Electrovariable Gold Nanoparticle Films at Liquid-Liquid Interfaces: from redox electrocatalysis to Marangoni-shutters
Control over physcial properties of nanoparticle assemblies at a liquid-liquid interface is a key technological advancement to realize a dream about smart elevtrovariable nanosystems. Electrified interfaces, such as the interface between two immiscible electrolytes solutions (ITIES), are almost an ideal platform to realize this dream. Here, we show that the Galvani potential difference across soft interfaces can be effectivelly used to manipulate: (i) the reactivity of gold nanoparticle assemblies by varying the Fermi level (both chemically and electrochemically); and (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 ITIES. As expected, the direct adsorption of gold nanoparticles at the interface modifies the kinetics of the ET reaction (so-called, interfacial redox electrocatalysis), however it did not lead to the 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 of 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 plasmonics did not have diffusion limitation in comparison with adsorption/desorption of nanoparticles and the entire movement of nanoparticles assemblies happened almost instantly (within a second). It opens a fresh view on electrovariable plasmonics and propose new opportunities to create smart nanosystems at ITIES driven with electric field.