Properties of Fatty Amine–Silica Nanoparticle Interfacial Layers at the Hexane–Water Interface (original) (raw)
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2021
Fundamental insights into the interplay and self-assembly of nanoparticles and surface-active agents at the liquid-liquid interface play a pivotal role in understanding the ubiquitous colloidal systems present in our natural surroundings, including foods and aquatic life, and in the industry for emulsion stabilization, drug delivery, or enhanced oil recovery. Moreover, well-controlled model systems for mixed interfacial adsorption of nanoparticles and surfactants allow unprecedented insights into nonideal or contaminated particle-stabilized emulsions. Here, we investigate such a model system composed of hydrophilic, negatively, and positively charged silica nanoparticles and the oil-soluble cationic lipid octadecyl amine with in situ synchrotron-based X-ray reflectometry, which is analyzed and discussed jointly with dynamic interfacial tensiometry. Our results indicate that negatively charged silica nanoparticles only adsorb if the oil-water interface is covered with the positively ...
Journal of Colloid and Interface Science, 2019
There is a notable paucity of studies investigating the impact of charged nanoparticles on the interfacial behavior of nonionic surfactants, assuming that the interactions are negligible in the absence of electrostatic forces. Here, we argue about our observations and the existence of a complex interfacial behavior in such systems depending on the type and chemical structure of surfactant. This study set out to investigate the effects of interactions between hydrophilic silica nanoparticles (NP) and non-ionic surfactants on water/heptane dynamic interfacial properties using drop profile analysis tensiometry (PAT). Three surfactants were studied, namely Triton X-100 (significantly soluble in water phase), C 12 DMPO (well soluble in both phases) and SPAN 80 (oil-soluble). The different chemical structures and partition coefficients of the surfactants enabled us to cover possible interactions and differentiate between bulk and interfacial interactions. We observed that hydrophilic silica NPs had a negligible effect on the interfacial behavior of Triton X-100, that they increased the surface activity of C 12 DMPO when both compounds are initially in the aqueous phase. Most interestingly is that the added NPs generated unstable interfacial NP-surfactant complexes and reduced the pseudo-equilibrium interfacial tension of oil-soluble surfactant, Span 80, even though NPs and surfactants were in different bulk phases.
Journal of Petroleum Science and Engineering, 2020
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Energy & Fuels, 2018
Efficient phase separation of oil and water in emulsions is critical for water treatment processes and hydrocarbon processing. Our research aims at elucidating the separation of water-in-oil emulsions using silica nanoparticles (SNP's). By probing the surfactantnanoparticle interactions, we showed that surfactant stabilized emulsions can be destabilized depending on the nanoparticle wettability and the mode of nanoparticle addition. The efficiency of nanoparticles to demulsify surfactant stabilized emulsions depended on both the nanoparticle and surfactant concentration. Water-in-oil emulsions were destabilized when partially hydrophobic nanoparticles were added to the surfactantstabilized emulsion after emulsion formation (post-mixing). Hydrophilic and partially hydrophobic nanoparticles adsorb the surfactants via hydrogen bonding that in turn leads to depletion of surfactants at the oil-water interface. Upon the addition of hydrophilic nanoparticles, the preferential distribution of nanoparticles in the water phase led to lower adsorption of surfactants from the oil phase resulting in inefficient destabilization as compared to partially hydrophobic nanoparticles. Water-in-oil emulsions were not destabilized upon post-mixing hydrophobic nanoparticles due to weak hydrophobic interactions between surfactants and hydrophobic nanoparticles. For a fixed concentration of nanoparticles of specific wettability, changing the mode of nanoparticle addition
Silica Nanoparticle Wettability: Characterization and Effects on the Emulsion Properties
Industrial & Engineering Chemistry Research, 2015
Recent interest in the use of nanoparticles in emulsion stabilization has driven increased efforts to understand how the characteristics of the particles influence emulsion properties. While it is clear that contact angle and wettability must play significant roles in determining the type of emulsion formed, it is not straightforward to measure the contact angle of a nanoparticle. In this paper we compare multiple techniques for characterizing the water-air contact angle of silica nanoparticles while systematically varying the hydrophobicity of the nanoparticles using silanization. We then compare the performance of the particles in decane/water emulsions. While the heat of immersion measured by microcalorimetry is found to provide the best method for discriminating between the wettability of the particles, the fraction of surface covered by the silane groups was observed to affect the structure of the emulsion more profoundly than the differences in the contact angles of the particles. Furthermore, we find that the phase of initial dispersion is extremely influential in determining the resulting emultion type and droplet size.
Silica Nanoparticle Wettability: Characterization and Effects on Emulsion Properties
Recent interest in the use of nanoparticles in emulsion stabilization has driven increased efforts to understand how 7 the characteristics of the particles influence the emulsion properties. While it is clear that the contact angle and wettability must 8 play significant roles in determining the type of emulsion formed, it is not straightforward to measure the contact angle of a 9 nanoparticle. In this paper, we compare multiple techniques for characterizing the water−air contact angle of silica nanoparticles 10 while systematically varying the hydrophobicity of the nanoparticles using silanization. We then compare the performance of the 11 particles in decane/water emulsions. While the heat of immersion measured by microcalorimetry is found to provide the best 12 method for discriminating between the wettability of the particles, the fraction of surface covered by the silane groups was 13 observed to affect the structure of the emulsion more profoundly than the differences in the contact angles of the particles. 14 Furthermore, we find that the phase of initial dispersion is extremely influential in determining the resulting emulsion type and 15 droplet size.
Interfacial activity of non-amphiphilic particles in fluid-fluid interfaces
Langmuir : the ACS journal of surfaces and colloids, 2017
Surfactants can adsorb in fluid-fluid interfaces and lower the interfacial tension. Like surfactants, particles with appropriate wettability can also adsorb in fluid-fluid interfaces. Despite many studies of particle adsorption at fluid interfaces, some confusion persists regarding the ability of (simple, non-amphiphilic) particles to reduce the interfacial tension. In the present work, the interfacial activity of silica nanoparticles at air-water and hexadecane-water interfaces and of ethyl cellulose particles at the interface of water with trimethylolpropane trimethacrylate was analyzed through pendant drop tensiometry. Our measurements strongly suggest that the particles do significantly affect the interfacial tension provided that they have a strong affinity to the interface by virtue of their wettability and that no energy barrier to adsorption prevents them from reaching the interface. A simplistic model that does not explicitly account for any particle-particle interactions i...
Oil-in-Water Emulsions Stabilized by Highly Charged Polyelectrolyte-Grafted Silica Nanoparticles †
Langmuir, 2005
Fully sulfonated poly(styrenesulfonate) brushes were grown from the surface of colloidal silica particles and used to prepare stable trichloroethylene-in-water and heptane-in-water Pickering emulsions. These particles were highly charged and colloidally stable in water but could not be dispersed in trichloroethylene or heptane. Both two-phase (emulsion plus neat water) and three-phase (emulsion separating neat oil and water phases) systems were observed, with water-continuous emulsion phases in all cases. Emulsion phases containing as much as 83% (v/v) oil were stable for over six months. Poly(styrenesulfonate)-grafted particles were very efficient emulsifiers; stable emulsion phases were prepared when using as little as 0.04 wt% particles. The emulsifying effectiveness of the poly(styrenesulfonate)-grafted silica particles can be attributed to the hydrophobicity of the vinylic polymer backbone that makes this highly charged polyelectrolyte unusually surface active at the oil/water interface. † Part of the Bob Rowell Festschrift special issue.
Molecular Dynamics Study of Nanoparticles and Non-Ionic Surfactant at an OilWater Interface
2020
Nanoparticles (NPs) and surfactants can spontaneously concentrate at the interface between two immiscible liquids, such as oil and water. Systems of high oil-water interfacial area, such as emulsions, are the basis of many industries and consumer products. Although NPs and surfactants are currently incorporated into many of these applications, their mutual interfacial behavior is not completely understood. Here we present molecular dynamics simulations of NPs and non-ionic surfactant in the vicinity of an oil-water interface. It was found that in low concentration the surfactants and NPs show cooperative behavior in lowering the oil-water interfacial tension, while at higher surfactant concentration this synergy is attenuated. It was also found that binding of surfactants to the NP surface decreases the surfactant efficiency in lowering the interfacial tension, while concurrently creating a barrier to NP aggregation.