Although several strategies are now available to produce functional microcompartments analogous to primitive cell-like structures, little progress has been made in generating protocell constructs ...with self-controlled membrane permeability. Here we describe the preparation of water-dispersible colloidosomes based on silica nanoparticles and delineated by a continuous semipermeable inorganic membrane capable of self-activated, electrostatically gated permeability. We use crosslinking and covalent grafting of a pH-responsive copolymer to generate an ultrathin elastic membrane that exhibits selective release and uptake of small molecules. This behaviour, which depends on the charge of the copolymer coronal layer, serves to trigger enzymatic dephosphorylation reactions specifically within the protocell aqueous interior. This system represents a step towards the design and construction of alternative types of artificial chemical cells and protocell models based on spontaneous processes of inorganic self-organization.
Determining the interfacial energy of nanoparticles is very challenging via traditional methods that first require measuring the contact angle of several liquids of a sessile drop on pellets or ...capillary rise in powder beds. In this work, we propose an alternative way to model the interfacial energy of nanoparticles directly from emulsion phase inversion data in Pickering emulsions. This could establish itself as a universal and facile way to determine the polarity of nanoparticles relative to a series of standard particles without the need to measure contact angles. Pickering emulsions of several oils in water were generated with a series of snowman-like Janus nanoparticles (JNPs), whose polarity gradually increased with the size of the more polar lobe. Depending on the oil to water ratio and the JNPs lobe size, oil-in-water (o/w) or water-in-oil (w/o) Pickering emulsions were obtained and the affinity of the JNPs to either water or oil can be inferred from the evolution of the emulsion phase inversion curves with these parameters. We further demonstrate that by adopting a simple model for the work of adhesion of JNPs with the water and oil phases, one can quantitatively calculate the relative interfacial energy change of the JNPs with the liquid. In addition, a knowledge of the interfacial energy of nanoparticles is useful for employing these in suspension polymerization to create surface nanostructured materials. The o/w and w/o Pickering emulsions obtained from monomers, such as styrene, could be polymerized, resulting in colloidosomes or hollow-like materials. The hollow materials exhibited a rather high volume storage capacity for the aqueous phase for extended periods of time, which could be released upon microwaving, making them ideal for use in long-term storage applications of various water-soluble actives.
Liquid marbles have promising applications in the field of microreactors, where the opening and closing of their surfaces plays a central role. We have levitated liquid water marbles using an ...acoustic levitator and, thereby, achieved the manipulation of the particle shell in a controlled manner. Upon increasing the sound intensity, the stable levitated liquid marble changes from a quasi-sphere to a flattened ellipsoid. Interestingly, a cavity on the particle shell can be produced on the polar areas, which can be completely healed when decreasing the sound intensity, allowing it to serve as a microreactor. The integral of the acoustic radiation pressure on the part of the particle surface protruding into air is responsible for particle migration from the center of the liquid marble to the edge. Our results demonstrate that the opening and closing of the liquid marble particle shell can be conveniently achieved via acoustic levitation, opening up a new possibility to manipulate liquid marbles coated with non-ferromagnetic particles.
A stable oil-in-water Pickering emulsion stabilized by negatively charged silica nanoparticles hydrophobized in situ with a trace amount of a conventional cationic surfactant can be rendered unstable ...on addition of an equimolar amount of an anionic surfactant. The emulsion can be subsequently restabilized by adding a similar trace amount of cationic surfactant along with rehomogenization. This destabilization–stabilization behavior can be cycled many times, demonstrating that the Pickering emulsion is switchable. The trigger is the stronger electrostatic interaction between the oppositely charged ionic surfactants compared with that between the cationic surfactant and the (initially) negatively charged particle surfaces. The cationic surfactant prefers to form ion pairs with the added anionic surfactant and thus desorbs from particle surfaces rendering them surface-inactive. This access to switchable Pickering emulsions is easier than those employing switchable surfactants, polymers, or surface-active particles, avoiding both the complicated synthesis and the stringent switching conditions.
Ultra-stable self-foaming oils Binks, Bernard P.; Marinopoulos, Ioannis
Food research international,
20/May , Letnik:
95
Journal Article
Recenzirano
Odprti dostop
This paper is concerned with the foaming of a range of fats in the absence of added foaming agent/emulsifier. By controlling the temperature on warming from the solid or cooling from the melt, ...crystals of high melting triglycerides form in a continuous phase of low melting triglycerides. Such crystal dispersions in oil can be aerated to produce whipped oils of high foamability and extremely high stability. The foams do not exhibit drainage and bubbles neither coarsen nor coalesce as they become coated with solid crystals. The majority of the findings relate to coconut oil but the same phenomenon occurs in shea butter, cocoa butter and palm kernel stearin. For each fat, there exists an optimum temperature for foaming at which the solid fat content reaches up to around 30%. We demonstrate that the oil foams are temperature-responsive and foam collapse can be controllably triggered by warming the foam to around the melting point of the crystals. Our hypothesis is given credence in the case of the pure system of tristearin crystals in liquid tricaprylin.
•Stable air-in-oil foams without added foaming agent•Crystals of high melting solid fat coat air bubbles in liquid oil of low melting fat•Temperature-responsive oil foams
Display omitted
Despite their wide utility in laboratory synthesis and industrial fabrication, gas–water–solid multiphase catalysis reactions often suffer from low reaction efficiency because of the low solubility ...of gases in water. Using a surface-modification protocol, interface-active silica nanoparticles were synthesized. Such nanoparticles can assemble at the gas–water interface, stabilizing micrometer-sized gas bubbles in water, and disassemble by tuning of the aqueous phase pH. The ability to stabilize gas microbubbles can be finely tuned through variation of the surface-modification protocol. As proof of this concept, Pd and Au were deposited on these silica nanoparticles, leading to interface-active catalysts for aqueous hydrogenation and oxidation, respectively. With such catalysts, conventional gas–water–solid multiphase reactions can be transformed to H2 or O2 microbubble reaction systems. The resultant microbubble reaction systems exhibit significant catalysis efficiency enhancement effects compared with conventional multiphase reactions. The significant improvement is attributed to the pronounced increase in reaction interface area that allows for the direct contact of gas, water, and solid phases. At the end of reaction, the microbubbles can be removed from the reaction systems through changing the pH, allowing product separation and catalyst recycling. Interestingly, the alcohol oxidation activation energy for the microbubble systems is much lower than that for the conventional multiphase reaction, also indicating that the developed microbubble system may be a valuable platform to design innovative multiphase catalysis reactions.
A novel charge‐reversible surfactant, (CH3)2N‐(CH2)10COONa, was designed and synthesized, which together with silica nanoparticles can stabilize a smart n‐octane‐in‐water emulsion responsive to pH. ...At high pH (9.3) the surfactant is anionic carboxylate, which together with the negatively charged silica nanoparticles co‐stabilize flowable oil‐in‐dispersion emulsions, whereas at low pH (4.1) it is turned to cationic form by forming amine salt which can hydrophobize in situ the negatively charged silica nanoparticles to stabilize viscous oil‐in‐water (O/W) Pickering emulsions. At neutral pH (7.5), however, this surfactant is converted to zwitterionic form, which only weakly hydrophobises the silica particles to stabilize O/W Pickering emulsions of large droplet size. Moreover, demulsification can be achieved rapidly triggered by pH. With this strategy particles can be controlled either dispersed in water or adsorbed at the oil‐water interface endowing emulsions with the capacity for intelligent and precise control of stability as well as viscosity and droplet size.
An emulsion was stabilized by silica particles in combination with a charge‐reversible surfactant, which can be converted between anionic, zwitterionic and cationic forms by pH trigger. Not only can rapid demulsification be achieved, but the emulsion can also be reversibly switched between an oil‐in‐dispersion emulsion and a Pickering emulsion. This strategy endows the emulsion with the capacity for intelligent and precise control of stability as well as viscosity and droplet size.
A dual stimuli-responsive n-octane-in-water Pickering emulsion with CO2/N2 and light triggers is prepared using negatively charged silica nanoparticles in combination with a trace amount of dual ...switchable surfactant, 4-butyl-4-(4-N,N-dimethylbutoxyamine) azobenzene bicarbonate (AZO-B4), as stabilizers. On one hand, the emulsion can be transformed between stable and unstable at ambient temperature rapidly via the N2/CO2 trigger, and on the other hand, a change in droplet size of the emulsion can occur upon light irradiation/rehomogenization cycles without changing the particle/surfactant concentration. The dual responsiveness thus allows for a precise control of emulsion properties. Compared with emulsions stabilized by specially synthesized stimuli-responsive particles or by stimuli-responsive surfactants, the method reported here is much easier and requires a relatively low concentration of surfactant (≈1/10 cmc), which is important for potential applications.
Responsive Photonic Liquid Marbles Anyfantakis, Manos; Jampani, Venkata S. R.; Kizhakidathazhath, Rijeesh ...
Angewandte Chemie (International ed.),
October 19, 2020, Letnik:
59, Številka:
43
Journal Article
Recenzirano
Odprti dostop
Liquid marbles have potential to serve as mini‐reactors for fabricating new materials, but this has been exploited little and mostly for conventional chemical reactions. Here, we uncover the ...unparalleled capability of liquid marbles to act as platforms for controlling the self‐assembly of a bio‐derived polymer, hydroxypropyl cellulose, into a cholesteric liquid crystalline phase showing structural coloration by Bragg reflection. By adjusting the cholesteric pitch via quantitative water extraction, we achieve liquid marbles that we can tailor for structural color anywhere in the visible range. Liquid marbles respond with color change that can be detected by eye, to changes in temperature, exposure to toxic chemicals and mechanical deformation. Our concept demonstrates the advantages of using liquid marbles as a miniature platform for controlling the liquid crystal self‐assembly of bio‐derived polymers, and their exploitation to fabricate sustainable, responsive soft photonic objects.
We exploit liquid marbles as miniature platforms for controlling the self‐assembly of hydroxypropyl cellulose into a cholesteric liquid crystal that shows structural coloration by Bragg reflection. By adjusting the self‐assembly parameters, we can tailor for structural color anywhere in the visible. Liquid marbles respond with color changes that can be detected by eye, to changes in temperature, compression, and exposure to toxic chemicals.
Display omitted
•A strategy to prepare ultra-stable aqueous foams using hydrophobic silica particles and hydrophilic polymer/colloids.•With hydrophilic polymer, the hydrophobic particles and polymer ...co-adsorb at air/water interface and form a Janus bilayer stabilizing foams in a synergistic manner.•This provides a convenient and time saving alternative to particle surface modification for foam stabilization, which broadens the range of suitable particles and scales up processing.•The stability of foams enables the fabrication of bulk lightweight and load-bearing porous materials which exhibited excellent tunability.
Interfacial assembly between nanoparticles and complementary ligands can in-situ generate Janus-like particles, rendering high stability of a Pickering-based system. Hence, through the self-assembly and formation of a Janus structure at the air/water interface, which is composed of a hydrophobic particle layer in the inner air phase and then a hydrophilic polymer layer in the aqueous phase, it should be possible to fabricate ultra-stable Pickering foams.
Foams containing different highly hydrophobic particles and hydrophilic polymers or microgels were prepared, and their stability was investigated. The interfacial structure of the Pickering bubbles was examined, where a new mechanism for ultra-stable foam formation was established. The properties of the foams were further demonstrated.
The interfacial co-assembly exploiting binary foam stabilizers being very hydrophobic particles and a hydrophilic polymer/particle results in the formation of ultra-stable Pickering foams. The generation of a Janus bilayer at the interface is the key factor responsible for their high stability. This strategy can be universally applied to any kind of highly hydrophobic particle with various hydrophilic polymers or colloids. The obtained foams demonstrate excellent tunability and plasticity, which could be used for mold-casting and printing.
PDF
