Charge-Reversible Surfactant-Induced Transformation Between Oil-in-Dispersion Emulsions and Pickering Emulsions

Nanoparticle Surfactants at Complex Emulsion Interfaces

Using nanoparticle surfactants to stabilize the liquid-liquid interface has attracted significant attention for developing all-liquid constructs including emulsions and liquid devices. Here, an efficient strategy is demonstrated to stabilize complex emulsions that consist of multiphase droplets by using the co-assembly between the cellulose nanocrystal and amine-functionalized polystyrene. Cellulose nanocrystal surfactants (CNCSs) form and assembly in situ at the specified area of emulsion interface, showing a unique pH responsiveness due to their dynamic nature and allowing the reconfiguration of complex emulsion from encapsulated to Janus structures. Such complex emulsions can be further used as the templates to fabricate polymeric particles with hollow, semi-spherical, and spherical shapes on large scale. These findings establish a promising platform for designing intelligent soft matter that can be used in microreactors, sensors, and anisotropic materials.

pH-Controllable Redox Responsive Amphiphilic Viologens for Switchable Emulsions

A pH and redox dual responsive amphiphilic viologen is synthesized, which can be reversibly transformed among the zwitterionic (SVa), monovalent anionic (SV+), and divalent anionic (SVH2+) forms upon pH variation, exhibiting pH-controllable redox responsive properties. Switchable Pickering emulsions with different droplet size and viscosity are prepared by the mixture of hydrophilic silica nanoparticles and the viologens (SV+ or SVH2+) at acidic conditions, while such combination yielded an oil-in-dispersion emulsion at neutral pH value. Not only can rapid reversible demulsification/stabilization of the Pickering emulsions be achieved by redox reactions, but the rate of redox-demulsification can also be controlled by pH trigger. The dual-responsive amphiphilic viologens have potential applications in developing intelligent colloid materials and molecular logic systems.

Waste for Waste: Interface-Intensified Durable Superhydrophilic-Superoleophobic Collagen Fiber Membrane for Efficient Separation of Cationic Surfactant-Stabilized Oil-in-Water Emulsions

Cationic surfactant-stabilized oil-in-water emulsions pose a significant challenge in separation due to the presence of surfactants. Herein, we develop a collagen-fiber-based CFM-PMDA-TiO2 membrane with unique infiltration properties capable of efficiently separating cationic surfactant-stabilized oil-in-water emulsions by exploiting the charge-demulsification effect. The membrane exhibits superhydrophilic and submerged superoleophobic properties, making it highly suitable for separating a wide range of commercially available cationic surfactant-stabilized oil-in-water microemulsions and nanoemulsions, which demonstrates an exceptional separation efficiency as high as 99.86% and an impressive flux of up to 1436.40 L m-2 h-1. Furthermore, even after a strong subjecting of the membrane to sandpaper abrasion and a full 15 time use, the separation efficacy of oil-in-water emulsions is retained, highlighting the durability, reusability, and economic viability. We propose that these features are enabled by the electrostatic interactions triggered from pyromellitic dianhydride (PMDA) and superhydrophilic-superoleophobic membrane intensified by the TiO2 on the unique collagen fiber membrane. Outcomes emphasize the versatility and potential of our membrane in addressing emulsified oily wastewater hurdles.

Structured Emulgels by Interfacial Assembly of Terpenes and Nanochitin

Interfacial assemblies formed by colloidal complexation are effective in multiphase stabilization, as shown in structured liquids and Pickering emulgels. Herein, we demonstrate a type of biobased colloidal system that spontaneously stabilizes an organic phase in a continuous hydrogel phase. Specifically, a triterpene extracted from bark (betulin, BE) is added to an organic phase containing a coniferous resin (rosin acid, a diterpene). BE is shown to take part in strong noncovalent interactions with the nanochitin dispersed in the aqueous (hydrogel) phase, leading to a complex of high interfacial activity. The viscoelastic response of the system is rationalized by the presence of a superstable structured dual network. When used as a templating material, the emulgel develops into structured liquids and cryogels. The herein introduced all-biobased type of nanoparticle surfactant system forms a gel ("emulsion-filled" with "aggregated droplets") that features the functional benefits of both betulin and nanochitin.

Reversible Emulsions from Polyoxometalate-Polymer: A Robust Strategy to Cyclic Emulsion Catalysis and High-Internal-Phase Emulsion Materials

Reversible Pickering emulsions, achieved by switchable, interfacially active colloidal particles, that enable on-demand emulsification/demulsification or phase inversion, hold substantial promise for biphasic catalysis, emulsion polymerization, cutting fluids, and crude oil pipeline transportation. However, particles with such a responsive behavior usually require complex chemical syntheses and surface modifications, limiting their extensive use. Herein, we report a simple route to generate emulsions that can be controlled and reversibly undergo phase inversion. The emulsions are prepared and stabilized by the interfacial assembly of polyoxometalate (POM)-polymer, where their electrostatic interaction at the interface is dynamic. The wettability of the POMs that dictates the emulsion type can be readily regulated by tuning the number of polymer chains bound to POMs, which, in turn, can be controlled by varying the concentrations of both components and the water/oil ratio. In addition, the number of polymer chains anchored to the POMs can be varied by controlling the number of negative charges on the POMs through an in situ redox reaction. As such, a reversible inversion of the emulsions can be triggered by switching between exposure to ultraviolet light and the introduction of oxygen. Combining the functions of POM itself, a cyclic interfacial catalysis system was realized. Inversion of the emulsion also affords a pathway to high-internal-phase emulsions. The diversity of the POMs, the polymers, and the responsive switching groups open numerous new, simple strategies for designing a wide range of responsive soft matter for cargo loading, controlled release, and delivery in biomedical and engineering applications without time-consuming particle syntheses.

Smart Emulsions Stabilized by a Multi-headgroup Surfactant Tolerant to High Concentrations of Acids and Salts

Retaining emulsions stable at high acidity and salinity is still a great challenge. Here, we report a novel multi-headgroup surfactant (C3 H7 -NH+ (C10 COOH)2 , di-UAPAc) which can be reversibly transformed among cationic, anionic and zwitterionic forms upon pH variation. Stable oil-in-dispersion (OID) emulsions in strong acidity (pH=2) can be co-stabilized by low concentrations of di-UAPAc and silica nanoparticles. High salinity at pH=2 improves the adsorption of di-UAPAc on silica particles through hydrogen bonding, resulting in the transformation of OID emulsions into Pickering emulsions. Moreover, emulsification/demulsification and interconversion between OID and Pickering emulsions together with control of the viscosity and droplet size can be triggered by pH. The present work provides a new protocol for designing surfactants for various applications in harsh aqueous media, such as strong acidity and high salinity, involved in oil recovery and sewerage treatments.

A Review on Edible Coatings and Films: Advances, Composition, Production Methods, and Safety Concerns

Food is a crucial source for the endurance of individuals, and quality concerns of consumers are being raised with the progression of time. Edible coatings and films (ECFs) are increasingly important in biobased packaging because they have a prime role in enhancing the organoleptic characteristics of the food products and minimizing the spread of microorganisms. These sustainable ingredients are crucial for a safer and healthier environment. These are created from proteins, polysaccharides, lipids, plasticizers, emulsifiers, and active substances. These are eco-friendly since made from innocuous material. Nanocomposite films are also beginning to be developed and support networks of biological polymers. Antioxidant, flavoring, and coloring compounds can be employed to improve the quality, wellbeing, and stability of packaged foods. Gelatin-enhanced fruit and vegetable-based ECFs compositions have the potential to produce biodegradable films. Root plants like cassava, potato, and sweet potato have been employed to create edible films and coatings. Achira flour, amylum, yam, ulluco, and water chestnut have all been considered as novel film-forming ingredients. The physical properties of biopolymers are influenced by the characteristics, biochemical confirmation, compatibility, relative humidity, temperature, water resistance, and application procedures of the components. ECFs must adhere to all regulations governing food safety and be generally recognized as safe (GRAS). This review covers the new advancements in ECFs regarding the commitment of novel components to the improvement of their properties. It is expected that ECFs can be further investigated to provide innovative components and strategies that are helpful for global financial issues and the environment.

Design of Proanthocyanidins and TiO2 Nanoparticles-Based Novel Emulsions as a Platform for UV Protection

A white oil-in-water novel emulsion stabilized by TiO2 nanoparticles with UVB shielding properties and proanthocyanidins with antioxidant activity was prepared, where the proanthocyanidins aggregated at the oil-water interface to reduce interfacial tension while TiO2 nanoparticles were dispersed in the continuous water phase to hinder droplet coalescence. It was found that the average oil droplet size was less than 10 μm and decreased with the increase of proanthocyanidins concentration, but the increase of the content of TiO2 nanoparticles had little effect on it. The combination of TiO2 nanoparticles and proanthocyanidins was versatile for oil phases with different polarities, and the resulting emulsion exhibited high stability in the face of centrifugation, heating and prolonging storage time. After encapsulating the UVA filter avobenzone in white oil, the emulsion was endowed with the ability to resist UVB and UVA. Further, the emulsion showed great free radical scavenging ability for superoxide anion radical (⋅O2 - ), hydroxyl radical (⋅OH) with the clearance rate of over 70 %, indicating the good antioxidant activity. The ingenious combination of UVB, UVA filter and antioxidant with emulsion as carrier provides a new idea for the preparation of full-band sunscreen emulsion.

Pluronic Induced Interparticle Attraction and Re-entrant Liquid-Liquid Phase Separation in Charged Silica Nanoparticle Suspensions

Tuning surface properties of nanoparticles by introducing charge, surface functionalization, or polymer grafting is central to their stability and applications. Here, we show that introducing non-DLVO forces like steric and hydrophobic effects in charged silica nanoparticle suspensions through interaction with a nonionic surfactant brings about interesting modulations in their interparticle interaction and phase behavior. The Ludox TM-40 negatively charged silica suspensions thus exhibit liquid-liquid phase separation driven by the onset of interparticle attraction in the system in the presence of the triblock copolymer Pluronic P123. The observed phase separations are thermoresponsive in nature, as they are associated with lower consolute temperatures and a re-entrant behavior as a function of temperature. The nanoparticle-Pluronic system thus undergoes transformation from one-phase to two-phase and then back to one-phase with monotonic increase in temperature. Evolution of the interparticle interaction in the composite system is investigated by dynamic light scattering (DLS), small angle neutron scattering (SANS), zeta potential, rheological, and fluorescence spectroscopy studies. Zeta potential studies show that the charge interaction in the system is partially mitigated through adsorption of a Pluronic micellar layer on the nanoparticle surfaces. Contrast-matching SANS studies suggest that hydrophobic interactions between the adsorbed micellar layer bring about the onset of interparticle attraction in the system. The results are unique and not reported hitherto in charged silica nanoparticle systems.

Facile modification of nanochitin in aqueous media for stabilizing tea tree oil based Pickering emulsion with prolonged antibacterial performance

Nanochitins have been explored for preparing Pickering Emulsions, however its application is restricted by its simplex disperse nature. It was hypothesized that zwitterionic nanochitins should be capable of stabilizing oil/water (O/W) interfaces in wider pH range. Furthermore, the control of their size, disperse nature and self-assembly performance suggest the formulation of tunable emulsions. Zwitterionic nanochitins were prepared via Schiff base reaction. A systematic study was performed analyzing the disperse nature, fibril morphology, surface characteristic of modified nanochitins. Oil-in-Water Pickering Emulsions stabilized by modified nanochitins were formulated and emulsion stability was analyzed as function of concentration, pH and self-assembly property and further applied for prolonged antibacterial applications. Comparing freshly prepared nanochitins, neutral/alkaline stably dispersed nanochitins can be prepared while maintaining fibril characteristics such as fibril size, crystallinity, thermal stability and so on. Better suspension stability of modified nanochitins under alkaline conditon together with the self assembly performance resulting from amino groups and carboxyl groups benefit the enhanced emulsion stability under nanochitins concentreation of 0.2 %. Encapsulation of tea tree oil in Pickering Emulsions prolongs the diffusion rate oil in the aqueous environment, thus resulting prolongs its antibacterial performance against E. coli and B. subtilis.

Charge Density Overcomes Steric Hindrance of Ferrocene Surfactant in Switchable Oil-in-Dispersion Emulsions

A ferrocene surfactant can be switched between single and double head form (FcN⁺ C₁₂ /Fc⁺ N⁺ C₁₂ ) triggered by redox reaction. FcN⁺ C₁₂ can neither stabilize an O/W emulsion alone nor an oil-in-dispersion emulsion in combination with alumina nanoparticles due to the steric hindrance of the ferrocene group. However, such steric hindrance can be overcome by increasing the charge density in Fc⁺ N⁺ C₁₂ , so that oil-in-dispersion emulsions can be co-stabilized by Fc⁺ N⁺ C₁₂ and alumina nanoparticles at very low concentrations (1×10^-7  M (≈50 ppb) and 0.001 wt %, respectively). Not only can reversible formation/destabilization of oil-in-dispersion emulsions be achieved by redox reaction, but also reversible transformation between oil-in-dispersion emulsions and Pickering emulsions can be obtained through reversing the charge of alumina particles by adjusting the pH. The results provide a new protocol for the design of surfactants for stabilization of smart oil-in-dispersion emulsions.

Novel Strategy of Polymers in Combination with Silica Particles for Reversible Control of Oil-Water Interface

Hybrid smart emulsification systems are highly applicable in manipulating oil-in-water (O/W) droplets. Herein, novel switchable block polymers containing both zwitterionic and tertiary amine pendent groups were designed and synthesized to combine with charged silica particles to stabilize the O/W emulsion responsive to pH. This study was carried out in O/W emulsions stabilized with the polymer and silica particles under different pH conditions. The emulsion system was also simulated using molecular dynamics simulation to reveal the mechanism at molecular levels, thus gaining insight into the relationships between the emulsifying properties and the molecular interaction of the mixed system. Upon acidification of the continuous aqueous phase, protonated polymers with excellent hydrophilicity were induced by charged silica particles to cause rapid emulsion coalescence. In alkaline media, the mixed system conversely stabilized the O/W emulsions, cutting polymer consumption by over three-quarters. The emulsification and demulsification can be switched alternately by tuning the pH conditions. The applications exhibited excellent efficiency in separating heavy oil/water emulsions and proved the high conversion rate in emulsion polymerization. Overall, with this novel strategy to relieve tedious modifications on particle surfaces and massive consumption of polymers, the designed responsive emulsification systems can impart intelligent and controllable chemical reactivity to emulsions on demand in a more affordable and sustainable way.

Pickering Emulsions Synergistically Stabilized by Aliphatic Primary Amines and Silica Nanoparticles

Innovation in emulsion compositions is necessary to enrich emulsion formulations and applications. Herein, Pickering emulsions were prepared using silica nanoparticles and aliphatic primary amines with an oil-water ratio of 1:1 (v/v). Contact angle experiments revealed that the in situ hydrophobization of nanoparticles was caused by the surface adsorption of amine molecules. Notably, the interactions between amine compounds and the surface of silica nanoparticles were electrostatic attractions and mutual hydrogen bonding. The existence of hydrogen bonds was further confirmed by demulsification experiments using a chaotropic agent DMF and increasing temperatures. The hydrophobicity of silica nanoparticles can be effectively improved using most commercially available aliphatic primary amines such as n-hexylamine, n-octylamine, n-decylamine, dodecylamine, and tetradecylamine. The minimum concentrations of the aforementioned amines necessary for stabilizing the emulsions with 0.3 wt % silica nanoparticles are 3, 0.6, 0.3, 0.06, and 0.03 mM, respectively, decreasing significantly with increasing alkyl chain length. With the increase of the amine concentrations, the hydrophobicity of silica particles monotonically increased and finally resulted in the inversion of emulsions. The amine concentrations for emulsion phase inversion were 150, 40, 30, 20, and 20 mM, respectively, in the presence of 0.3 wt % silica nanoparticles. In this work, silica nanoparticles were hydrophobized using aliphatic primary amines. The composite stabilizers developed are useful for developing novel stimuli-responsive Pickering emulsions, while the synergistic effects introduced herein are also helpful in expanding the hydrophobization methods available for nanoparticles.

3D-printable, lightweight, and electrically conductive metal inks based on evaporable emulsion templates jammed with natural rheology modifiers

Conductive metal inks with 3D-printable rheological properties have gained considerable attention, owing to their potential for manufacturing 3D electronics. Typically, such inks are formulated with high volume fractions of metal particles to achieve both rheological and electrical percolation. However, this leads to a high product cost and weight, making this approach potentially undesirable for practical application. In this study, naturally occurring ingredients, i.e., bee pollen microparticles (BPMPs) and citric acids (CAs), are used to produce a jammed hexane-in-aqueous suspension-type emulsion with controllable viscoelasticity as a template for conductive metal particles. Correspondingly, it is possible to develop 3D-printable, lightweight, and conductive inks. The BPMPs and CAs, as rheology modifiers, facilitate the 3D printability of the ink. After drying, the ink forms 3D networks without macroscopic discontinuities. Hexanes co-dispersed with BPMPs and CAs in the aqueous continuous phase improve the ink rheological processability and create internal macropores within the 3D-printed structure upon evaporation under ambient conditions, decreasing the product density. A conductive copper ink based on the emulsion template shows excellent 3D printability and electrical percolation at low metal loadings (<10 vol%); moreover, the printed ink with the optimized formulation has a remarkably low density (<2 g ∙ cm^-3).

Pickering Emulsion Catalysis: Interfacial Chemistry, Catalyst Design, Challenges, and Perspectives

Pickering emulsions are particle-stabilized surfactant-free dispersions composed of two immiscible liquid phases, and emerge as attractive catalysis platform to surpass traditional technique barrier in some cases. In this review, we have comprehensively summarized the development and the catalysis applications of Pickering emulsions since the pioneering work in 2010. The explicit mechanism for Pickering emulsions will be initially discussed and clarified. Then, summarization is given to the design strategy of amphiphilic emulsion catalysts in two categories of intrinsic and extrinsic amphiphilicity. The progress of the unconventional catalytic reactions in Pickering emulsion is further described, especially for the polarity/solubility difference-driven phase segregation, "smart" emulsion reaction system, continuous flow catalysis, and Pickering interfacial biocatalysis. Challenges and future trends for the development of Pickering emulsion catalysis are finally outlined.

Oil-in-Water emulsions stabilized by alumina nanoparticles with organic electrolytes: Fate of particles

HYPOTHESIS

Oil-in-dispersion emulsions can be stabilized by like charged particles and surfactant. Surfactant adsorbs at the oil-water interface to reduce the interfacial tension and endow the interface with charge, while particles remain dispersed in the aqueous phase to provide electrostatic repulsion between droplets and particles. Can weakly surface-active organic electrolytes adsorb at the oil-water interface and behave like surfactants in stabilizing oil-in-dispersion emulsions with like charged particles?

EXPERIMENTS

Symmetrical organic electrolytes, tetraalkylammonium bromides (R₄NBr), with either no or very low interfacial activity endowing oil droplets with charge were combined with alumina nanoparticles to stabilize emulsions. The effect of R chain length (varying from methyl to butyl) on the type and stability of emulsions was investigated.

FINDINGS

Mixtures of high concentrations of short chain R₄NBr salts (R = methyl or ethyl) and alumina particles stabilise oil-in-water Pickering emulsions, whereas longer chain (R = propyl or butyl) analogues stabilize oil-in-dispersion emulsions assisted by alumina particles. Tetrapropylammonium and tetrabutylammonium cations adsorb at the oil-water interface reducing the interfacial tension and endowing the interface with charge. The stability of the oil-in-dispersion emulsions is dominated by the electrostatic repulsion between the droplets and between droplets and particles in the continuous aqueous phase.

A Dual pH‐ and Light‐Responsive Spiropyran‐Based Surfactant: Investigations on Its Switching Behavior and Remote Control over Emulsion Stability

A cationic surfactant containing a spiropyran unit is prepared exhibiting a dual‐responsive adjustability of its surface‐active characteristics. The switching mechanism of the system relies on the reversible conversion of the non‐ionic spiropyran (SP) to a zwitterionic merocyanine (MC) and can be controlled by adjusting the pH value and via light, resulting in a pH‐dependent photoactivity: While the compound possesses a pronounced difference in surface activity between both forms under acidic conditions, this behavior is suppressed at a neutral pH level. The underlying switching processes are investigated in detail, and a thermodynamic explanation based on a combination of theoretical and experimental results is provided. This complex stimuli‐responsive behavior enables remote‐control of colloidal systems. To demonstrate its applicability, the surfactant is utilized for the pH‐dependent manipulation of oil‐in‐water emulsions.

Microfluidic macroemulsion stabilization through in situ interfacial coacervation of associative nanoplatelets and polyelectrolytes

HYPOTHESIS

Since macroemulsions tend to break down to lower free energy, they hardly retain their initial drop state. Therefore, studies are being conducted to overcome this based on advanced interface engineering techniques, but it is still challenging. Herein we hypothesize that the stability of giant droplets can be secured without chemical bonding through the interfacial coacervation of polyelectrolyte and associative nanoplatelets.

EXPERIMENTS

We synthesized associative silica nanoplates (ASNPs) via polypeptide-templated silicification and consecutive wettability adjustment. To produce monodisperse macrodroplets, the inner fluid containing partially positively charged ASNPs and the outer fluid dissolving negatively charged polyacrylic acid (PAA) were coflowed through a capillary-based microfluidic channel.

FINDINGS

Dynamic interfacial tension and interfacial rheology measurements revealed that the migration of ASNPs and PAA from each phase to the interface led to the formation of a complex bilayered thin membrane with an enhanced interfacial modulus. In addition, we demonstrated that adjusting the surface properties of ASNPs by coupling a fluorochemical enabled the production of monodisperse fluorocarbon-in-oil-in-water double macroemulsions. These results highlighted the applicability of our microfluidics-based interfacial coacervation technology in the development of complex fluid products with visual differentiation and drug encapsulation.

Multilayer-Stabilized Water-in-Water Emulsions

Water-in-water (W/W) emulsions are of interest for various applications due to their inherent biocompatibility, ultralow interfacial tensions, and large interface thickness. However, it is still challenging to prepare stable W/W emulsions with tailored phase architectures compared to oil-in-water (O/W) and water-in-oil (W/O) emulsions. Here, we report a multilayer-stabilized W/W emulsion composed of poly(ethylene glycol)/dextran in the presence of DNA strands. The W/W emulsions present onion-ring-like structures, which are interpreted by a nanofluid film model. Emulsion behavior, e.g., stability, interface tension, etc., can be controlled by the type of DNA (single or double strands), DNA concentration, and volume fraction of dispersed phase. Our findings could broaden the preparation of novel emulsions for potential applications in emulsion polymerization, new media of homogeneous catalysis, and DNA transportation of water-in-water media.

Cleanup of oiled shorelines using a dual responsive nanoclay/sodium alginate surface washing agent

Oil spills may affect ecosystems and endanger public health. In this study, we developed a novel and dual responsive nanoclay/sodium alginate (NS) washing fluid, and systematically evaluated its application potential in oiled shoreline cleanup. The characterization results demonstrated that sodium alginate combined with nanoclay via hydrogen bonds, and was inserted into the interlayer spacing of nanoclay. Adding sodium alginate reduced surface and interfacial tensions, while increasing the viscoelasticity of the washing fluid. Batch experiments were conducted to investigate oil removal performance under various conditions. Additionally, the factorial design analysis showed that three single factors (temperature, oil concentration, and salinity), and two interactive effects (temperature/salinity; and oil concentration/HA) displayed significant effects on the oil removal efficiency of the NS washing fluid. Compared to the commercial surfactants, the NS composite exhibited satisfactory removal efficiencies for treating oily sand. Green materials-stabilized Pickering emulsion can potentially be used for oil/water separation. The NS washing agent displayed excellent pH- and Ca²⁺- responsiveness, generating transparent supernatants with low oil concentration and turbidity. Our work opens an interesting avenue for designing economical, high performance, and green washing agents.

Temperature-responsive Pickering high internal phase emulsions for recyclable efficient interfacial biocatalysis

The field of biocatalysis is expanding owing to the increasing demand for efficient low-cost green chemical processes. However, a feasible strategy for achieving product separation, enzyme recovery, and high catalytic efficiency in biocatalysis remains elusive. Herein, we present thermoresponsive Pickering high internal phase emulsions (HIPEs) as controllable scaffolds for efficient biocatalysis; these HIPEs demonstrate a transition between emulsification and demulsification depending on temperature. Ultra-high-surface-area Pickering HIPEs were stabilized by Candida antarctica lipase B immobilized on starch particles modified with butyl glycidyl ether and glycidyl trimethyl ammonium chloride, thus simplifying the separation and reuse processes and significantly improving the catalytic efficiency. In addition, the switching temperature can be precisely tuned by adjusting the degree of substitution of the modified starches to meet the temperature demands of various enzymes. We believe that this system provides a green platform for various interfacial biocatalytic processes of industrial interest.

The thermoresponsive Pickering high internal phase emulsions stabilized by starch particles as controllable scaffolds for efficient biocatalysis, which simplified the separation and reuse processes and significantly improved the catalytic efficiency.

Conversion of bile salts from inferior emulsifier to efficient smart emulsifier assisted by negatively charged nanoparticles at low concentrations

Bile salts (BS), one of the biological amphiphiles, are usually used as solubilizing/emulsifying agents of lipids or drugs. However, BS such as sodium deoxycholate (NaDC) can't stabilize an oil-in-water (O/W) emulsion alone due to its unusual molecular structure. In this paper we report that these emulsifiers with poor emulsifying ability can be transformed to highly efficient emulsifiers by combining with negatively charged particles (silica or montmorillonite). Both together can synergistically co-stabilize oil-in-water emulsions at extremely low concentrations (minimum 0.01 mM NaDC plus 0.003 wt% particles). Moreover, the emulsions can be reversibly switched between stable and unstable triggered by CO₂/N₂ at room temperature. This strategy is universal for emulsions containing different oils (alkanes, aromatic hydrocarbons and triglycerides) and for different BS and offers a generic model for a variety of BS of different molecular structure, which will extend their applications in more technical fields such as emulsion polymerization, biphasic catalysis and emulsion extraction.

Bile salts can be converted to efficient emulsifiers assisted by a trace amount of similarly charged nanoparticles and the emulsions formed are CO₂/N₂ switchable at room temperature.