On the Investigation of the Droplet–Droplet Interactions of Sodium 1,4‐Bis(2‐ethylhexyl) Sulfosuccinate Reverse Micelles upon Changing the External Solvent Composition and Their Impact on Gold Nanoparticle Synthesis

Abstract

The effect of the composition of the nonpolar organic media on the properties of sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles (RMs) at a fixed temperature were investigated. To monitor interfacial micropolarity and sequestrated water structure in n-heptane:benzene/AOT/ water RMs, the solvatochromic behavior of coumarin 343 (C343) as an absorption and emission probe was studied, and the size of the droplets was measured by dynamic light scattering (DLS). The DLS results confirm the formation of the nheptane:benzene/AOT/water RMs at every n-heptane mole fraction investigated. The data show that as the n-heptane content increases, the interdroplet attractive interactions and the droplet size both increase. With C343 spectroscopy, we determined the "operational" critical micellar concentration, the interfacial micropolarity of the RMs, the hydrogen-bond ability of the media, and the sequestrated water structure in every RM system studied. To verify the modulation of the interdroplet interactions by the external solvent, we have used a well-known synthetic method to create gold nanopar-

Nonpolar Interface Composition in Cetyltrimethylammonium Bromide Reverse Micellar Environments to Control Size and Induce Anisotropy on Gold Nanoparticles

“…It was evidenced by 1 H NMR spectroscopy as an upfield shift of the protons of the surfactant head group given its deficient penetration into the polar core. Similar spherical and highly monodispersed AuNPs were found in n ‐heptane/AOT/water RMs by Gutierrez et al . They reported a fast nucleation process according to the fact that the droplet–droplet interactions are favored and the rate of material exchange among the micelles is increased in these RMs.…”

“…It is because of the attractive interaction between droplets increased, favoring interdroplet interactions and leading to a higher tendency to aggregate and also results in more stable RMs . Moreover, this fact could be correlated with the surfactant packing and, therefore, have an effect on the RMs droplet sizes, as observed above …”

Micropolarity and Hydrogen‐Bond Donor Ability of Environmentally Friendly Anionic Reverse Micelles Explored by UV/Vis Absorption of a Molecular Probe and FTIR Spectroscopy

“…Interestingly, we observed similarities between these biocompatible solvents and those traditionally used to create RMs such as n ‐heptane and benzene. In this sense, the W 0 max values observed in ML/AOT and n ‐heptane/AOT were quite similar and, for IPM/AOT and benzene/AOT only slightly different but both are able to dissolve less water than ML/AOT or n ‐heptane/AOT RMs . Additionally, the similar N agg values obtained for IPM/AOT/water and benzene/AOT/water, around 30, and for ML/AOT/water and n ‐heptane/AOT/water around 180 reinforces the idea that IPM and ML have analogous behavior in AOT RMs that benzene and n ‐heptane, respectively.…”

“…Reverse micelles (RMs) are a class of self‐assemblies system generally described as nanometer sized water droplets dispersed in a nonpolar solvent with the aid of a surfactant monolayer . Polar and nonpolar substances can be solubilized by RMs and this ability confer to them several applications in fields such as chemical and enzymatic reactions, nanomaterials synthesis, in drug delivery systems, among others. Different kinds of surfactants (anionic, cationic and nonionic) have been used to formulate RMs in nonpolar solvents.…”

The Use of AOBH‐DEHP Molecular Probe to Characterize BHDC Reverse Micelles Interfaces. Insights on the Interfacial Water Structure

“…They are thermodynamically stable aggregates that exist as a transparent phase dispersed in a non‐polar solvent, in which the polar head groups of the amphiphilic molecules, the surfactants, point inward and the hydrocarbon chains point toward to the non‐polar medium Many studies have investigated their physicochemical properties and, they are widely used for different purposes such as nanoparticles formation, enzymatic reaction,‐ charge transfer processes purification/extraction of biomolecules,‐ models for biological membranes and many others …”