Samara C. SilvaThayńa AlmeidaGiovana ColucciArantzazu Santamaria-Echart...
10页
查看更多>>摘要：Spirulina (Arthrospira platensis) proteins have been proven to present emulsifying properties. In this work, a Spirulina protein-rich extract obtained by ultrasound extraction (SpE) was tested to stabilize oil-in-water (O/W) emulsions. For this purpose, a sequential experimental design strategy (Fractional Factorial Design (FFD) 2~(4-1) followed by a Central Composite Rotatable Design (CCRD) 2~2)) was applied. The effect of four variables, SpE concentration, O/W weight ratio, pH and storage time, on emulsions' zeta potential and number-mean droplet diameter was considered for the FFD 2~(4-1), indicating SpE concentration and storage time as the relevant variables for the CCRD 2~2. According to zeta potential and number-mean droplet diameter evaluation, for the studied SpE concentration range (2-5 wt%), quite stable emulsions were obtained along the tested 30-days period. Even so, for 5%, visual inspection revealed extract segregation after 20-days. The optimal solution comprised 4 wt% of SpE, for an O/W weight ratio of 30/70 and a pH of 7.0 (number-mean droplet diameter of 55.66 nm and zeta potential of - 43.83 mV). Overall, SpE has proven to be an excellent emulsifier, offering the potential to substitute animal-based proteins and synthetic emulsifiers. In addition, no signs of contamination by microorganisms were observed, suggesting that the SpE may also act as an antimicrobial agent.
查看更多>>摘要：Excessive pressure difference between hydrogen and oxygen generated from sodium borohydride might destroy proton exchange membrane, and too fast hydrogen production rate could even give rise to dangerous battery explosion. So it was urgent to encapsulate the surface of sodium borohydride with a controllable responsive polymeric shell for achieving the effective regulation of hydrogen generation. In this work, a core-shell capsule with sodium borohydride as the core and dopamine-containing copolymer as the shell was prepared. Trans-mission Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, Fourier transform infrared spectra and Nuclear Magnetic Resonance Spectroscopy verified successful synthesis of the desired capsule. The encapsulated sodium borohydride exhibited good chemical stability and reversible photo-crosslinking under ultraviolet light irradiation. The dopamine-containing copolymer as the shell layer could effectively protect sodium borohydride core layer from the damage of surrounding aquifer media. Hydrogen generation determination indicated that the rate and yield of hydrogen production of core-shell capsule could be well regulated to cope with the change of external conditions such as pH, sodium chloride and ultraviolet light. It seemed that core-shell capsule with the copolymeric encapsulation might have great potential application prospects in fuel cells.
查看更多>>摘要：Portable water filters are crucial to water purification for household or community-scale usage, and are particularly prominent in developing countries or remote areas without water treatment plants. However, a growing concern is that activated carbon can be a good support medium for microbial growth, eventually forming active biofilms. Herein, we report the preparation and functional validation of a new self-disinfecting carbon filter. The addition of an Ag/AgCl-Ru/RuO_2 mesh developed in this study does not require modifica-tion of current activated carbon products by any additional industrial process and maintains the adsorption capability of activated carbon for environmental pollutants. The in situ generation of reactive oxygen species (ROS), including H_2O_2, O~(?-)_2 or their combination which are responsible for the disinfection effect, offers an alternative functional module for activated carbon systems. Our system provides an alternative solution for overcoming a crucial limitation of current carbon filter systems: requirement of an external stimulus, such as light or electrical energy, for the formation of ROS. Thus, the above observations may prove to be the basis of a technology that allows self-disinfection of water within contact times for which conventional carbon filters are ineffective.
查看更多>>摘要：In this work, we illustrate the fabrication of binary gels via self-sorting assembly between β-cyclodextrin and the second gelators, which show significant transparency changes responsive to the solvent vapor and temperature. The mixing of β-cyclodextrin and clay minerals in the mixture of dimethylformamide and water produced opaque gels. After exposed to specific solvent environments, the light transmittance of opaque gels was greatly enhanced ascribed to the host-guest complexation between β-cyclodextrin and organic solvent vapors. Toluene, xylene, tetrahydrofuran, dioxane and pyridine aroused gel fiber to bulky crystal transformation, which also slightly enhanced the mechanical strength of the binary gels. In addition, the gelator could be expanded to organic gelator like folic acid. This work offers a feasible way to fabricate soft gel composites that show transparency changes responsive to solvent vapors.
查看更多>>摘要：The flotation separation of scheelite from fine calcite is difficult due to the larger specific surface area and higher activity with flotation collectors. The selectivity of caustic starch as the depressant is poor, due to the -OH functional group reacting with the similar Ca~(2+) active sites of scheelite and calcite. In this paper, a novel structure of Al-caustic starch is prepared by the reaction of Al~(3+) and caustic starch, which has a new functional group of -CH_2-O-Al~(2+). The Al-caustic starch is an effective depressant for the fine calcite particles, contributing to the efficient flotation separation of scheelite from the fine calcite particles. All the flotation kinetics of scheelite and fine calcite is first-order uniform distribution model, and the flotation rate of calcite decreases significantly after the treatment of Al-caustic starch. The zeta potential of Al-caustic starch is much higher than that of caustic starch, and Al-caustic starch can selectively change the surface charge of fine calcite, instead of scheelite. The X-ray photoelectron spectroscopy (XPS) spectrum of Al-caustic starch appears the peak of Al atom, which chem-isorb on the calcite surface and make the peak of characteristic atoms shift. Moreover, Al-caustic starch reacts with the anion of CO~(2-)_3 on fine calcite surface, instead of cation of Ca~(2+), which obviously improves the selective adsorption on mineral surface.
查看更多>>摘要：Biological macromolecular drugs usually have good efficacy and recognition performance. However, due to their large molecular weight and easy degradation/inactivation, general carriers are difficult to transport them into cell stably and safely. Here, a pH/redox dual-responsive microgel capsule was prepared for constructing a double-locked drug delivery system. Firstly, the pH-sensitive poly(ethyleneimine)-block-poly(2-(diisopropyla-mino ethylmethacry-late)-block-poly(ethyleneimine) triblock copolymers (PEI-PDPA-PEI) were synthesized for preparing polymer vesicles. The PEI layer was crosslinked by disulfide groups to finally obtain pH/redox dualresponsive microgel capsule, marked as P-VesicleGEL. Then, the P-VesicleGEL was used to encapsulate different types of drugs (doxorubicin hydrochloride, rhodamine, proteins, aptamer), and had a higher loading capacity than the corresponding polymer micelles for macromolecules. Compared with small molecules, P-VesicleGEL had much better "double-locked" function for macromolecules. I.e., only when the two "locks" were opened simul-taneously the release could be triggered. Furtherly, cell experiments had proved that the P-VesicleGEL had excellent biocompatibility and cell transfection ability. It could not only effectively identify normal and cancer cells, but also transport biological drugs that were difficult to enter into cells by themselves. The microgel capsule designed here is expected to be applied for the intracellular delivery/release of biological macromolecular drugs.
查看更多>>摘要：The aim of this study is to investigate the performance of mixed surfactants reverse microemulsion systems by adding different proportions of sodium dodecyl sulfate (SDS) to sodium bis (2-ethylhexyl) sulfosuccinate(AOT)/isooctane/water reverse microemulsions. The effects of solubilization water, conductivity and KCl ionic strength on the formation boundary and formation process of AOT/isooctane/water reverse microemulsion were inves-tigated by combining experiments with dissipative particle dynamics (DPD) simulations. The formation mech-anism is initially explored by mutual validation of experiments and simulations. This approach can help researchers to quickly infer structural changes and also reduce the cost of experimental development. Based on the performance of the AOT reverse microemulsion system, AOT-SDS reverse microemulsion system was pre-pared with the mass ratios of AOT: SDS of 9:1, 7:3, 5:5, 3:7, 1:9. The reverse microemulsion with AOT: SDS of 9:1 demonstrated the best characteristics in water solubilization and stability. By comparing the performance of two microemulsions to demonstrate that SDS changed the structure of AOT reverse microemulsion and its solubili-zation water volume and stability. Moreover, we believe that the AOT-SDS/isooctane/water microemulsion system is worthy to be developed by comparing similar mixed surfactant microemulsion systems.
查看更多>>摘要：A numerical study on the diffusiophoresis of a hydrophobic charged colloid driven by an imposed concentration gradient of an electrolyte is made. Our numerical model is based on the computation of Navier-Stokes-Nernst-Planck-Poisson equations. Diffusiophoresis of hydrophobic particles and size-based sorting has not been attempted before. The present numerical model elucidates the nonlinear effects on diffusiophoresis in a valence asymmetric electrolyte, which have been ignored in previous studies. The particle hydrophobicity, characterized by the slip length, modifies the ζ-potential and the Debye layer, which in turn creates a significant impact on the particle diffusiophoresis. An analytical solution, valid for a lower range of slip length and imposed concentration gradient is obtained under the thin Debye layer consideration, which compares well with the numerical solution for a thin Debye length when the slip length is a few tens of nanometer. We investigate the impact of slip length on the diffusiophoresis by considering different types of monovalent and valence asymmetric electrolytes. The surface hydrophobicity enhances the particle ζ-potential by reducing the shielding effect and the impact becomes stronger at a thinner Debye layer. For this, the mobility reversal manifests for a hydrophobic particle when the electrophoresis and chemiphoresis parts are competitive. Hydrophobicity enhances the mobility of the particle when electrophoresis and chemiphoreis are cooperative. The higher valence of the counterions of the electrolyte enhances the mobility for the moderate range of the Debye length by increasing the chemiphoresis part. The sizebased sorting of the particle by diffusiophoresis is analyzed. At a thinner Debye length the diffusiophoretic mobility of a hydrophobic particle exhibits a size dependency.
查看更多>>摘要：Migration of moisture and ions in C-S-H nanopores is restricted due to the prominence of interfacial effect and intermolecular forces. This paper provided a migration model of water and chloride ions considering ion cor-relation, dual interface slip and time-varying characteristics of Electrical Double Layer (EDL), which based on governing equations and boundary conditions of nano-flow as well as the hierarchical structure and transport mechanism of restricted liquids. In the paper, the wettability of the C-S-H surface was investigated by conducting contact angle experiments on the synthesized single-phase C-S-H, then the distribution characteristics of water and ions were described in combination with the properties of restricted liquids. By introducing slip length and velocity, the slip between solid-liquid interfaces and the slip between liquid layers near the wall were described. The time-varying properties of the double layer are described by introducing Einstein-Stokes equation and Modified Poisson-Boltzmann equation. Based on AFM, wedge coefficient was introduced into the model to characterize the pore morphology. The results show that the contribution ratio of slip and time-varying of EDL can reach about 70% and 20%, respectively and this phenomenon is more significant in smaller pore size. There are large differences in small and large pore sizes for the phenomena caused by different ion correlation strength conditions. Under strong ion correlation, the influence of water film slip is weakened by 8-10% due to the existence of strong adhesion between solid-liquid interface. The findings provided a systematic insight into the micro-and nanoscale flow.
查看更多>>摘要：Using biomass-derived materials for oil production is not a new concept but using them to stabilize foam via synergistic interactions is new for oil production. There is a lack of research and technology showing the advantage of biomass-derived nanomaterials at reservoir conditions for CO_2 Enhanced oil recovery processes. Cellulose nanocrystal (CNC) is an Alberta based wood-derived nanomaterial. In this work, we are testing the feasibility of CNC based CO_2 foam synergistically stabilized by CNC and surfactant. We first design a composition of CNC/surfactant for stable CO_2 foam on the concept of synergy between nanoparticles and surfactant. Then we evaluate the conformance control of CNC-enabled foam in dynamic tests and view how foam evolves over time using computed tomography imaging. Ultra-stable foam is achieved with surfactant concentration as low as 0.05 wt%. Foam potential in limiting the CO_2 pathways is shown and its conformance control ability is confirmed visually. This study demonstrates a cost-effective and simple way of surface modification by using a cationic surfactant via electrostatic interactions. Instead of bringing modified CNCs to the interface for the stabilization, the synergism between DTAB and native CNCs is exploited to obtain Pickering foams with superior stabilities. The results provide baseline information for other research on CNC based fluids for underground applications.
NSTL
Elsevier