Aqueous foams and emulsions stabilized by mixtures of silica nanoparticles and surfactants: A state-of-the-art review

Briceño-Ahumada, Zenaida; Soltero-Martínez, J. Félix Armando; Castillo, René Jiménez

doi:10.1016/j.ceja.2021.100116

Cited by 46 publications

(16 citation statements)

References 180 publications

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“…We selected SiO 2 nanoparticles and C n TAB surfactants as model components for our studies for several reasons. First, SiO 2 /C n TAB complexes have been used in previous studies to stabilize a broad range of conventional, isotropic oil-in-water emulsions. ,,,,− SiO 2 nanoparticles alone do not generally accumulate at oil–water interfaces because they are hydrophilic. , However, because they are negatively charged, combining them with cationic surfactants can increase hydrophobicity and thus promote adsorption. ,,, Second, as opposed to emulsions formed by SiO 2 (or other) nanoparticles alone, this mixed nanoparticle–surfactant system also provides opportunities to vary composition and surfactant structure (e.g., tail length) in ways that have the potential to impact both the colloidal stability and the sensitivity of the response of the LC droplets to added analytes. This hypothesis is based on observations in past studies showing (i) that the adsorption of SiO 2 /C n TAB complexes to air–water interfaces depends upon surfactant tail length, with the magnitude of surface tension decreasing monotonically with increasing surfactant tail length, and (ii) that the orientation of LCs in thin films or emulsion droplets ,, is strongly influenced by the structures of the tails of surfactants that adsorb from aqueous solution, with longer tails generally leading to orientational transitions at lower bulk surfactant concentrations. , Finally, we reasoned that a stabilizing system based on a formulation using cationic surfactants would provide opportunities to decorate LC droplet surfaces with particles that have the potential to permit discrimination among other charged amphiphiles, providing a possible means to further modulate response and introduce selectivity into these systems.…”

Section: Resultsmentioning

confidence: 99%

Environmentally Responsive Emulsions of Thermotropic Liquid Crystals with Exceptional Long-Term Stability and Enhanced Sensitivity to Aqueous Amphiphiles

2022

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We report colloidally stable emulsions of thermotropic liquid crystals (LCs) that can detect the presence of amphiphilic analytes in aqueous environments. Our approach makes use of a Pickering stabilization strategy consisting of surfactant–nanoparticle complexes (SiO2/C n TAB, n = 8, 12, 16) that adsorb to aqueous/LC droplet interfaces. This strategy can stabilize LC emulsions against coalescence for at least 3 months. These stabilized LC emulsions also retain the ability to respond to the presence of model anionic, cationic, and nonionic amphiphiles (e.g., SDS, C12TAB, C12E4) in aqueous solutions by undergoing “bipolar-to-radial” changes in LC droplet configurations that can be readily observed and quantified using polarized light microscopy. Our results reveal these ordering transitions to depend upon the length of the hydrocarbon tail of the C n TAB surfactant used to form the stabilizing complexes. In general, increasing C n TAB surfactant tail length leads to droplets that respond at lower analyte concentrations, demonstrating that this Pickering stabilization strategy can be used to tune the sensitivities of the stabilized LC droplets. Finally, we demonstrate that these colloidally stable LC droplets can report the presence of rhamnolipid, a biosurfactant produced by the bacterial pathogen Pseudomonas aeruginosa. Overall, our results demonstrate that this Pickering stabilization strategy provides a useful tool for the design of LC droplet-based sensors with substantially improved colloidal stability and new strategies to tune their sensitivities. These advances could increase the potential practical utility of these responsive soft materials as platforms for the detection and reporting of chemical and biological analytes.

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Section: Resultsmentioning

confidence: 99%

Environmentally Responsive Emulsions of Thermotropic Liquid Crystals with Exceptional Long-Term Stability and Enhanced Sensitivity to Aqueous Amphiphiles

2022

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“…This is because when the surfactant concentration is high, most of the SiO 2 nanoparticles have a dense double adsorption layer on their surface, which restores strong hydrophilicity so that the particles cannot be stably adsorbed on the gas–liquid interface. At this time, the stability of the C 12 A-N20 foam is almost the same as that of the C 12 A foam ( Briceño-Ahumada et al., 2021 ).…”

Section: Resultsmentioning

confidence: 76%

Synthesis and stability of switchable CO2-responsive foaming coupled with nanoparticles

et al. 2022

iScience

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“…Oil−water emulsification and emulsions are extensively applied in many technical fields, such as medicine, cosmetics, food, chemicals, petroleum industry, and so on. 1,2 As reported in the oil field, more than two-thirds of crude oil is produced in the emulsion form. 3 Especially in the enhanced oil recovery (EOR) stage of crude oil production, emulsification has been demonstrated as an important mechanism to extend the lifetime of oil fields.…”

Section: Introductionmentioning

confidence: 93%

A Novel Method to Characterize Dynamic Emulsions Generation and Separation of Crude Oil–Water System

Yue

Zou

et al. 2022

Ind. Eng. Chem. Res.

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The evaluation of the ease to generate emulsions and emulsions stability of oil−water system is essential for the investigation and application of chemical flooding technology for the enhanced oil recovery (EOR). However, the previous characterization methods have mainly focused on emulsion stability. To fill this gap, this study designed a novel instrument for visualizing the presence of emulsions and the separation of an oil−water system. Thereafter it also proposed quantitative methods: the emulsification index (EI) for characterizing the ease of surfactants to generate emulsions with crude oil and the demulsification index (DI) for describing emulsion stability. The results show that EI and DI can accurately characterize the dynamic characteristics of emulsions generation and demulsification, respectively. On the basis of the numerous test data composed by three crude oils and seven surfactants with different concentrations, the emulsifying capability and emulsion stability of different oil−water samples can be quantitatively determined. More importantly, these differences between various oil−water samples caused by surfactant concentration, surfactant types and crude oil property can also be accurately distinguished. Besides, the core flooding tests also provide support for the EI and DI and are reasonable parameters for characterization of the emulsification capability and emulsion stability of oil−water systems. Therefore, the overall investigations ultimately revealed that the parameters EI and DI can be used to determine ease of emulsion generation and separation of oil−water systems with an acceptable level of accuracy. The findings of this study provide a novel method for preparing effective chemical agents, which is useful for EOR fields with economic returns.

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Aqueous foams and emulsions stabilized by mixtures of silica nanoparticles and surfactants: A state-of-the-art review

Cited by 46 publications

References 180 publications

Environmentally Responsive Emulsions of Thermotropic Liquid Crystals with Exceptional Long-Term Stability and Enhanced Sensitivity to Aqueous Amphiphiles

Environmentally Responsive Emulsions of Thermotropic Liquid Crystals with Exceptional Long-Term Stability and Enhanced Sensitivity to Aqueous Amphiphiles

Synthesis and stability of switchable CO2-responsive foaming coupled with nanoparticles

A Novel Method to Characterize Dynamic Emulsions Generation and Separation of Crude Oil–Water System

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