk aqueous solutions. [26] However, such suspensions are very stable and, due to inter-particle electrostatic repulsion, the AuNPs rarely deposit in significant numbers at the L|L interface on contacting the aqueous phase with an immiscible organic solvent.…”

Interfacial Synthesis: Morphology, Structure, and Properties of Interfacial Formations in Liquid–Liquid Systems

“…Controlled assembly of molecules and nano-objects and in situ electrogeneration of nanomaterials and membranes are possible [10]. It was shown that the Galvani potential difference at the ITIES can be effectively used to manipulate the reactivity of gold nanoparticles by varying the Fermi level (both chemically and electrochemically) or the position of nanoparticles at the liquid-liquid interface [62][63][64]. It was established that the classical electroanalytical method with a solid electrode can be directly transferred to ITIES, which makes it possible to easily trace and interpret reversible charge transfer reactions [65].…”