The functionality of liquid-liquid interfaces formed between two immiscible electrolyte solutions (ITIES) can be markedly enhanced by modification with supramolecular assemblies or solid nanomaterials. The focus of this Review is recent progress involving ITIES modified with floating assemblies of gold nanoparticles or "nanofilms". Experimental methods to controllably modify liquid-liquid interfaces with gold nanofilms are detailed. Also, we outline an array of techniques to characterize these gold nanofilms in terms of their physiochemical properties (such as reflectivity, conductivity, catalytic activity, or plasmonic properties) and physical interfacial properties (for example, interparticle spacing and immersion depth at the interface). The ability of floating gold nanofilms to impact a diverse range of fields is demonstrated: in particular, redox electrocatalysis, surface-enhanced Raman spectroscopy (SERS) or surface plasmon resonance (SPR) based sensors, and electrovariable optical devices. Finally, perspectives on applications beyond the state-of-the-art are provided.

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The complexation reactions between strontium (Sr2+) and octyl(phenyl)‐N,N‐diisobutylcarbamoylmethylphosphine oxide (CMPO) were studied at the aqueous|1,2‐dichloroethane (w|DCE) and aqueous|room‐temperature ionic liquid (w|RTIL) microinterfaces, in order to understand its extraction in reprocessing spent nuclear fuels, remediation of environmental contamination, and potential radiological isotope feed stock for 90Y from its isotope 90Sr in fission byproducts. The stoichiometry (or metal to ligand ratios) and overall complexation constant (β) for these reactions at these two interfaces are described herein. Two stoichiometries at the w|DCE interface were discovered, that is, [Sr(CMPO)2]2+ and [Sr(CMPO)3]2+ with β values of 4.5×1019 and 5.5×1025, respectively. Only one stoichiometry was observed at the w|RTIL interface: [Sr(CMPO)3]2+ with β equal to 1.5×1034. The larger complexation constant for [Sr(CMPO)3]2+ at the w|RTIL interface than those found at the w|DCE interface supported the previous observation of a greater distribution ratio in the aqueous–RTIL metal extraction than that in the aqueous–alkane processing. The kinetics of the reactions at the w|RTIL interface was slow. The stoichiometries at the w|DCE interface were confirmed using biphasic electrospray ionization mass spectrometry (BESI‐MS) as well as direct injection of Sr2+ and CMPO mixture by means of a “shaking flask” experiment to conventional ESI‐MS.

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Single nanoparticle (NP) electrochemistry detection at a micro liquid|liquid interface (LLI) is exploited using the catalyzed oxygen reduction reaction (ORR). In this way, current spikes reminiscent of nanoimpacts were recorded, which corresponded to electrocatalytic enhancement of the ORR by Pt NPs. The nature of the LLI allows exploration of new phenomena in single NP electrochemistry. The recorded impacts result from a bipolar reaction occurring at the Pt NP straddling the LLI. O reduction takes place in the aqueous phase, while ferrocene hydride (Fc-H ; a complex generated upon facilitated interfacial proton transfer by Fc) is oxidized in the organic phase. Ultimately, the role of reactant partitioning, NP bouncing, or the ability of NPs to induce Marangoni effects, is demonstrated.

Initial oxygen concentration (ref. [2-4]) DMFc D 7.26 × 10 −6 cm•s −1 Diffusion coefficient of DMFc and DMFc + (ref. [5]) 2 O D 2.76 × 10 −5 cm•s −1 Diffusion coefficient of O2 (ref. [2]) ' OH w o o φ − ∆ ; however, to make the simulated CVs symmetric, and for the sake of convenience, −0.696 V was employed. 2 Component 1 (comp1) 2.1 Definitions 2.1.1 Variables Variables 3 Selection Geometric entity level Boundary Selection Boundary 2 Name Expression Description intcpl_source_Ibar pi*(rd^2)*F*(chds.ndflux_Maq-chds.ndflux_OHaq + chds.ndflux_Fcplusaq) 2.1.2 Component Couplings Integration 1 Coupling type Integration Operator name intop1 Source selection Geometric entity level Boundary Selection Boundary 2 2.2 Geometry 1 Geometry 1 Units Length unit m Angular unit deg Geometry statistics Property Value Space dimension 1 Number of domains 2 Number of boundaries 3 2.2.1 Interval 1 (i1) Selections of resulting entities Name Value Number of intervals One Left endpoint-0.01 Right endpoint 0 2.2.2 Interval 2 (i2) Selections of resulting entities Name Value Number of intervals One Left endpoint 0 Right endpoint 0.01 2.3 Transport of Diluted Species (chds) Transport of Diluted Species Selection Geometric entity level Domain Selection Domain 1 Equations Settings Description Value Concentration Linear Compute boundary fluxes On Apply smoothing to boundary fluxes On Value type when using splitting of complex variables Real Migration in electric field 0 2.5.1 Size (size) Settings Name Value Maximum element size 5e-6 Minimum element size 6.0E-6 Curvature factor 0.3 Maximum element growth rate 1.3 Custom element size Custom 2.5.2 Edge 1 (edg1) Selection Geometric entity level Remaining

The facilitated ion transfer (FIT) of uranyl or dioxouranium (UO(2)(2+)) was studied electrochemically using a micro interface between two immiscible electrolytic solutions (micro-ITIES) in order to evaluate the complexation stoichiometry and complexation constants (β) of two widely used ligands in spent fuel reprocessing: tributylphosphate (TBP) and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphine oxide (CMPO). For the first time, discrete interfacial complexation reaction steps of varying uranyl to the two ligands ratios were resolved using the micro-ITIES hosted at the tip of a 25 μm diameter glass capillary. Two stoichiometries for UO(2)NO(3)TBP(n)(+) were determined including n = 3 and 4 with β values of 3.2 × 10(11) and 3.9 × 10(13), respectively. Subsequently, three distinct complexation reactions of CMPO with UO(2)(2+) were discovered corresponding to UO(2)NO(3)CMPO(2)(+), UO(2)NO(3)CMPO(3)(+), and UO(2)CMPO(5)(2+) whose respective complexation constants were determined to be 8.0 × 10(11), 8.8 × 10(14), and 6.5 × 10(32). The participation of nitrate anions in these complexation reactions is also discussed.