Electrostatic interactions to modulate the reflective assembly of nanoparticles at the oil–water interface

Luo, Mingxiang; Olivier, Gloria K.; Fréchette, Joëlle

doi:10.1039/c2sm26890f

Cited by 46 publications

(66 citation statements)

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“…Ligand-grafted metal or semiconductor nanocrystals at fluid-fluid interfaces are widely used in nanomaterials synthesis [13][14][15] and in catalytic processes [16]. Simulation studies predict the rearrangement of the ligand brush into anisotropic lensshaped configurations when these nanoparticles adsorb at fluid-fluid interfaces [4][5][6]8].…”

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confidence: 99%

“…Our measurements also confirm the importance of surface-active trace ligands in the behavior of nanoparticleladen fluid-fluid interfaces. The equilibrium behavior and mechanical response of nanoparticle monolayers have important consequences in many emerging applications that exploit nanoparticles at fluid-fluid interfaces, for instance, in the making of 2D nanomaterials with tunable optical properties [13,14] where precise control of interactions and stability is crucial for obtaining reversible properties. Our experimental method for the measurement of interactions between nanocolloids at fluid interfaces makes it possible to validate simulation studies not only of the mean-field interaction potential between ligand-coated nanoparticles [9] but also of the effect of 2D confinement on the interaction potential between star polymers [28] and other soft nanoparticles.…”

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Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces

et al. 2015

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Nanoparticles with grafted layers of ligand molecules behave as soft colloids when they adsorb at fluidfluid interfaces. The ligand brush can deform and reconfigure, adopting a lens-shaped configuration at the interface. This behavior strongly affects the interactions between soft nanoparticles at fluid-fluid interfaces, which have proven challenging to probe experimentally. We measure the surface pressure for a stable 2D interfacial suspension of nanoparticles grafted with ligands, and extract the interaction potential from these data by comparison to Brownian dynamics simulations. A soft repulsive potential with an exponential form accurately reproduces the measured surface pressure data. A more realistic interaction potential model is also fitted to the data to provide insights into the ligand configuration at the interface. The stress of the 2D interfacial suspension upon step compression exhibits a single relaxation time scale, which is also attributable to ligand reconfiguration.

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Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces

et al. 2015

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“…Besides, ions have a strong interaction with molecules coupled with charged groups (such as ionic surfactants and asphaltene), changing the diffusion behavior and interfacial molecular packing of these species, [15][16][17][18] which would lead to special interfacial mechanics.…”

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confidence: 99%

Ionic hydration-induced evolution of decane–water interfacial tension

Wen

Sun

Bai

et al. 2017

Phys. Chem. Chem. Phys.

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bcBuilding a connection between the variations in interfacial tension and the microstructure of the oil-water interface is still very challenging. Here, we employ a molecular dynamics method to study the effect of monovalent ions on the decane-water interfacial tension and reveal the relationship between ionic hydration and the variation of interfacial tension. Our results indicate that interfacial tension presents a non-monotonic dependence on the ionic concentrations owing to the distinctive adsorption characteristics of ions. At low ionic concentrations, the hydration of the discrete ions at the interface causes an enhancement in the virial term of the interfacial tension, resulting in an increase of the interfacial tension with increasing ionic concentrations. At high ionic concentrations, the ion pairs at the interface weaken the ionic hydration, thus the virial term of the interfacial tension decreases and the interfacial tension decreases slightly. In addition, the kinetic energy term of interfacial tension increases only with increasing temperature, while the virial term decreases with an increase in either temperature or pressure on account of the weakening ionic hydration; therefore, the increase of temperature and pressure induces different degrees of the decrease in the interfacial tension owing to the major contribution of the virial term, particularly at high ionic concentrations.

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“…Desorption has been obtained for instance by the addition of a surface-active agent (10,11). In addition, by tuning the strength of electrostatic repulsion between charged particles at an interface through pH and electrolyte concentration, the surface density of particles can be shifted to very low values up to complete removal (12,13). We propose to develop particle removal methods that eliminate the need for physicochemical modifications.…”

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Ultrafast desorption of colloidal particles from fluid interfaces

Poulichet

Garbin

2015

Proc. Natl. Acad. Sci. U.S.A.

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The self-assembly of solid particles at fluid-fluid interfaces is widely exploited to stabilize emulsions and foams, and in materials synthesis. The self-assembly mechanism is very robust owing to the large capillary energy associated with particle adsorption, of the order of millions of times the thermal energy for micrometer-sized colloids. The microstructure of the interfacial colloid monolayer can also favor stability, for instance in the case of particle-stabilized bubbles, which can be indefinitely stable against dissolution due to jamming of the colloid monolayer. As a result, significant challenges arise when destabilization and particle removal are a requirement. Here we demonstrate ultrafast desorption of colloid monolayers from the interface of particle-stabilized bubbles. We drive the bubbles into periodic compression-expansion using ultrasound waves, causing significant deformation and microstructural changes in the particle monolayer. Using high-speed microscopy we uncover different particle expulsion scenarios depending on the mode of bubble deformation, including highly directional patterns of particle release during shape oscillations. Complete removal of colloid monolayers from bubbles is achieved in under a millisecond. Our method should find a broad range of applications, from nanoparticle recycling in sustainable processes to programmable particle delivery in lab-on-achip applications.self-assembly | colloidal interactions | Pickering | interfacial assemblies C olloidal particles can adsorb to fluid-fluid interfaces and confer outstanding stability to emulsions and foams (1, 2). The interfacial self-assembly of colloids has been used to create novel materials, for instance colloidosomes (3) and bijels (4). These applications rely on the large decrease in free energy accompanying particle adsorption, ΔE = −γ 0 πa 2 ð1 − cos θÞ 2 , which depends on the surface tension γ 0 , the particle size a, and the three-phase contact angle θ (5), and ranges from hundreds to millions of times the thermal energy for nanometer-to micrometer-sized particles. The microstructure that the colloidal particles form at the interface has also been shown to enhance stability. For instance, jamming of an interfacial colloid monolayer prevents coarsening in bicontinuous emulsions (4) and can arrest the dissolution of particle-stabilized bubbles (6). Particle removal from fluid-fluid interfaces is a significant challenge in emerging applications of functional nanoparticles in interfacial biocatalysis (7), gas storage (8), and biomass conversion (9), where the ability to recover and regenerate the nanoparticles at the end of the process is a key requirement. The most common approaches to particle removal from fluid interfaces are based on the physicochemical modification of the fluid phases or the interface. Desorption has been obtained for instance by the addition of a surface-active agent (10, 11). In addition, by tuning the strength of electrostatic repulsion between charged particles at an interface through pH and el...

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Electrostatic interactions to modulate the reflective assembly of nanoparticles at the oil–water interface

Cited by 46 publications

References 59 publications

Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces

Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces

Ionic hydration-induced evolution of decane–water interfacial tension

Ultrafast desorption of colloidal particles from fluid interfaces

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