The versatility of colloidal particles endows the particle stabilized or Pickering emulsions with unique features and can potentially enable the fabrication of a wide variety of derived materials. We ...review the evolution and breakthroughs in the research on the use of colloidal particles for the stabilization of Pickering emulsions in recent years for the particle categories of inorganic particles, polymer-based particles, and food-grade particles. Moreover, based on the latest works, several emulsions stabilized by the featured particles and their derived functional materials, including enzyme immobilized emulsifiers for interfacial catalysis, 2D colloidal materials stabilized emulsions as templates for porous materials, and Pickering emulsions as adjuvant formulations, are also summarized. Finally, we point out the gaps in the current research on the applications of Pickering emulsions and suggest future directions for the design of particulate stabilizers and preparation methods for Pickering emulsions and their derived materials.
This review describes the various applications derived from Pickering emulsions focusing on several different categories based on the particle stabilizers comprised by inorganic particles, polymer particles, food-grade particles, and several composite particles and newly-discovered 2D material particles. Display omitted
•We review the evolution and breakthroughs in the research on the use of colloidal particles for the stabilization of Pickering emulsions in recent years for the particle categories of inorganic particles, polymer-based particles, and food-grade particles.•We discuss recent emulsions stabilized by the featured particles and their derived functional materials, including enzyme immobilized emulsifiers for interfacial catalysis, 2D colloidal materials stabilized emulsions as templates for porous materials, and Pickering emulsions as adjuvant formulations.•We point out the gaps in the current research on the applications of Pickering emulsions and suggest future directions for the design of particulate stabilizers and preparation methods for Pickering emulsions and their derived materials.
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•The synergistic effect of SDS/δ-FeOOH and H2O2 enhanced the removal of Tl.•The removal capacity of Tl and U from wastewater was as high as 182.9 and 359.6 mg/g, respectively.•The ...adsorption data of Tl and U are well consistent with the Freundlich isotherm model.•Precipitation, ion exchange, and surface oxidation and complexation contributed to the removal of Tl(III) and U(VI).•SDS/δ-FeOOH can function appropriately in seriously contaminated media.
Thallium (Tl) and uranium (U) contaminants pose serious threats to the ecological environment and human health. In this research, a cost-effective feroxyhite (δ-FeOOH) dispersed with sodium dodecyl sulfonate (SDS) was prepared and a series of experiments were optimized to explore the removal mechanism of Tl+ and UO22+ from the effluent. The SDS/δ-FeOOH exhibited highly dispersed colloidal particles and showed significantly enhanced adsorption performance on the removal of Tl and U in the presence of H2O2 and pH of 7.0. Equilibrium uptakes of 99.5% and 99.7% were rapidly achieved for Tl+ and UO22+ within 10 min, respectively. The Freundlich isotherm model fitted well with the adsorption data of Tl and U. The maximum isotherm sorption capacity of SDS/δ-FeOOH for Tl+ and UO22+ was 182.9 and 359.6 mg/g, respectively. The sorption of Tl followed the pseudo-second-order kinetic model, whereas the sorption of U followed the pseudo-first-order kinetic model. The uptake of Tl and U by SDS/δ-FeOOH was notably inhibited at Na+, K+ concentrations over 5.0 mM, and a high content of dissolved organic matter (over 0.5 mg/L). The mechanistic study revealed that ion exchange, precipitation, and surface complexation were main mechanisms for the removal of Tl and U. The findings of this study indicate that stabilizer dispersion may serve as an effective strategy to facilitate the treatment of wastewater containing Tl and U by using δ-FeOOH.
High internal phase Pickering emulsions Bago Rodriguez, Ana Maria; Binks, Bernard P.
Current opinion in colloid & interface science,
February 2022, 2022-02-00, Letnik:
57
Journal Article
Recenzirano
Macroemulsions rendered stable by adsorbed colloidal particles are termed Pickering emulsions. If the volume fraction of dispersed phase exceeds around 0.75, the emulsions are named high internal ...phase Pickering emulsions abbreviated to HIPPEs, which present new properties and potential applications. We review here the recent progress in preparing and studying HIPPEs of both oil-in-water and water-in-oil types. This includes discussion of the range of solid particle emulsifiers, the choice of the two immiscible liquids and methods for their preparation. As a result of their high interfacial area and long-term stability, HIPPEs are being put to use in many potential applications including drug delivery, catalysis, and in the production of novel porous materials.
Zein, a water insoluble plant protein from a renewable natural source, has been identified as a highly promising material for the production of protein-based colloidal particles for the encapsulation ...of lipophilic compounds. However, the encapsulation of hydrophilic, water-soluble, bioactive molecules within zein colloidal particles is still unexplored. We show that the encapsulation of epigallocatechin gallate (EGCG) is strongly limited by the weak physical interactions occurring with the zein matrix during the precipitation phase. We demonstrate that the use of sodium caseinate, as a colloidal stabilizer to coat the zein particles, enables the modulation of the encapsulation efficiency and functionality of zein colloidal particles for EGCG delivery. In particular, coated zein particles exhibit a larger size, opposite surface charge and significantly different antioxidant activity, owing to the localization of EGCG affected by the different extent of interaction of EGCG with zein and sodium caseinate. Remarkably, particle formulation also tunes the release rate of EGCG during in vitro digestion and modulates the rate of fat digestion, through the combination of the Pickering emulsion stabilization effect and EGCG interaction with lipase enzyme. Zein-based colloidal particles constitute hence remarkable systems for the tunable and multi-functional delivery of EGCG.
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•Zein-based colloidal particles as carriers for epigallocatechin gallate (EGCG).•Zein particles coated by sodium caseinate increase encapsulation efficiency.•EGCG release during in vitro digestion depends on carrier formulation.•EGCG-loaded zein-based particles modulate the rate of lipid digestion.
Particle surface chemistry and internal softness are two fundamental parameters in governing the mechanical properties of dense colloidal suspensions, dictating structure and flow, therefore of ...interest from materials fabrication to processing.
Here, we modulate softness by tuning the crosslinker content of poly(N-isopropylacrylamide) microgels, and we adjust their surface properties by co-polymerization with polyethylene glycol chains, controlling adhesion, friction and fuzziness. We investigate the distinct effects of these parameters on the entire mechanical response from restructuring to complete fluidization of jammed samples at varying packing fractions under large-amplitude oscillatory shear experiments, and we complement rheological data with colloidal-probe atomic force microscopy to unravel variations in the particles' surface properties.
Our results indicate that surface properties play a fundamental role at smaller packings; decreasing adhesion and friction at contact causes the samples to yield and fluidify in a lower deformation range. Instead, increasing softness or fuzziness has a similar effect at ultra-high densities, making suspensions able to better adapt to the applied shear and reach complete fluidization over a larger deformation range. These findings shed new light on the single-particle parameters governing the mechanical response of dense suspensions subjected to deformation, offering synthetic approaches to design materials with tailored mechanical properties.
In this work, we report for the first time the use of bacterial cellulose nanofibers/soy protein isolate (BCNs/SPI) composite colloidal particles as nature materials to be an effective particle ...stabilizer for the development of high internal phase emulsion (HIPE, oil-in-water) with 75% oil phase. The composite colloidal particles were prepared by an antisolvent approach, and the characterizations of the prepared composite colloidal particles with different BCNs/SPI ratios (1:25, 3:25, 5:25, 7:25 and 9:25 w/w) were investigated in the present work. FTIR analysis showed that BCNs/SPI colloidal particles were formed mainly through hydrogen bonds. The rheological property, crystallinity, thermal stability, and wettability of BCNs/SPI colloidal particles were improved as compared with pure SPI. Furthermore, the stability of HIPEs increased with the increase of BCNs/SPI ratios, where HIPEs stabilized by BCNs/SPI composite colloid particles with a ratio of 7:25 showed the highest stability during a 2-month storage period. Therefore, this study suggested that BCNs significantly improved the emulsifying capacity of SPI and the prepared BCNs/SPI composite colloids particles have great potential applications in the food industry.
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•The properties of BCNs/SPI colloidal particles were improved as compared with SPI.•BCNs/SPI colloidal particles formed a gel-like network at the oil-water interface.•BCNs improved the emulsifying capacity of SPI as a stabilizer for HIPEs.•BCNs/SPI colloidal particles show a great potential of application in food industry.
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•Ultrasound-generated turbulence is used to generate stable emulsion gels.•A new mechanism for producing stable emulsion gels is proposed.•Inter-droplet bridging and void filling by ...colloidal particles are crucial to generate stable emulsion gels.•The properties of emulsion gels could be tailored for specific applications.
Emulsion gels have a wide range of applications. We report on a facile and versatile method to produce stable emulsion gels with tunable rheological properties. Gel formation is triggered by subjecting a mixture containing aqueous colloidal particle (CP) suspensions and water-immiscible liquids to intense turbulence, generated by low frequency (20 kHz) ultrasound or high-pressure homogenization. Through systematic investigations, requisite gel formation criteria are established with respect to both formulation and processing, including ratio/type of liquid pairs, CP properties, and turbulence conditions. Based on the emulsion microstructure and rheological properties, inter-droplet bridging and CP void-filling are proposed as universal stabilization mechanisms. These mechanisms are further linked to droplet-size scaling and sphere close-packing theory, distinctive from existing gel-conferring models. The study thereby provides the foundation for advancing the production of emulsion gels that can be tailored to a wide range of current and emerging applications in the formulation and processing of food, cosmetics or pharmaceutical gels, and in material science.
In this work, nine different plant materials (lettuce, broccoli, shepherd's purse, orange peel, tangerine peel, lemon peel, lotus root, yam, and ginkgo nut) were used to prepare whole-component ...colloidal particles through the media milling. The colloidal properties and applicability in forming and stabilizing Pickering emulsions were investigated. The results showed that some particles exhibited good interfacial wettability. These particles could spontaneously absorb at the oil-water interface and effectively decrease interfacial tension. Pickering emulsions stabilized by broccoli colloidal particles exhibited better homogeneity and exceptional stability. While others were unstable to creaming/sedimentation. After slight stratification, the Pickering emulsions stabilized by fruit peel colloidal particles formed a solid gel unexpectedly. The Pickering emulsions stabilized by starch-based colloidal particles were rapidly stratified and coalesced during storage. Colloidal particles prepared from green vegetables and fruit peels demonstrated superior emulsifying capabilities than starch-based colloidal particles. This study indicates that broccoli can be a renewable source of whole-component plant-based stabilizers. It will provide valuable information for the exploitation of natural particle stabilizers and expand the application of plant resources in the food industry.
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•Some whole-component plant-based particles exhibited good interfacial wettability.•All particles could effectively decrease interfacial tension.•Pickering emulsion stabilized by broccoli particles was stable and homogeneous.•Emulsions formed by fruit peel particles solidified into a gel after stratification.
The controlled patterning of polymeric surfaces at the micro- and nanoscale offers potential in the technological development of small-scale devices, particularly within the fields of photovoltaics, ...micro-optics and lab- and organ-on-chip, where the topological arrangement of the surface can influence a system's power generation, optical properties or biological function - such as, in the latter case, biomimicking surfaces or topological control of cellular differentiation.
One of the most promising approaches in reducing manufacturing costs and complexity is by exploitation of the self-assembling properties of colloidal particles. Self-assembly techniques can be used to produce colloidal crystals onto surfaces, which can act as replicative masks, as has previously been demonstrated with colloidal lithography, or templates in mold-replication methods with resolutions dependent on particle size. Within this context, a particular emerging interest is focused on the use of self-assembled colloidal crystal surfaces in polymer replication methods such as soft lithography, hot and soft embossing and nano-imprint lithography, offering low-cost and high-resolution alternatives to conventional lithographic techniques.
However, there are still challenges to overcome for this surface patterning approach to reach a manufacturing reliability and process robustness comparable to competitive technologies already available in the market, as self-assembly processes are not always 100% effective in organizing colloids within a structural pattern onto the surface. Defects often occur during template fabrication. Furthermore, issues often arise mainly at the interface between colloidal crystals and other surfaces and substrates. Particularly when utilized in high-temperature pattern replication processes, poor adhesion of colloidal particles onto the substrate results in degradation of the patterning template. These effects can render difficulties in creating stable structures with little defect that are well controlled such that a large variety of shapes can be reproduced reliably.
This review presents an overview of available self-assembly methods for the creation of colloidal crystals, organized by the type of forces governing the self-assembly process: fluidic, physical, external fields, and chemical. The main focus lies on the use of spherical particles, which are favorable due to their high commercial availability and ease of synthesis. However, also shape-anisotropic particle self-assembly will be introduced, since it has recently been gaining research momentum, offering a greater flexibility in terms of patterning. Finally, an overview is provided of recent research on the fabrication of polymer nano- and microstructures by making use of colloidal self-assembled templates.
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•Colloidal particles interactions are described.•Review of self-assembly techniques for colloidal crystal formation.•The use of colloidal crystal template for polymer nano-patterning is described.
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