Pickering emulsions responsive to CO₂/N₂ and light dual stimuli at ambient temperature

A dual stimulus-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/re-homogenization cycles without changing the particle/surfactant concentration. The dual responsiveness thus allows for a precise control of emulsion properties. Compared with emulsions stabilised by specially synthesized stimuli-responsive particles or by stimuli-responsive surfactants, the method reported here is much easier and requires relatively low concentration of surfactant (≈1/10 cmc), which is important for potential applications

Smart worm-like micelles responsive to CO₂/N₂ and light dual stimuli

CO₂/N₂ and light dual stimuli-reponsive worm-like micelles (WLMs) were obtained by addition of a relatively small amount of a switchable surfactant, 4-butyl-4´-(4-N,N-dimethylhexyloxy-amine) azobenzene bicarbonate (AZO-B6-CO₂), sensitive to the same triggers into a binary aqueous solution of cetyltrimethyl ammonium bromide (CTAB) and sodium salycilate (NaSal)

Study on the property of AI-Sn-Pb and its bush material clad with steel strip by liquid-solid bond rolling

AISn8Pb2Si25Cu0.8Cr0.2(ASP) is a new bush material with high performance, but its bad lasticity limits its application. By studying the effect of silicon content on the performance of this bush material, it was found that the alloy performance and the distribution of tin and lead were affected by the silicon content. When the silicon content was 2.5%,most of the silicon recipitated along the grain boundary, and most of the lead and tin located along the grain boundary continuously, this resulted in the decrease of the bush material's performance. When the silicon content decreased to 1.0%,it distributed more uniformly, the tin and lead phases were spheroidized and became discontinuous, the performance of ASP material was then greatly increased

Effect of magnetostatic field on microstructure of 5005 aluminum alloy sheet by roll-casting

The roll-casting technology of 5000 series aluminum alloy is one of the difficulties at present. Roll-casting technology was employed in this paper and high quality 5005 aluminum alloy sheets were fabricated successfully under different conditions. The solidification of melt in roll-casting process is the rapid directional solidification. The effect of magnetostatic field on microstructure of 5005 aluminum alloy sheet by roll-casting has been investigated and analyzed. The results indicate that imposing magnetostatic field can refine the grains of 5005 aluminum alloy

A secretory kinase complex regulates extracellular protein phosphorylation.

Although numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation

pH-responsive Pickering emulsions stabilized by silica nanoparticles in combination with a conventional zwitterionic surfactant

pH-responsive oil-in-water Pickering emulsions were prepared simply by using negatively charged silica nanoparticles in combination with a trace amount of a zwitterionic carboxyl betaine surfactant as stabilizer. Emulsions are stable to coalescence at pH 5 but phase separate completely at pH > 8.5. In acidic solution, the carboxyl betaine molecules become cationic allowing them to adsorb on silica nanoparticles via electrostatic interactions, thus hydrophobizing and flocculating them enhancing their surface activity. Upon increasing the pH, surfactant molecules are converted to witterionic form and significantly desorb from particles surfaces triggering de-hydrophobization and coalescence of oil droplets within the emulsion. The pH-responsive emulsion can be cycled between stable and unstable many times upon alternating the pH of the aqueous phase. The average droplet size in re-stabilized emulsions at low pH however increases gradually after four cycles due to the accumulation of NaCl. Experimental evidence including adsorption isotherms, zeta potentials, microscopy and three-phase contact angles is given to support the postulated mechanisms

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 (C3H7−NH+(C10COOH)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

Responsive aqueous foams stabilized by silica nanoparticles hydrophobized in situ with a conventional surfactant

In the recent past, switchable surfactants and switchable/stimulus-responsive surface-active particles have been of great interest. Both can be transformed between surface-active and surface-inactive states via several triggers, making them recoverable and reusable afterward. However, the synthesis of these materials is complicated. In this paper we report a facile protocol to obtain responsive surface-active nanoparticles and their use in preparing responsive particle-stabilized foams. Hydrophilic silica nanoparticles are initially hydrophobized in situ with a trace amount of a conventional cationic surfactant in water, rendering them surface-active such that they stabilize aqueous foams. The latter can then be destabilized by adding equal moles of an anionic surfactant, and restabilized by adding another trace amount of the cationic surfactant followed by shaking. The stabilization–destabilization of the foams can be cycled many times at room temperature. The trigger is the stronger electrostatic interaction between the oppositely charged surfactants than that between the cationic surfactant and the negatively charged particles. The added anionic surfactant tends to form ion pairs with the cationic surfactant, leading to desorption of the latter from particle surfaces and dehydrophobization of the particles. Upon addition of another trace amount of cationic surfactant, the particles are rehydrophobized in situ and can then stabilize foams again. This principle makes it possible to obtain responsive surface-active particles using commercially available inorganic nanoparticles and conventional surfactants

Native Electrospray and Electron-Capture Dissociation in FTICR Mass Spectrometry Provide Top-Down Sequencing of a Protein Component in an Intact Protein Assembly

The intact yeast alcohol dehydrogenase (ADH) tetramer of 147 kDa was introduced into a FTICR mass spectrometer by native electrospray. Electron capture dissociation of the entire 23+ to 27+ charge state distribution produced the expected charge-reduced ions and, more unexpectedly, 39 c-type peptide fragments that identified N-terminus acetylation and the first 55 amino acids. The results are in accord with the crystal structure of yeast ADH, which shows that the C-terminus is buried at the assembly interface, whereas the N-terminus is exposed, allowing ECD to occur. This remarkable observation shows promise that a top-down approach for intact protein assemblies will be effective for characterizing their components, inferring their interfaces, and obtaining both proteomics and structural biology information in one experiment

CO₂/N₂ triggered switchable Pickering emulsions stabilized by alumina nanoparticles in combination with a conventional anionic surfactant

Stable n-decane-in-water Pickering emulsions were prepared using positively charged alumina nanoparticles in combination with a trace amount of the anionic surfactant sodium dodecyl sulfate (SDS) as stabilizer. Particles were hydrophobized in situ by adsorption of surfactant enhancing their surface activity. Emulsions can be readily demulsified by addition of an equal amount of a switchable surfactant, N'-dodecyl-N,N-dimethylacetamidine (DDAA), which can be transformed between a surface-active amidinium/cationic form and a surface-inactive amidine/neutral form by bubbling CO₂ or N₂, respectively. Following addition of cationic DDAA which prefers to form ion pairs with SDS, desorption of SDS from particles surfaces occurs and alumina particles are rendered hydrophilic resulting in demulsification of the emulsion. However, by bubbling N₂ into the demulsified mixture, DDAA molecules are converted to the amidine/neutral form leading to collapse of the ion pairs and re-establishment of the in situ hydrophobization of particles. Stable Pickering emulsions can be prepared again following homogenization. This simple demulsification/re-stabilization cycle can be repeated several times. Experimental evidence including measurement of the adsorption isotherm, zeta potentials, extent of particle adsorption at droplets interfaces in emulsions and microscopy is given to support the postulated mechanisms