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An active droplet system, programmed to repeatedly move autonomously at a specific velocity in a well-defined direction, is demonstrated. Coulombic energy is stored in oversaturated interfacial assemblies of charged nanoparticle-surfactants by an applied DC electric field and can be released on demand. Spontaneous emulsification is suppressed by an increase in the stiffness of the oversaturated assemblies. Rapidly removing the field releases the stored energy in an explosive event that propels the droplet, where thousands of charged microdroplets are ballistically ejected from the surface of the parent droplet. The ejection is made directional by a symmetry breaking of the interfacial assembly, and the combined interaction force of the microdroplet plume on one side of the droplet propels the droplet distances tens of times its size, making the droplet active. The propulsion is autonomous, repeatable, and agnostic to the chemical composition of the nanoparticles. The symmetry-breaking in the nanoparticle assembly controls the microdroplet velocity and direction of propulsion. This mechanism of droplet propulsion will advance soft micro-robotics, establishes a new type of active matter, and introduces new vehicles for compartmentalized delivery.

The influence of the ion transfer on photoinduced electron transfer (ET) reactions was studied on the surface of hyperbranched semiconducting BiVO4 particles spontaneously adsorbed at the liquid‐liquid (L/L) interface between an aqueous LiCl solution and bis(triphenylphosphoranylidene) ammonium tetrakis(pentaflurophenyl)borate (BATB) in 1,2‐dichlorethane. The organic electrolyte was supplemented with [Co(bpy)3](PF6)3 to accept photoexcited electrons from BiVO4 under formation of the corresponding Co(II) complex. The L/L interface was stabilized at the orifice of a micropipette (MP) and allowed to record ion transfer cyclic voltammetry (ITCV) by applying a Galvani potential difference Δowϕ ${{\rm{\Delta }}_o^w \varphi }$ between two reference electrodes in the electrolyte solutions with intermittent illumination by visible light (λ>420 nm). The photogenerated holes caused oxidation of water to O2. Co(II) and O2 were detected at constant Δowϕ ${{\rm{\Delta }}_o^w \varphi }$ at an amperometric microelectrode (ME) facing the orifice of the MP in either the organic or the aqueous electrolyte. The overall current exhibits a photocurrent only in the Δowϕ ${{\rm{\Delta }}_o^w \varphi }$ ‐range, in which the IT of PF6− is kinetically limited. The amperometric detection of photogenerated products followed the same pattern as the photocurrent in the total current. [ABSTRACT FROM AUTHOR]

The recognition of the importance of nanostructures is mainly due to the development of nanotechnology. For further developments in materials sciences, a concept that integrates nanotechnology with material chemistry to fabricate functional materials has to be proposed. Nanoarchitectonics will carry out this task. In nanoarchitectonics, we architect functional material systems from nano-units (atoms, molecules, nanomaterials). The methodology is not specific to any particular material or application. It covers a wide range. Therefore, nanoarchitectonics can be thought of as the method for everything in materials science. As typical demonstrations for usages of nanoarchitectonics, this review paper presents our work on nanoarchitectonics for supercapacitors. We divide it into two categories with different approaches. The first is the development of carbon materials as supercapacitor electrode materials from biomass. The second category is preparing carbon materials using structures created by supramolecular assembly of fullerenes such as C60 and C70. By presenting examples using opposite starting materials, a complex natural material, and an ultimately simple molecule, we will demonstrate the versatility and breadth of possibilities of this approach. [ABSTRACT FROM AUTHOR]

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid's physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase. [ABSTRACT FROM AUTHOR]

Ruddlesden‐Popper (RP) hybrid perovskites have the characteristics of controllable quantum well thickness, excellent stability, and good photoelectric performance. However, traditional space‐limited methods easily induce additional defects at the crystal interface. Herein, a novel swimming top‐down method is proposed for growing high‐quality perovskite single‐crystal sheets in a biphasic liquid–liquid n‐dodecane/γ‐butyrolactone (GBL) system. The (BA)2MAPb2I7 single‐crystal sheet exhibited the lowest defect density on the top surface because of interfacial features, including a flat biphasic confined interface, a large area for GBL molecule diffusion, and sufficient traction for swimming growth. As a typical result, (BA)2MAPb2I7 single‐crystal‐based photodetectors exhibit outstanding weak‐light photoelectric performance with a responsivity of 1.02 A W−1, an external quantum efficiency of 226.9%, and a detectivity of 8.7 × 1012 Jones; these values are 310%, 310%, and 700%, respectively, as high as those of photodetectors obtained by the antisolvent vapor‐assisted crystallization method. [ABSTRACT FROM AUTHOR]

Nanoscale science is becoming increasingly important and prominent, and further development will necessitate integration with other material chemistries. In other words, it involves the construction of a methodology to build up materials based on nanoscale knowledge. This is also the beginning of the concept of post-nanotechnology. This role belongs to nanoarchitectonics, which has been rapidly developing in recent years. However, the scope of application of nanoarchitectonics is wide, and it is somewhat difficult to compile everything. Therefore, this review article will introduce the concepts of liquid and interface, which are the keywords for the organization of functional material systems in biological systems. The target interfaces are liquid–liquid interface, liquid–solid interface, and so on. Recent examples are summarized under the categories of molecular assembly, metal-organic framework and covalent organic framework, and living cell. In addition, the latest research on the liquid interfacial nanoarchitectonics of organic semiconductor film is also discussed. The final conclusive section summarizes these features and discusses the necessary components for the development of liquid interfacial nanoarchitectonics. [ABSTRACT FROM AUTHOR]

The mechanics of capillary force in biological systems have critical roles in the formation of the intra- and inter-cellular structures, which may mediate the organization, morphogenesis, and homeostasis of biomolecular condensates. Current techniques may not allow direct and precise measurements of the capillary forces at the intra- and inter-cellular scales. By preserving liquid droplets at the liquid-liquid interface, we have discovered and studied ideal models, i.e., interfacial liquids and marbles, for understanding general capillary mechanics that existed in liquid-in-liquid systems, e.g., biomolecular condensates. The unexpectedly long coalescence time of the interfacial liquids revealed that the Stokes equation does not hold as the radius of the liquid bridge approaches zero, evidencing the existence of a third inertially limited viscous regime. Moreover, liquid transport from a liquid droplet to a liquid reservoir can be prohibited by coating the droplet surface with hydrophobic or amphiphilic particles, forming interfacial liquid marbles. Unique characteristics, including high stability, transparency, gas permeability, and self-assembly, are observed for the interfacial liquid marbles. Phase transition and separation induced by the formation of nanostructured materials can be directly observed within the interfacial liquid marbles without the need for surfactants and agitation, making them useful tools to research the interfacial mechanics. [ABSTRACT FROM AUTHOR]

Abstract This work compares the electroanalytical performance of two electroanalytical systems based on (1) the glassy carbon electrode (GCE), and (2) the electrified liquid–liquid interface (eLLI), for the detection of fluoroquinolone antibiotic–danofloxacin (DANO). Our aim was to define the optimal conditions to detect the chosen analyte with two employed systems, extract a number of electroanalytical parameters, study the mechanism of the charge transfer reactions (oxidation at GCE and ion transfer across the eLLI), and to provide physicochemical constants for DANO. Detection of the chosen analyte was also performed in the spiked milk samples. To the best of our knowledge, this is the first work that directly compares the electroanalytical parameters obtained with solid electrode (in this case GCE) and eLLI. We have found that for DANO the latter provides better electroanalytical parameters (lower LOD and LOQ) as well as good selectivity when the milk was analyzed.

This work compares the electroanalytical performance of two electroanalytical systems based on (1) the glassy carbon electrode (GCE), and (2) the electrified liquid–liquid interface (eLLI), for the detection of fluoroquinolone antibiotic–danofloxacin (DANO). Our aim was to define the optimal conditions to detect the chosen analyte with two employed systems, extract a number of electroanalytical parameters, study the mechanism of the charge transfer reactions (oxidation at GCE and ion transfer across the eLLI), and to provide physicochemical constants for DANO. Detection of the chosen analyte was also performed in the spiked milk samples. To the best of our knowledge, this is the first work that directly compares the electroanalytical parameters obtained with solid electrode (in this case GCE) and eLLI. We have found that for DANO the latter provides better electroanalytical parameters (lower LOD and LOQ) as well as good selectivity when the milk was analyzed. [ABSTRACT FROM AUTHOR]

The recognition of the importance of nanostructures is mainly due to the development of nanotechnology. For further developments in materials sciences, a concept that integrates nanotechnology with material chemistry to fabricate functional materials has to be proposed. Nanoarchitectonics will carry out this task. In nanoarchitectonics, we architect functional material systems from nano-units (atoms, molecules, nanomaterials). The methodology is not specific to any particular material or application. It covers a wide range. Therefore, nanoarchitectonics can be thought of as the method for everything in materials science. As typical demonstrations for usages of nanoarchitectonics, this review paper presents our work on nanoarchitectonics for supercapacitors. We divide it into two categories with different approaches. The first is the development of carbon materials as supercapacitor electrode materials from biomass. The second category is preparing carbon materials using structures created by supramolecular assembly of fullerenes such as C60 and C70. By presenting examples using opposite starting materials, a complex natural material, and an ultimately simple molecule, we will demonstrate the versatility and breadth of possibilities of this approach.

[Display omitted] Healable electronic skins, an essential component for future soft robotics, implantable bioelectronics, and smart wearable systems, necessitate self-healable and pliable materials that exhibit functionality at intricate interfaces. Although a plethora of self-healable materials have been developed, the fabrication of highly conformal biocompatible functional materials on complex biological surfaces remains a formidable challenge. Inspired by regenerative properties of skin, we present the self-assembled transfer-printable liquid metal epidermis (SALME), which possesses autonomous self-healing capabilities at the oil–water interface. SALME comprises a layer of surfactant-grafted liquid metal nanodroplets that spontaneously assemble at the oil–water interface within a few seconds. This unique self-assembly property facilitates rapid restoration (<10 s) of SALME following mechanical damage. In addition to its self-healing ability, SALME exhibits excellent shear resistance and can be seamlessly transferred to arbitrary hydrophilic/hydrophobic curved surfaces. The transferred SALME effectively preserves submicron-scale surface textures on biological substrates, thus displaying tremendous potential for future epidermal bioelectronics. [ABSTRACT FROM AUTHOR]

Oil-water interfaces that are created by confining a certain amount of oil in a square shaped pixel (∼200 x 200 μ m 2 with a height of ∼10 μm) topped by a layer of water, have a curvature that depends on the amount of oil that happens to be present in the confining area. Under the application of an electric field normal to the interface, the interface will deform due to inhomogeneities in the electric field. These inhomogeneities are expected to arise from the initial curvature of the meniscus, from fringe fields that emerge at the confining pixel walls and, if applicable, from interfacially adsorbed particles. We model the shape of the confined oil-water interface invoking capillarity and electrostatics. Furthermore, we measure the initial curvature by tracking the position of interfacially adsorbed particles depending on sample tilt. We found that the pixels exhibited meniscus curvature radii ranging from 0.6-7 mm. The corresponding model based minimum oil film thicknesses range between 0.7 and 9 μm. Furthermore, the model shows that the initial meniscus curvature can increase up to 76 percent relative to the initial curvature by the electric field before the oil film becomes unstable. The pixel wall and particles are shown to have minimal impact on the interface deformation. • Deformation by an electric field of a confined liquid-liquid interface is modeled. • The meniscus curvature can be increased up to 76% by the applied electric field. • The curvature was quantified by tracking the position of interfacially adsorbed particles. • Fringe fields and colloidal particles have no significant impact on global curvature. [ABSTRACT FROM AUTHOR]

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.

Nanoscale science is becoming increasingly important and prominent, and further development will necessitate integration with other material chemistries. In other words, it involves the construction of a methodology to build up materials based on nanoscale knowledge. This is also the beginning of the concept of post-nanotechnology. This role belongs to nanoarchitectonics, which has been rapidly developing in recent years. However, the scope of application of nanoarchitectonics is wide, and it is somewhat difficult to compile everything. Therefore, this review article will introduce the concepts of liquid and interface, which are the keywords for the organization of functional material systems in biological systems. The target interfaces are liquid–liquid interface, liquid–solid interface, and so on. Recent examples are summarized under the categories of molecular assembly, metal-organic framework and covalent organic framework, and living cell. In addition, the latest research on the liquid interfacial nanoarchitectonics of organic semiconductor film is also discussed. The final conclusive section summarizes these features and discusses the necessary components for the development of liquid interfacial nanoarchitectonics.

Surface enhanced Raman spectroscopy (SERS) is a unique analytical technique with excellent performance in terms of sensitivity, non-destructive detection and resolution. However, due to the randomness and poor repeatability of hot spot distribution, SERS quantitative analysis is still challenging. Meanwhile, snus is a type of tobacco product that can release nicotine and other components in the mouth without burning, and the rapid detection technique based on SERS can reliably evaluate the amount of nicotine released from snus, which is of great significance for understanding its characteristics and regulating its components. Herein, the strategy was proposed to solve the feasibility of SERS quantitative detection based on self-assembled core-shell nanoparticles with embedded internal standards (EIS) due to EIS signal can effectively correct SERS signal fluctuations caused by different aggregation states and measurement conditions, thus allowing reliable quantitative SERS analysis of targets with different surface affinity. By means of process control, after the Au nanoparticles (Au NPs) were modified with 4-Mercaptobenzonitrile (4-MBN) as internal standard molecules, Ag shell with a certain thickness was grown on the surface of the AuNP@4-MBN, and then the Au@4-MBN@Ag NPs were used to regulate and control the assembly of liquid-liquid interface. The high-density nano-arrays assembled at the liquid-liquid interface ensure high reproducibility as SERS substrates, and which could be used for SERS detection of nicotine released from snus products. In addition, time-mapping research shows that this method can also be used to dynamically monitor the release of nicotine. Moreover, such destruction-free evaluation of the release of nicotine from snus products opens up new perspectives for further research about the impact of nicotinoids-related health programs.

Host–guest molecular recognition at the liquid–liquid interface endows the interface with unique properties, including stimuli-responsiveness and self-regulation, due to the dynamic and reversible nature of non-covalent interactions. Increasing research efforts have been put into the preparation of supramolecular interfacial systems such as films and microcapsules by integrating functional components (e.g., colloidal particles, polymers) at the interface, providing tremendous opportunities in the areas of encapsulation, delivery vehicles, and biphasic reaction systems. In this review, we summarize recent progress in supramolecular interfacial systems assembled by host–guest chemistry, and provide an overview of the fabrication process, functions, and promising applications of the resultant constructs.

The assembly and jamming of magnetic nanoparticles (NPs) at liquid-liquid interfaces is a versatile platform to endow structured liquid droplets with a magnetization, i.e., producing ferromagnetic liquid droplets (FMLDs). Here, we use hydrodynamics experiments to probe how the magnetization of FMLDs and their response to external stimuli can be tuned by chemical, structural, and magnetic means. The remanent magnetization stems from magnetic NPs jammed at the liquid-liquid interface and dispersed NPs magneto-statically coupled to the interface. FMLDs form even at low concentrations of magnetic NPs when mixing nonmagnetic and magnetic NPs, since the underlying magnetic dipole-driven clustering of magnetic NP-surfactants at the interface produces local magnetic properties, similar to those found with pure magnetic NP solutions. While the net magnetization is smaller, such a clustering of NPs may enable structured liquids with heterogeneous surfaces.

Contact electrification (CE) in water has attracted much attention, owing to its potential impacts on the chemical reactions, such as the recent discovery of spontaneous generation of hydrogen peroxide (H2O2) in water microdroplets. However, current studies focus on the CE of bulk water, the measurement of CE between micrometer-size water droplets is a challenge and its mechanism still remains ambiguous. Here, a method for quantifying the amount of charge carried by the water microdroplets produced by ultrasonic atomization is proposed. In the method, the motions of water microdroplets in a uniform electric field are observed and the electrostatic forces on the microdroplets are calculated based on the moving speed of the microdroplets. It is revealed that the charge transfer between water microdroplets is size-dependent. The large microdroplets tend to be positively charged while the small microdroplets tend to receive negative charges, implying that the negative charges transfer from large microdroplets to the small microdroplets during ultrasonic atomization. Further, a theoretical model for microdroplets charging is proposed, in which the curvature-induced surface potential/energy difference is suggested to be responsible for the charge transfer between microdroplets. The findings show that the electric field strength between two microdroplets with opposite charges during separation is strong enough to convert OH- to OH*, providing evidence for the CE-induced spontaneous generation of H2O2 in water microdroplets. [ABSTRACT FROM AUTHOR]

Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid-liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl-LiTFSI-water) and HCl-LiTFSI-water, prototypical salt-salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt-salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries. [ABSTRACT FROM AUTHOR]

The paper is devoted to the experimental study of the dynamics of an interface between two liquids with high viscosity contrast filling a vertical, circular narrow gap rotating about a horizontal axis at a speed modulated by librations. The equilibrium shape and stability of the interphase boundary are considered. In the absence of librations, under the action of the centrifugal force the boundary has an axisymmetric shape. At librations, at certain frequency ratios, the interface loses its axisymmetric position: in the cavity reference frame, it is displaced in the radial direction. It is theoretically shown that the discovered phenomenon is explained by the average action of gravity; the results of experiments and theory are consistent. The experiments reveal that with an increase in the modulation amplitude the circular interface loses stability in a threshold manner: an azimuthally periodic relief, quasi-stationary in the cavity frame, emerges. This is associated with the Kelvin–Helmholtz instability due to tangential oscillations of the less viscous liquid near the interface. A dimensionless parameter that determines the stability of the interface is obtained in the limit of high dimensionless libration frequency. The stability threshold increases with the decrease in the dimensionless frequency. This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: As a highly powerful and sensitive tool, surface enhanced Raman scattering (SERS) has attracted extensive attention in quantification analysis. However, the strong dependence of SERS signal on the detailed local nanostructure makes quantitative SERS analysis suffer from difficulties in controlling the uniformity of nanoscale hot spots and the inefficiency of placing the targeted molecules in prefabricated hot spots. Thus, the development of uniform SERS substrates is becoming an urgent demand to impulse SERS technique for the application in practical systems. The self‐assembly of nanoparticles (NPs) at the liquid‐liquid interface (LLI) provides a molecular sharp and defect‐free focal plane, in which the stable controlling of nanogap sizes and the feasible location of analytes can be virtually guaranteed, leading to greatly enhanced sensitivity and reproducibility of detections. On the other hand, the benefit of liquid/liquid systems allows for either hydrophilic, hydrophobic molecules to be captured and detected individually or simultaneously. Based on these advantages of the new SERS substrate, a variety of self‐assembled NP arrays at the LLI have been developed for multiphase analyte detection. Herein, we review recently developed strategies to induce NPs self‐assembly at the LLI and discuss the latest research progress on sensitive and reliable SERS analysis in practical applications. Finally, some perspectives are highlighted in the further development of the efficient methods to enhance the plasmonic properties and more practical SERS sensors for practical applications. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: As a highly powerful and sensitive tool, surface enhanced Raman scattering (SERS) has attracted extensive attention in quantification analysis. However, the strong dependence of SERS signal on the detailed local nanostructure makes quantitative SERS analysis suffer from difficulties in controlling the uniformity of nanoscale hot spots and the inefficiency of placing the targeted molecules in prefabricated hot spots. Thus, the development of uniform SERS substrates is becoming an urgent demand to impulse SERS technique for the application in practical systems. The self‐assembly of nanoparticles (NPs) at the liquid‐liquid interface (LLI) provides a molecular sharp and defect‐free focal plane, in which the stable controlling of nanogap sizes and the feasible location of analytes can be virtually guaranteed, leading to greatly enhanced sensitivity and reproducibility of detections. On the other hand, the benefit of liquid/liquid systems allows for either hydrophilic, hydrophobic molecules to be captured and detected individually or simultaneously. Based on these advantages of the new SERS substrate, a variety of self‐assembled NP arrays at the LLI have been developed for multiphase analyte detection. Herein, we review recently developed strategies to induce NPs self‐assembly at the LLI and discuss the latest research progress on sensitive and reliable SERS analysis in practical applications. Finally, some perspectives are highlighted in the further development of the efficient methods to enhance the plasmonic properties and more practical SERS sensors for practical applications. [ABSTRACT FROM AUTHOR]

The ability to manipulate a liquid meniscus using electrowetting has many applications. In any electrowetting design, at least two electrodes are required: one forms the field to change the contact angle and the other functions as a ground electrode. The contribution of the ground electrode (GE) to the dynamics of electrowetting has not yet been thoroughly investigated. In this paper, we discovered that with a bare ground electrode, the contact angle of a sessile drop increases instead of decreases when a direct current (DC) voltage varying from zero to the threshold voltage is applied. This phenomenon is opposite to what occurs when the GE is coated with a dielectric, where the contact-angle change follows the Lippmann–Young equation above the threshold voltage of electrowetting. However, this behaviour is not observed with either a dielectric-coated electrode using direct current (DC) or a bare ground electrode using alternating current (AC) voltage electrowetting. This study explains this phenomenon with finite element simulation and theory. From previous research work, the ground electrode configuration is inconsistent. In some studies, the ground electrode is exposed to water; in other studies, the ground electrode is covered with dielectric. This study identified that an exposed ground electrode is not required in electrowetting. Moreover, this research work suggests that for applications where precise control of the contact angle is paramount, a dielectric-coated ground electrode should be used since it prevents the increase in the contact angle when increasing the applied potential from zero to the threshold voltage. This study also identified that contact angle hysteresis is lower with a Cytop-coated ground electrode and DC voltage than with a bare ground electrode using AC or DC voltages. [ABSTRACT FROM AUTHOR]

Aligned arrays of semiconducting carbon nanotubes (s-CNTs) with high homogenous density and orientation are urgently needed for high-performance carbon-based electronics. Herein, a length-controlled approach using combined technologies was developed to regulate the s-CNT length and reduce the length distribution. The impact of different lengths and length distributions was studied during aligned self-assembly on a liquid-liquid confined interface was investigated. The results show that short s-CNTs with a narrow distribution have the best alignment uniformity over the large scale. The optimized and aligned s-CNT array can reach a density as high as 100 CNTs·µm−1 on a 4-inch wafer. The field-effect transistor (FET) performance of these optimized s-CNT arrays was 64% higher than arrays without length-control. This study clarified that rational control of s-CNTs with desired length and length distribution on the aligned self-assembly process within the liquid-liquid confined interface. The results illustrate a solid foundation for the application of emerging carbon-based electronics. [ABSTRACT FROM AUTHOR]

Today, the discussion of droplet-fluid interaction is one of the most challenging topics in multiphase (liquid-liquid) flows. In the present study, the behavior of two edible oils (olive oil and canola oil) droplets during the rising in the static fluid of water and passing through the water-oil interface was experimentally investigated. Droplet diameters were controlled in the range of 3.8 to 5.6 mm. First of all, the range of dimensionless numbers was compared to experimental data from other researchers and validated. The results revealed that the droplet shape is elliptical, and that the Weber number decreases in the range of 1 to 2, as the aspect ratio increases. Furthermore, the droplet residence time at the two-phase interface was measured, and the parameters that affected it were examined. Although the results showed that the residence time did not follow a consistent pattern, the conclusion was not far off. Weber dimensionless number was used to introduce hydrodynamic forces and internal surface tension of the droplets. It was shown that none of the theoretical relationships can accurately or even roughly predict the residence time of the oil droplets. Finally, the Weber number has been proven to be dependent on the droplet terminal velocity. Terminal velocity increases with the Weber number and the equivalent diameter.

Dynamic dilational viscoelasticity is an important physical characteristic of interfacial layers because it influences the dynamics and stability of multiphase systems, such as thin liquid films, foams and emulsions. Dilational viscoelasticity depends on many factors. Less studied, but very important, factors are the solubility of the solution components in two contacting liquids, the simultaneous presence of two solution components within a mixed adsorption layer and the curvature of the interface. In this review, we considered several new developments of previously proposed models, which can be used for the analysis of new experimental data. In the presence of such effects, the behaviour of the dilational viscoelasticity becomes more complicated and requires more parameters for its description. An alternative way is to use phenomenological models, which do not identify the particular relaxation processes but propose a description of the dilational viscoelasticity in general terms. [Display omitted] [ABSTRACT FROM AUTHOR]

Over the last decades, the interface between two immiscible electrolyte solutions (ITIES) attracted considerable attention of the scientific community due to their vast applications, such as extraction, catalysis, partition studies and sensing. The aim of this Review is to highlight the potential of electrochemistry at the ITIES for analytical purposes, focusing on ITIES-based sensors for detection and quantification of chemically and biologically relevant (bio)molecules. We start by addressing the evolution of ITIES in terms of number of publications over the years along with an overview of their main applications (Chapter 1). Then, we provide a general historical perspective about pioneer voltammetric studies at water/oil systems (Chapter 2). After that, we discuss the most impacting improvements on ITIES sensing systems from both perspectives, set-up design (interface stabilization and miniaturization, selection of the organic solvent, etc.) and optimization of experimental conditions to improve selectivity and sensitivity (Chapter 3). In Chapter 4, we discuss the analytical applications of ITIES for electrochemical sensing of several types of analytes, including drugs, pesticides, proteins, among others. Finally, we highlight the present achievements of ITIES as analytical tool and provide future challenges and perspectives for this technology (Chapter 5). [Display omitted] • ITIES can be a valuable tool for electrochemical sensing of several types of analytes. • ITIES can be used for the analysis of non-redox (or not easily redox-active) analytes. • Ion transfer reactions for detection of antibiotics, herbicides, drugs, oligonucleotides, etc. • ITIES approaches operates directly in complex matrices without sample pre-treatment. • Application of ITIES-based sensors for in vivo studies and point-of-care (POC) applications. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) pollution has become a focal point of global concern, as the widespread distribution of MPs in the environment poses a potential threat to ecosystems and human health. Despite surface-enhanced Raman scattering (SERS) being one of the most promising detection techniques, the "coffee ring effect" of MPs and their unique size scale make effective contact with SERS substrates challenging. Here, we propose a novel strategy for MPs detection by constructing a plasmonic metasurface at the liquid-liquid interface (LLI). The fluidic properties of LLI provide more flexibility for the uniform dispersion of MPs and the assembly of plasmonic arrays. MPs are captured and assembled on an atomic-level metasurface in a core-shell structure (AuNPs@MPs), providing abundant "hot spots" and additional volume-enhanced Raman effects. This results in enhanced electromagnetic field around MPs and increased enhancement factors, demonstrating high SERS sensitivity and uniformity. This sensing platform provides a new approach for trace detection of MPs and has been validated in practical matrix. [Display omitted] • Metasurface at liquid-liquid-interface for self-assembly of AuNPs@MPs. • AuNPs@MPs provides efficient contact and additional volume-enhanced Raman effect. • The self-healing nature of the metasurface overcomes the "coffee ring effect" of MPs. [ABSTRACT FROM AUTHOR]

In liquidliquid extraction systems, extractants and extracted complexes may have surface activity, resulting in the formation of a variety of supramolecular assemblies such as vesicles and micelles. The assemblies are limited at microscopic and mesoscopic scales. Researches on interface of extraction also focus on microscopic and mesoscopic scales at present. Recently, our group first reported macroscopic supramolecular assembly(MSA) at the interface of extraction systems. The interface can be studied on macroscopic scales by MSA. The process of MSA in ionic liquids(ILs) based extraction systems also provides a new way to study complex supramolecular interactions between ILs and mediums. This review focused on microscopic, mesoscopic and macroscopic supramolecular assembly in extraction systems. First, the interface properties and the process of ion exchange in extraction were summarized. Next, the structures of mesoscopic supramolecular assemblies were reviewed . Finally, the macroscopic supramolecular assembly(MSA) at the interface of extraction systems and its application on separation were emphatically introduced. The MSA process at the interface enriches the extraction methods. And the Marangoni effect presented at the interface supplies a new approach to provide continuous driving force, which is an important scientific problem in the field of MSA.

In this study, liquid–liquid interfacial protein adsorption was proposed as a means of inactivating soy trypsin inhibitors (TIs, including Kunitz (KTI) and Bowman-Birk inhibitor (BBI)). Hexane-water was first selected as a model system to compare three emulsification methods (hand shaking, rotor–stator and ultrasound mixing). Ultrasound could generate the smallest and least polydisperse emulsion droplets, resulting in highest interfacial adsorption amount of KTI and BBI as well as the highest inactivation percentage of TIs (p

Stabilizing liquid-liquid interfaces, whether between miscible or immiscible liquids, is crucial for a wide range of applications, including energy storage, microreactors, and biomimetic structures. In this study, a versatile approach for stabilizing the water-oil interface is presented using the morphological transitions that occur during the self-assembly of anionic, cationic, and nonionic surfactants mixed with fatty acid oils. The morphological transitions underlying this approach are characterized and extensively studied through small-angle X-ray scattering (SAXS), rheometry, and microscopy techniques. Dissipative particle dynamics (DPD) as a simulation tool is adopted to investigate these morphological transitions both in the equilibrium ternary system as well as in the dynamic condition of the water-oil interface. Such a versatile strategy holds promise for enhancing applications such as liquid-in-liquid 3D printing. Moreover, it has the potential to revolutionize a wide range of fields where stabilizing liquid-liquid interfaces not only offers unprecedented opportunities for fine-tuning nanostructural morphologies but also imparts interesting practical features to the resulting liquid shapes. These features include perfusion capabilities, self-healing, and porosity, which could have significant implications for various industries., (© 2024 Wiley‐VCH GmbH.)

The past decades have witnessed the discovery and rapid development of adaptable, reconfigurable all-liquid systems where, by the interfacial assembly and jamming of nanoparticles (NPs), a liquid-liquid system can be structured, i.e., locked into a highly non-equilibrium spatial arrangement, maintaining all the inherent characteristics of the liquids but having the spatial organization and structural stability of a solid. Due to the nature of the interfacial jamming, external stimuli can be used to re-shape the liquids, imparting a responsiveness and malleability to the constructs. In general, the binding energy of a NP to the interface is small, so that compressive forces associated with the reduction in the interfacial area to minimize energy, are sufficient to expel the NPs from the interface. By generating nanoparticle surfactants (NPSs), where ligands dissolved in one liquid can interfacially interact with NPs dispersed in a second immiscible liquid, the binding energy of the NP is massively increased, enabling an interfacial jamming of the NPSs and an arresting of shape changes. Since the jamming is immune to the nature of the NPs, advantage can be taken of the inherent functionality of the NPs, e.g., catalytic, enzymatic, optical, electronic or magnetic, while chemical functionality, including selective functional group recognition, can be introduced through the ligands comprising the NPSs. NPS assemblies can be realized at the interface between any two immiscible liquids (oil-water, oil-oil, and water-water), underscoring the generality of this concept and the range of potential applications. Here, we review some of the basic principles underlying the formation of NPSs and the structuring of liquids, using examples drawn from work in our laboratories and elsewhere, and we provide a perspective on where challenges and applications of this unique state of matter exist.

The interfacial jamming of nanoparticle surfactants offers the possibility of structuring liquids and fabricating all‐liquid constructs with advanced functionality. However, less attention has been given to structured liquids with multiple responsiveness. Here, we show a novel, yet highly simplified nanoparticle surfactant model, pillar[6]arene (PA[6]) surfactant, by taking advantage of the host–guest interactions between a water‐soluble PA[6] and an oil‐soluble ligand, ferrocenium terminated polystyrene. PA[6] surfactants form rapidly at the oil–water interface, assemble into an elastic film with excellent mechanical strength, and when jammed, offer a "solid‐like" assembly to lock‐in highly nonequilibrium shapes of the liquids. The interfacial assembly/jamming and disassembly/unjamming of PA[6] surfactants can be controlled by chemical redox or competitive guest reagents, endowing the structured liquids with redox or guest‐competitive responsiveness. [ABSTRACT FROM AUTHOR]

Host–guest molecular recognition at the liquid–liquid interface endows the interface with unique properties, including stimuli-responsiveness and self-regulation, due to the dynamic and reversible nature of non-covalent interactions. Increasing research efforts have been put into the preparation of supramolecular interfacial systems such as films and microcapsules by integrating functional components (e.g., colloidal particles, polymers) at the interface, providing tremendous opportunities in the areas of encapsulation, delivery vehicles, and biphasic reaction systems. In this review, we summarize recent progress in supramolecular interfacial systems assembled by host–guest chemistry, and provide an overview of the fabrication process, functions, and promising applications of the resultant constructs.

Surfactant adsorption at liquid-liquid interfaces plays an important role in fossil energy fields such as enhanced oil recovery, and temperature is the main factor causing significant changes in surfactant adsorption at interfaces, thus determining the related interfacial tension. In this work, the effect of temperature on the interfacial structure of the tri-n-butyl phosphate (TBP) saturated water/octane was investigated through molecular dynamics simulations. We found that the lowest point of the interfacial tension curve occurs at 280 K. To explain this phenomenon, the effects of temperature on surfactant adsorption, interfacial stability, hydrogen bond network, and water extraction were focused. 280 K corresponds to the maximum adsorption concentration of surfactants, promoting the formation of the water-bridged TBP dimer adduct, TBP(H 2 O)TBP. These aggregates significantly reduce the connectivity between bridging water and the instantaneous interface, which in turn increases surface fluctuations and creates more protrusions, thus promoting subsequent water extraction processes. These results provide important theoretical clues for studying temperature-dependent surface heterogeneity. The interfacial tension curve showed an anomalous temperature dependency, with the curve reaching its lowest point at 280 K. • TBP-filled Octane/Water system exhibits anomalous temperature dependence. • Temperature-dependent TBP adsorption and interfacial hydrogen-bonding networks explain the reason. • This work provides theoretical clues for understanding temperature-dependent surface heterogeneity. [ABSTRACT FROM AUTHOR]

• Electrokinetic effects induce a sharp velocity decrease at fluid interfaces. • Liquid heights greatly affect flow field distribution and droplet moving velocity. • Droplet dynamic viscosity has a minor effect on its electrokinetic velocity. The electrokinetic effects at fluid interfaces can be utilized for droplet manipulation and separation in water, showing promising applications in areas such as oil-water separation and liquid-liquid extraction. In this study, numerical simulations are employed to investigate the impact of electrokinetic effects at the droplet surface and the horizontal interface between a non-conductive liquid and water on the electrokinetic velocity of a droplet within a microchannel. The findings indicate that as the magnitude of the negative zeta potential intensifies at the horizontal liquid-liquid interface, the flow velocity of non-conductive liquid gradually decreases and reverses direction when the zeta potential of the interface exceeds that of the channel wall. Conversely, the flow velocity of water continues to rise, resulting in an increased droplet movement velocity in water. The study also reveals that a lower water height and a greater non-conductive liquid height lead to faster water flow velocity and, consequently, a swifter droplet movement velocity. Additionally, the dynamic viscosity of the droplet has minimal impact on its electrokinetic velocity. [ABSTRACT FROM AUTHOR]

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real‐time quantification of trace norepinephrine (NE). The rigid molecule, 4‐(thiophen‐3‐ylethynyl)‐benzaldehyde (RP1) was designed and co‐assembled at AuNPs with 4‐mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in‐the‐field testing of NE in rat brain microdialysates following anxiety. [ABSTRACT FROM AUTHOR]

This work presents a novel sensor setup for the general detection of liquid-liquid interfaces in different mixes of liquids as part of a liquid-liquid extraction device. The sensor setup is applied to a laboratory scale separatory funnel. It uses a near infrared sensor array which receives light going through the liquids inside the funnel, which are illuminated by a light source located on the other side and below the funnel. Light refracts inside the funnel and the liquids and reflects on the interface creating changing patterns in the light intensity measured by the sensor, providing a way of locating the liquid-liquid interface. Liquid mixes with different optical features, from transparent to opaque, emulsion and clean, are used to test whether different types of interfaces produce a distinguishable response on the sensor, allowing to detect interfaces in different situations that can occur as part of an Artificial Intelligence orchestrated battery chemical synthesis process. Emulsion interfaces create a discernible change in the sensor input by lowering the light intensity registered when crossing in front of the sensor making them easier to locate than with other optical techniques. The setup opens the possibility of detecting a liquid-liquid interface as it is forming and can be miniaturized to be attached to laboratory funnels as a manual aid or used with other transparent vessels in automatic solutions like liquid handling robots or pipetting robots. [ABSTRACT FROM AUTHOR]

The liquid‐liquid interface (LLI) technique has been used to form thin films of various materials parallel to the interface. In this report, by taking CuS as an example, we show that CuS not only adopts thin film structures at the liquid‐liquid interface parallel to the interface but can also utilize beyond the interface to form self‐supported vertically aligned CuS thin films by controlling the precursor concentration. We also report the formation of a self‐assembled monolayer of CuS nanoparticles in the dichlorobenzene‐water interface at a lower concentration of copper. Thin films generated at LLI show p‐type conductivity with a sheet resistance of ∼350 Ω/□ and transparency up to 72 % at 550 nm. CuS also show electrocatalytic activity towards glucose sensing with a sensitivity of 3958 μA mM−1 cm−2, which is among the best in copper‐based materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Organophosphorus-based ligands represent a versatile set of solvent extraction reagents whose chemical makeup plays an important role in extraction mechanism. We hypothesize that the branching of the extractant hydrophobic tail and its oil-phase solvation affect the liquid/liquid interfacial structure. Understanding the structure mediated adsorption and interfacial ordering becomes key in designing ligands with enhanced selectivity and efficiency for targeted extractions. We employed vibrational sum frequency generation spectroscopy and interfacial tension measurements to extract thermodynamic adsorption energies, map interfacial ordering, and rationalize disparate behaviors of model di-(2-ethylhexyl) phosphoric acid and dioctyl phosphoric acid ligands at the hexadecane water interface. With increased surface loading, ligands with branched hydrophobic tails formed stable interfaces at much lower concentrations than those observed for ligands with linear alkyl tails. The lack of an oil phase and associated solvation results in markedly different interfacial properties, and thus measurements made at air/liquid surfaces cannot be assumed to correlate with the processes occurring at buried liquid/liquid interfaces. We attribute these differences in the surface mediated self-assembly to key variations in hydrophobic interactions and tail solvation taking place in the oil phase demonstrating that interactions in both the polar and nonpolar phases are essential to understand self-assembly and function. [ABSTRACT FROM AUTHOR]

[Display omitted] For conventional high internal phase emulsions (HIPEs) with an external osmotic pressure greater than Laplace pressure, once the osmotic balance is broken, the swelling or shrinking of the aqueous phase can easily trigger phase separation. Mixing two immiscible dispersed phases in a double HIPE can evolve differently following an osmotic shock, which is expected to create a synergistic effect that can frustrate the phase separation of the system. Osmotic responses of double HIPEs were studied at the surface of a NaCl solution at a range of molarities. Fluorescence confocal microscopy studies were carried out to track the responses on microscopic scales. Measurements on surface tensions revealed the interfacial behaviors of the used surfactant. A synergistic effect is achieved by a symbiotic process between the dispersed oils, where one type of droplets become more stable and pack around the other ones to halt their coalescence. The essential drive comes from the adsorption/desorption of surfactant molecules at oil–water interfaces. By directly adjusting the osmotic pressure difference, transitions between osmotic down-shock and osmotic up-shock can also be realized. This symbiosis greatly expands the potential technological applications of multiple-liquid systems, and can be used to design novel multi-functional composite materials. [ABSTRACT FROM AUTHOR]

Liquid–liquid interfaces of liquid alloys with electrolytic solutions present fertile platforms for realizing exciting interfacial phenomena that can be devised to process alloys and produce nanomaterials. Here, such an interface is established by immersing a gallium–bismuth binary liquid alloy into aqueous electrolytes. It is shown that the application of a negative voltage to this interface results in a rapid and complete liberation of bismuth nanostructures from liquid gallium. The set of conditions that govern the chemistry of the interface can be adjusted to control the oxidation state, morphology, and crystal structure of the expelled bismuth. By changing the conditions; nanotubular, atomically thin plates, and sea‐urchin‐shaped bismuth oxide morphologies are obtained. The process can also control the crystal phase of bismuth oxide as monoclinic (α), tetragonal (β), or body‐centered cubic (γ). The addition of ascorbic acid to the electrolyte is observed to prevent the oxidation of the expelled entities, resulting in bismuth metal nanoparticles. Ab initio molecular dynamics and computational fluid dynamics simulations are performed to elucidate this rapid phase separation at the interface. This knowledge will potentially lead to new pathways for using alloys as reaction media to refine metals while simultaneously producing nanomaterials for various applications. [ABSTRACT FROM AUTHOR]

Knowledge of interfacial structures in liquid–liquid systems is imperative, especially for improving two-phase biological and chemical reactions. Therefore, we developed a new sample cell for neutron reflectometry (NR), which enables us to observe the layer structure around the interface, and investigated the adsorption behavior of a typical surfactant, sodium dodecyl sulfate (SDS), on the toluene-d8-D2O interface under the new experimental conditions. The new cell was characterized by placing the PTFE frame at the bottom to produce a smooth interface and downsized compared to the conventional cell. The obtained NR profiles were readily analyzable and we determined a slight difference in the SDS adsorption layer structure at the interface between the toluene-d8-D2O and air-D2O systems. This could be owing to the difference in the adsorption behavior of the SDS molecules depending on the interfacial conditions. [ABSTRACT FROM AUTHOR]

The passage of a rising air bubble through a stratified horizontal interface between two Newtonian liquids is studied numerically. A ternary phase‐field model has been utilized for capturing the interface between three immiscible fluids. According to the previous studies, the density, viscosity, and surface tension of the two liquids, in addition to the bubble diameter, are the effective parameters of bubble interaction with the interface. By changing these variables, three main flow patterns are identified in numerical simulations. Penetration flow regime is observed when the bubble enters the upper liquid alone and does not raise the lower liquid. Entrainment flow regime occurs when the bubble lifts some of the heavier liquid to the lighter liquid but still rises alone. If the bubble holds a film of the denser liquid when it rises in the upper liquid, envelopment flow regime takes place. A flow regime map is represented to distinguish the aforementioned flow patterns using Weber and Morton numbers and determine regime transition criteria based on these two dimensionless parameters. For Weber numbers lower than 30, or Morton numbers higher than 1.7 × 10−2, the penetration regime is observed. On the contrary, when the Weber number is higher than 65 and the Morton number is lower than 7 × 10−5, the envelopment regime occurs. The entrainment pattern happens between these ranges and two additional limiting relations of 320Mo0.18 < We < 1500Mo0.23. [ABSTRACT FROM AUTHOR]

Advanced functional materials require sophisticated control of particle characteristics. The bottom-up process has been extensively used to produce functional materials for controlling the particle properties of composite particles. We propose crystallization at liquid-liquid interfaces as an advanced particle formation method. This review introduces crystallization at a liquid-liquid interface based on several case studies used in various applications. Conventional crystallization has been generally used to produce crystals and particles with homogeneous particle properties. Liquid-liquid interfacial crystallization makes it possible to create composite particles with hetero-phase structures and interfaces. Liquid-liquid interfacial crystallization with an inkjet technique can control the droplet size accurately, and the shape and particle size distribution are successfully controlled in inorganic-organic composite particles. In addition, we succeed in creating organic-organic composite particles using the interfacial crystallization by an ultrasonic spray nozzle. The coating efficiency of organic particles on the particles is enhanced using the ultrasonic spray nozzle in comparison with anti-solvent crystallization. In this study, the fabrication of inorganic-organic composite particles using a coaxial tube reactor on the liquid-liquid interfacial crystallization is proven successful. These findings suggest that liquid-liquid interfacial crystallization is a promising means of efficiently producing composite particles because of their applicability to infusion in various processes.

Lithium-ion battery (LiB) waste powder is a valuable source of various materials, including carbon and metals. Although this material exhibits electrical conductivity, nanostructured morphology, and may contain metal oxides, it has not been used as an electrocatalyst. Here, we demonstrated the application of LiB waste powder as a catalyst for electrochemical H2O2 generation. The powder was both immobilized on a glassy carbon (GC) electrode and assembled at a liquid–liquid interface formed by decamethylferrocene (DMFc) solution in trifluorotoluene and aqueous perchloric acid in the presence of oxygen. The electrochemistry was studied by cyclic voltammetry and also with a rotating disk electrode (RDE), and a 2-electron ORR pathway was confirmed. H2O2 generation at the liquid–liquid interface and oxidation of DMFc were detected by colorimetry, UV–vis spectroscopy and scanning electrochemical microscopy (SECM). The use of LiB waste powder reduces the ORR onset potential by ca. 0.3 V compared to an unmodified GC. When assembled at a liquid–liquid interface the waste powder increases the efficiency of H2O2 generation by ca. 20 times.