Compartmentalization of incompatible reagents within Pickering emulsion droplets for one-pot cascade reactions

It is a dream that future synthetic chemistry can mimic living systems to process multistep cascade reactions in a one-pot fashion. One of the key challenges is the mutual destruction of incompatible or opposing reagents, for example, acid and base, oxidants and reductants. A conceptually novel strategy is developed here to address this challenge. This strategy is based on a layered Pickering emulsion system, which is obtained through lamination of Pickering emulsions. In this working Pickering emulsion, the dispersed phase can separately compartmentalize the incompatible reagents to avoid their mutual destruction, while the continuous phase allows other reagent molecules to diffuse freely to access the compartmentalized reagents for chemical reactions. The compartmentalization effects and molecular transport ability of the Pickering emulsion were investigated. The deacetalization–reduction, deacetalization–Knoevenagel, deacetalization–Henry and diazotization–iodization cascade reactions demonstrate well the versatility and flexibility of our strategy in processing the one-pot cascade reactions involving mutually destructive reagents

High surface area, emulsion-templated carbon foams by activation of polyHIPEs derived from Pickering emulsions.

Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. By the addition of KOH, chemical activation of the materials is induced during carbonization, producing Pickering-emulsion templated carbon foams, or carboHIPEs, with tailorable macropore diameters and surface areas almost triple that of those previously reported. The retention of the customizable, macroporous open-cell structure of the poly(divinylbenzene) precursor and the production of a large degree of microporosity during activation leads to tailorable carboHIPEs with excellent surface areas

Pickering Emulsion and Derived Materials

Particle-stabilized emulsions, today often referred to as Pickering/Ramsden emulsions, are vital in many fields, including personal care products, foods, pharmaceuticals, and oil recovery. The exploitation of these Pickering emulsions for the manufacture of new functional materials has also recently become the subject of intense investigation. While much progress has been made over the past decade, Pickering emulsion still remains a rich topic since many aspects of their behavior have yet to be investigated. The present “Pickering Emulsion and Derived Materials” Special Issue aims to bring together research and review papers pertaining to the recent developments in the design, fabrication, and application of Pickering emulsions. The themes include, but are not limited to: 1. Interactions of colloidal particles confined at fluid interfaces 2. Pickering emulsion-based polymerization 3. Interfacial assembly and emulsion stabilization 4. Rheology of particle laden interfaces and Pickering emulsions 5. Functional materials templated from Pickering emulsion

PICKERING EMULSION TECHNOLOGY IN FABRICATE CELLULOSE FOAM FROM OIL PALM EMPTY FRUIT BUNCH WASTE

PICKERING EMULSION TECHNOLOGY IN FABRICATE CELLULOSE FOAM FROM OILPALM EMPTY FRUIT BUNCH WASTE. Cellulose from the oil palm empty fruit bunch (OPEFB) waste can make a porous material. This study aims to make cellulose foam with Pickering emulsion technology used cellulose nanofiber as a Pickering agent. The mechanism of Pickering emulsion is learned from foamability and stability of foam in the presence of various concentrations of surfactant. The result showed that using Pickering emulsion technology only needed surfactant with a small concentration to improve foamability and stability. The addition of CNF indeed improved the stability and foamability with the Pickering effect. The stability test shows that the foam stabilized with CNF appeared to be relatively stable. In contrast to the CNF free system, the foams were collapse in three days tested. Structures of foam was characterized using an optical microscope and showed that the foam was composed into two- or three dimensional microstructures formed by gas bubble of wet foam in random orientations. This process generated the lightweight Cellulose foam from OPEFB waste, with a density of 0.07 g/cm3. Using Pickering emulsion technology to make cellulose foam can be one way to overcome OPEFB waste and this foam is potential for various applications

Aging mechanism in tunable Pickering emulsion

We study the stability of a model Pickering emulsion system. A special counter-flow microfluidics set-up was used to prepare monodisperse Pickering emulsions, with oil droplets in water. The wettability of the monodisperse silica nanoparticles (NPs) could be tuned by surface grafting and the surface coverage of the droplets was controlled using the microfluidics setup. A surface coverage as low as 23$\%$ is enough to stabilize the emulsions and we evidence a new regime of Pickering emulsion stability where the surface coverage of emulsion droplets of constant size increases in time, in coexistence with a large amount of dispersed phase. Our results demonstrate that the previously observed limited coalescence regime where surface coverage tends to control the average size of the final droplets must be put in a broader perspective

Octenylsuccinate quinoa starch granule-stabilized pickering emulsion gels: preparation, microstructure and gelling mechanism

The development of emulsion gels has attracted increasing interests due to their potential applications as oil structuring templates and release-controlled carriers for sensitive lipid-soluble bioactive compounds. This work aimed to elucidate the importance of changing the degree of substitution (DS, 0.0072–0.0286) and oil volume fraction (Φ, 10–90%) to achieve octenylsuccinate (OS) quinoa starch granule-based Pickering emulsion gels. The gelation process, droplet size distribution, rheological properties and microstructure of Pickering emulsion gels formed at various DS and Φ values were evaluated. Octenylsuccinylation did not change the morphology or the granule size of quinoa starch but significantly increased the contact angle from 36.2° to 68.7°. OS quinoa starch granule-stabilized Pickering emulsion gels were formed at a DS of 0.0286 with Φ values ranging from 50 to 70%. At the Φ value of 70%, increasing DS progressively increased the apparent viscosity (η) and storage modulus (G′) of the emulsions as a result of the adsorption of more OS quinoa starch granules at the oil/water interface. Both η and G′ showed an increasing trend as a function of Φ (50–70%) at a DS value of 0.0286, and this was closely related to the microstructure of the formed emulsion gels. The network of OS quinoa starch-based Pickering emulsion gels at high Φ values (e.g., 60% and 70%) was mainly composed of compact “aggregated” oil droplets, which was largely attributed to the inter-droplet interactions. These results are of great help in understanding the gelling mechanism and the development of starch granule-based Pickering emulsion gels

The ability of breadfruit starch nanoparticlestabilized pickering emulsion for encapsulating cinnamon essential oil

Cinnamon essential oil (CO) is susceptible to decreased stability during storage, limiting its application in food products. Pickering emulsion stabilized by starch nanoparticles becomes a potential encapsulating method that can improve CO stability. This study aimed to investigate the ability of breadfruit starch nanoparticles-stabilized Pickering emulsion to encapsulate CO with various concentrations. Encapsulation process was carried out using the high-energy emulsification method with dispersing CO (0.05%; 0.1%; 0.5%; 1% w/w) in emulsion. The loading efficiency of CO and emulsion properties were evaluated. Retention of CO was also observed in 7 days-storage. Results showed that 0.5% and 1% CO were encapsulated effectively and stable in Pickering emulsion, with loading efficiency and CO retention ranging from 79.49-81.13% and 78.86-79.20%, respectively. The addition of 0.5% and 1% CO increased yellowness (+a*: 7.45-8.99) as well as decreased whiteness (+L*: 85.77-86.06) and viscosity (629.9-721.8 cP) of Pickering emulsion. However, differences in CO concentrations did not affect the emulsion index of Pickering emulsion. These findings concluded that breadfruit starch nanoparticles-stabilized Pickering emulsion could encapsulate up to 0.5% and 1% CO with the best properties among other treatments. Therefore, breadfruit starch nanoparticlesstabilized Pickering emulsion can be an alternative as encapsulation method, which can later expand the application of CO in food products

Pickering Emulsions for the Emulsion Stability and Skin Delivery of Flavonoids using different Oil Types

Introduction A Pickering emulsion (PE) is a particle stabilised emulsion. Due to the amphiphilic structure of some flavonoids, they can form good stable PE. The use of Pickering emulsions serve as a potential useful approach for improving the formulation solubility of flavonoids, as well as reducing skin irritancy for topical formulations by removing emulsifiers from cosmetic formulations. This research in this study is the first (to the authors knowledge) to investigate the skin release kinetics and permeation of the flavonoids incorporated into a Pickering emulsion. Changes to the barrier properties of porcine Stratum corneum (SC) in vivo were also evaluated by investigating lipid morphology changes of the stratum corneum post hoc after the application of the Pickering emulsion and skin permeation studies. Oil in water (O/W) Pickering emulsions were made with three flavonoids differing in structure and physiochemical properties; rutin, isoquercetin and quercetin, each with 20 % w/w of oil. Three types of oil were used to make the Pickering emulsions; paraffin (hydrocarbon oil), almond and coconut (vegetable). Pickering emulsion were made with a jet homogeniser. PEs were evaluated for emulsion structure. Skin permeation release kinetics were established using split thickness porcine skin (intact stratum corneum and epidermis) in a Franz diffusion set up over 24 hours using an infinite dose technique. They were benchmarked against comparison controls, using mixtures of oil and flavonoid (omitting high pressure homogenisation), which did not form PEs. Flavonoids permeating through the skin membrane were identified by Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). Various mathematical models from literature were used to describe the release kinetics of the flavonoids based on the permeation data. The morphology of the lipid chain packing in the SC was evaluated using Fourier Transfer Infrared (FT-IR) spectroscopy and subsequent analysis using a Gaussian curve fitting algorithm. iv Results Flavonoids were found to aggregate at the oil/water interface to form Pickering emulsions. From visual stability observations (low-high phase separation and creaming); rutin > isoquercetin > quercetin, and for oil types this order paraffin > almond ≥ coconut oil. High shear homogenisation is essential for Pickering emulsion formation, and PEs do not form spontaneously. Quercetin did not form a PE with coconut oil. FT-IR results indicated a change in lipid morphology from the CH2 symmetric stretching and the CH2 scissoring bandwidths. A greater disruption in the extracellular matrix lipid packing was observed from the flavonoid suspensions and oil mixtures more than the Pickering emulsions, indicating that when the flavonoids are coating the oil in a Pickering emulsion, it reduces oil exposure to the SC lipids. In addition, a change in lipid morphology was seen between flavonoids; with the effect being in the order rutin > isoquercetin > quercetin. For skin permeation assays, after 7 hours there was no difference between the amount of flavonoids released from the epidermis, regardless of flavonoid structure. At 24 hours there was significantly more rutin delivered from paraffin and almond oil suspension (control) than the corresponding Pickering Emulsion (P < 0.05) and significantly more isoquercetin was delivered from vegetable oils suspensions (control) than the corresponding Pickering Emulsion (P < 0.05). Quercetin from PEs was not released from the membrane, only from the suspension (control). When flavonoids are aggregated at the O/W interface in a PE it changes the release kinetics and SC/epidermal penetration due to flavonoids being held at the interface before emulsion collapse.From the % dose applied, flavonoids were delivered in the order isoquercetin > rutin for the PEs and quercetin > isoquercetin > rutin for non-emulsions. This follows the predicted permeability behaviour due to the physiochemical properties of those specific flavonoids

Synthesis and Photocatalytic Performance of TiO2-CNT and Magnetized Fe3O4-TiO2-CNT Multifunctional Hybrids: A Pickering Emulsion Platform for Organic Degradation

The oil and textile industries produce billions of gallons of wastewater containing toxic, and sometimes carcinogenic or mutagenic, chemicals that often disperse throughout wastewater as suspended oil droplets. Photocatalytic degradation is a promising method for organic degradation, but needs to be improved. Tuning the photoactivity of a photocatalyst, enhancing the reactor design, and ensuring a facile method to remove the photocatalysts from the purified wastewater will help photocatalysis become a realistic option for use in advanced water treatment plants. Thus, this study set out to engineer an efficient and reusable method to degrade dispersed organic chemicals, by combining the photocatalytic properties of titania (TiO2), the electronic and hydrophobic properties of carbon nanotubes (CNTs), the magnetic abilities of iron oxide magnetite (Fe3O4), and the novel reactor design of Pickering emulsions. In this study, CNTs were hybridized with TiO2 and magnetized with Fe3O4 following a sol-gel method in order to form TiO2-CNTs and magnetic Fe3O4-TiO2-CNTs. The nanohybrids were used to stabilize Pickering emulsions, and preliminary dye degradation was demonstrated.Chemical EngineeringCivil, Architectural, and Environmental Engineerin

Design of surface-active artificial enzyme particles to stabilize Pickering emulsions for high-performance biphasic biocatalysis

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Surface-active artificial enzymes (SAEs) are designed and constructed by a general and novel strategy. These SAEs can simultaneously stabilize Pickering emulsions and catalyze biphasic biotransformation with superior enzymatic stability and good re-usability; for example, for the interfacial conversion of hydrophobic p-nitrophenyl butyrate into yellow water-soluble p-nitrophenolate catalyzed by esterase-mimic SAE