Tracking of Nanoparticle Diffusion at a Liquid–Liquid Interface Adsorbed by Nonionic Surfactants

Abstract

Emulsions stabilized by both nanoparticles and surfactants often display longer shelf life than those stabilized by nanoparticles or surfactants alone. Although numerous works have been conducted to understand the effect of nanoparticles and surfactants on the variation of interfacial tension, little is known about interfacial diffusion when both nanoparticles and surfactants are present at interfaces. In this work, we used single-particle fluorescence tracking to study the lateral diffusion of individual hydrophobic nanoparticles at hexane−glycerol interfaces adsorbed by different amounts of nonionic surfactants. When the surfactant concentration is over a threshold, we found that the nanoparticle diffusion exhibits a two-regime behavior involving short-time Brownian and the emergence of subdiffusive, non-Gaussian, and dynamically anticorrelated diffusion in the long lag time regime. A stepwise analysis rationalized diffusion in different lag time regimes, leading to a mechanistic interpretation regarding the two-regime behavior. These results could provide insight into the understanding of the synergistic effect for the surfactant-assistant Pickering emulsion.

Interfacial Nucleation Mechanism of Water-Soluble Ag–In–S Quantum Dots at Room Temperature and Their Visible Light Catalytic Performance

“…When the pH value continued to rise, the photocatalytic degradation reaction was basically not carried out. This indicates that the interfacial reaction between the sulfur source and the cation is seriously hindered by the hydroxide ions outside the complex . A similar situation occurred in the photocatalytic experiment of AgInS 2 QDs prepared by using CA as the ligand and adjusting the pH value of CA.…”

“…This indicates that the interfacial reaction between the sulfur source and the cation is seriously hindered by the hydroxide ions outside the complex. 62 A similar situation occurred in the photocatalytic experiment of AgInS 2 QDs prepared by using CA as the ligand and adjusting the pH value of CA. When the pH value of the solution was greater than 5, the photocatalytic degradation rate of methyl orange decreased dramatically (Figure S7).…”

Protein Desorption Kinetics Depends on the Timescale of Observation

“…To address this concern, a bottom-up approach using single-molecule tracking methods was proposed because it enables the direct, model-free quantification of distinct microscopic processes such as adsorption, surface diffusion, and desorption of fluorescently labeled molecules at liquid–liquid and solid–liquid interfaces under steady-state conditions. − However, kinetic parameters acquired in such experiments, such as the adsorption and desorption rate constants k a and k d , are sensitive to the characteristic timescales of the experiments. For example, the k d of bovine serum albumin (BSA) on a fused silica surface is measured to be approximately 0.3 s –1 when using single-molecule tracking with an image acquisition time t ac = 0.1 s. Comparatively, an early single-molecule study with relatively low temporal resolution analyzed total BSA coverage as a function of time with a Langmuir model and found k d = 0.02 s –1 . , An important question arising from this apparent inconsistency is whether the timescale on which desorption is observed influences the apparent characteristic residence time that will be obtained.…”

Single-Molecule Tracking of Reagent Diffusion during Chemical Reactions

“…This makes SMT very suitable for acquiring the precise value of D in different timescales . The SMT enabled the scientists to understand details about, for example, the polymerization, the molecular movement in cells, − and dynamics in complex environments, − at the plasma membranes, − and on solid–liquid − and liquid–liquid , interfaces. Because SMT is essentially an imaging method, this technique can circumvent the inconsistent signal fitting and interpretation ,, and rule out concerns in which photophysical artifacts , and bulk fluid convection were erroneously interpreted as the variation of D .…”