Evaluation of Pickering emulsions stabilized with nano-cellulose and nano-chitin treated with deep eutectic solvent

Developing bio-friendly and degradable Pickering emulsifiers as surfactants to replace traditional surfactants with bio-toxicity is imperative in the food, coating, cosmetics, and pharmaceutical industries. Nanocellulose and chitin can be used directly as an emulsifier to prepare Pickering o/w emulsions. As the concentration of nanoparticles increases, the stability of the emulsion also increases, and an overly large nanoparticle aspect ratio is not conducive to the stabilization of the emulsion. In comparison, nanocellulose-prepared Pickering emulsion has improved stability. Of these, nanocellulose prepared by DES with a molar ratio of 3:1 to LA:CC has been shown to have the best stability when used to equilibrate the oil/water mass ratio of 2/8. The Zeta potential is −38.4 mV, and the size of the droplets is the most uniform. With a mean droplet diameter of 770 nm. This study had certain research significance and reference value for the development of bio-friendly surfactants.     

TiO2纳米颗粒稳定的Pickering乳液用作防晒乳成分研究

采用烷基化改性的TiO_2纳米颗粒为稳定剂,化妆品级白油为油相,黄芪水溶液为水相,制备了一种载药Pickering乳液。利用TEM、接触角测试仪和光学显微镜对TiO_2纳米颗粒及载药Pickering乳液进行了表征。结果表明,该纳米颗粒分散性良好、尺寸均匀,具备良好的稳定乳液能力;通过紫外吸收测试,控制释放药物和清洗对照实验,表明该载药Pickering乳液具有较高的防晒效果和随光照时间控制释放药物以及易于从皮肤表面清洗的特性。     

细菌纤维素纳米晶稳定液体石蜡Pickering乳液的制备

采用生物法合成了高纯度的细菌纤维素(BC),通过浓硫酸水解制得细菌纤维素纳米晶(BCN)。以液体石蜡为油相,BCN为固体乳化剂,在超声作用下制得O/W型Pickering乳液。通过SEM,TEM,FT-IR,XRD,接触角测量仪及激光粒度和Zeta电位分析仪对BC及BCN进行了表征。考察了BCN质量浓度、水相p H和离子强度对Pickering乳液稳定性的影响。结果表明,BC在浓硫酸水解过程中发生了氧化反应,其水解主要发生在无定型区,使所得BCN的结晶指数高达97%。BCN悬浮液的粒径和Zeta电位值分别为462.5 nm和-40.8 m V,其三相接触角为95.7°,具有良好的乳化性能。在超声乳化作用下制得的乳液粒径大小为8.6~17.3μm。通过调控水相p H能够改变BCN表面电荷密度,从而改变乳液的稳定性,随着水相p H的增大,乳液相体积分数增大,乳液稳定性增强。随着Na Cl浓度的增大,乳液的稳定性降低,乳液相体积分数减小。此外,SEM的观测结果表明,BCN在稳定Pickering乳液过程中呈现纤维线条和聚集体颗粒2种形态。     

二氧化硅空心球的制备及研究

在乙醇/水的混合溶液中,采用聚乙烯吡咯烷酮（PVP）为分散剂,偶氮二异丁腈（AIBN）为引发剂,通过分散聚合法制备出聚苯乙烯（PS）微球。然后以微球为模板,PS粒子作为核,SiO_2作为壳,在600℃时经过热分解得到SiO_2空心球。通过热分析仪、扫描电子显微镜对制得的空心球进行了表征和分析,并讨论其影响因素。     

双重Pickering乳液法制备聚丙烯酰胺多孔微球及应用

采用亲水性气相二氧化硅N20和疏水性气相二氧化硅H30复配表面活性剂制备O/W/O型双重乳液,以此为模板,聚合中间相,挥发内相制备聚丙烯酰胺(PAM)多孔微球,并用于染料分子亚甲基蓝的吸附。结果表明：乳液显微镜照片显示水油比对双重乳液的形成有很大的影响,当水油比(O₁/W)/O₂为(1/2)/2时,可得到稳定的双重乳液;扫描电镜(SEM)照片显示PAM多孔微球基本呈球形,但粒径不均匀,球体表面粗糙,内部为空心结构;激光粒度仪(DLS)结果表明PAM微球平均粒径为356nm,多分散系数(PDI)为0.718,比表面积为230m²/g,粒径分布宽;在吸附温度35℃、吸附时间5min时对亚甲基蓝的吸附率为98.89%,最大吸附率超过99%,在吸附速率和吸附率上均优于传统PAM吸附剂,本研究为染料废水的处理提供了新方法。     

pH-triggered phase inversion and separation of hydrophobised bacterial cellulose stabilised Pickering emulsions

The pH-triggered transitional phase behaviour of Pickering emulsions stabilised by hydrophobised bacterial cellulose (BC) is reported in this work. Neat BC was esterified with acetic (C₂–), hexanoic (C₆–) and dodecanoic (C₁₂–) acids, respectively. We observed that C₆– and C₁₂–BC stabilised emulsions exhibited a pH-triggered reversible transitional phase separation. Water-in-toluene emulsions containing of 60 vol.% dispersed phase stabilised by C₆– and C₁₂–BC were produced at pH 5. Lowering the pH of the aqueous phase to 1 did not affect the emulsion type. Increasing the pH to 14, however, caused the emulsions to phase separate. This phase separation was caused by electrostatic repulsion between modified BC due to dissociable acidic surface groups at high pH, which lowered the surface coverage of the water droplets by modified BC. When the pH was re-adjusted to 1 again, w/o emulsions re-formed for C₆– and C₁₂–BC stabilised emulsions. C₂–BC stabilised emulsions, on the other hand, underwent an irreversible pH-triggered transitional phase separation and inversion. This difference in phase behaviour between C₂–BC and C₆–/C₁₂–BC was attributed to the hydrolysis of the ester bonds of C₂–BC at high pH. This hypothesis is in good agreement with the measured degree of surface substitution (DSS) of modified BC after the pH-triggered experiments. The DSS of C₂–BC decreased by 20% whilst the DSS remained constant for C₆– and C₁₂–BC.     

湿法球磨改性蒙脱土及其稳定液体石蜡/水Pickering乳液的制备

以钠基蒙脱土(Na-MMT)为原料,采用湿法球磨法制备双十二烷基二甲基溴化铵(DDAB)插层的改性蒙脱土(DDA-MMT),并在超声作用下乳化液体石蜡制得O/W型Pickering乳液。通过XRD、TEM、FT-IR、接触角测量仪和Zeta电位及激光粒度仪对DDA-MMT进行了表征。考察了DDA-MMT颗粒质量浓度、水相p H和离子强度对Pickering乳液稳定性的影响。实验结果表明,在球磨机械力作用下DDAB成功插入Na-MMT的片层间,使Na-MMT的平均粒径、Zeta电位和三相接触角分别由910.7 nm,-26.8 m V和121.7°变为603.8 nm,38.3 m V和86.9°。与Na-MMT颗粒相比,DDA-MMT颗粒更容易在油/水界面间聚集而具有更好的乳化稳定性。随着DDA-MMT颗粒质量浓度的增大,Pickering乳液液滴粒径减小,乳液体积分数增大,稳定性增强。当水相p H=6.26~8.36,c(Na Cl)=20 mmol/L时,由DDA-MMT颗粒乳化制备的Pickering乳液稳定性较佳。     

Multihollow nanocomposite microspheres with tunable pore structures by templating Pickering double emulsions

Micrometer-sized dual nanocomposite polymer microspheres with tunable pore structures were fabricated using a simple and straightforward method based on Pickering double emulsions. First, a primary water-in-styrene (oil) emulsion (w₁/o) was prepared using the hydrophobic silica nanoparticles as a particulate emulsifier without any molecular surfactants. Then, a water-in-styrene-in-water (w₁/o/w₂) Pickering emulsion was produced by the emulsification of the primary w₁/o emulsion into water using Fe₃O₄ nanoparticles as external emulsifier. The big styrene droplets containing small water droplets were polymerized after the formation of the double emulsions. Nanocomposite polystyrene microspheres with a multihollow structure were obtained and their morphological structures were studied by scanning electron microscopy (SEM). The pore structure of the microspheres could be tuned by the volume ratio of the internal water phase to the medium oil phase (w₁:o) of the primary emulsions. With increasing w₁:o from 1:8 to 4:1, the amount of the pores in one microsphere increased gradually and the pore structures changed from close to interconnected. The resulting multihollow microspheres had a responsive ability to magnetic stimulus due to the existence of Fe₃O₄ nanoparticles. This kind of multihollow hybrid polymer microspheres is expected to have a wide potential application in materials science and biotechnology.     

Pickering乳液研究进展

Pickering乳化剂是指用固体颗粒代替传统的化学乳化剂,固体颗粒在分散相液滴表面形成一层薄膜阻止了液滴之间的聚集,在造纸、乳液聚合、化妆品、药物缓释和制备功能高分子领域具有应用前景。本文从Pickering乳化剂的作用机理、乳化稳定因素、相转化以及应用几个方面进行总结。     

Nano-sized carbon hollow spheres for abatement of ethylene

In this paper, the ethylene adsorption capacities of the nano-sized carbon hollow spheres (CNB) and active carbon (AC), the Pd (PdCl₂) impregnated CNB or AC (Pd/CNB, Pd/AC) and heat treatment under various conditions, were studied at different ethylene concentrations from 64 to 1060 ppm. The results indicated that AC had a good ethylene adsorption capacity at high ethylene concentration. Pd impregnation decreased the ethylene adsorption capacity of AC. Heat treatment and H₂ activation could increase the ethylene adsorption capacity, but also lowered than AC itself. CNB had lower ethylene adsorption capacity than AC, but heat treatment and H₂ activation could increase its ethylene adsorption capacity markedly. With activating condition from heat treatment in N₂ at 300 °C to activation in H₂/N₂ at 100 °C, to activation in H₂ at 200 °C, and to activation in H₂ at 300 °C, the ethylene adsorption capacity of Pd/CNB was increased regularly. At low ethylene concentration, viz., 64 ppm, the ethylene adsorption quantities (q _a) by Pd/CNB activated in H₂ at 200 or 300 °C were higher than any other adsorbents. So, activated in H₂ atmosphere at higher than 100 °C, Pd/CNB is particularly advantaged for adsorbing low concentration of ethylene. Amongst all the adsorbents used, Pd/CNB activated in H₂ atmosphere at 300 °C for 2 h has the highest ethylene adsorption capacity at lower concentration than 125 ppm. In addition, all the CNB, Pd/CNB, AC, and Pd/AC samples can be easily regenerated in airflow for more than 3 h.     

Optical properties of colloidal crystalline arrays composed of hollow polystyrene spheres

We have evaluated the optical properties of close‐packed and non close‐packed colloidal crystalline arrays made of hollow polystyrene spheres. Close‐packed colloidal crystalline arrays were fabricated by simple evaporation of dispersions, whereas nonclose‐packed colloidal crystalline arrays were fabricated by exploiting electrostatic interactions between the spheres in aqueous dispersion. Optical properties of the arrays were estimated from angle‐resolved reflection spectra. The Bragg diffraction peak of the colloidal crystalline array made of hollow spheres was of shorter wavelength than in the case of solid spheres, not only for the close‐packed array but also for the nonclose‐packed array. These shifts were caused by a decrease in the effective refractive index n_eff with decreasing particle refractive index. We have found that this relationship could be explained by the simple equation n_eff = n_particle?+ n_solvent (1 ? ?), where ? is the volume fraction of the particles, for both close‐packed and non close‐packed arrays. The current work suggests new possibilities for the creation of advanced colloidal crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2364–2368, 2007     

Template synthesis of composite hollow spheres using sulfonated polystyrene hollow spheres

In this paper, we propose a general template synthesis approach towards composite hollow spheres using sulfonated polystyrene gel hollow spheres. The gel hollow spheres are highly crosslinked to well preserve the spherical contour during template synthesis. It is important that the gel shell is infiltrative to many species to allow their further growth therein by specific interaction. The grown materials are well distributed thorough the whole shell forming composite shells. This method is general, which is proved by the growth of many representative materials for example metal Pd nanoparticles, magnetite Fe₃O₄ nanocrystallites, conducting polyaniline, and inorganic titania and silica. It is found that mesoporous inorganic shells are obtained after the template gel is calcined. This concept can be applied to other gel shells and grown materials expecting a new family of composite hollow spheres.     

智能响应型Pickering乳液的制备及在物质分离中的应用进展

Pickering乳液是指由微纳米固体粒子代替传统表面活性剂作为乳化剂而稳定的乳液,具有较强的稳定性和超高油/水界面,能够为多相界面反应和物质传输提供高效稳定的场所。Pickering乳液的乳滴结构和性质与固体颗粒的尺寸形貌及表面性质密不可分,通过调控固体颗粒本身或表面的性质可以赋予Pickering乳液特定的响应性功能,拓宽其应用领域。本文对近年来不同响应型（磁性、CO₂、pH、光、温度等响应型）的Pickering乳液的主要研究成果进行了综述,重点介绍了Pickering乳液的稳定性原理、响应型Pickering乳液的制备方法和结构调控策略,以及近年来Pickering乳液在物质分离提取中的应用研究进展,最后对智能响应型Pickering乳液应用研究的发展趋势进行了展望。     

Nanostructured hollow spheres of hydroxyapatite: preparation and potential application in drug delivery

A solvothermal method has been successfully used to prepare nanostructured hydroxyapatite (HA) hollow spheres with average diameters of about 500 nm and shell thicknesses of about 100 nm in a glycerin/water mixed solvent. Transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM) images show that the shells of the HA hollow spheres are actually composed of nanosheets with thicknesses of about 10 nm. By tuning the glycerin/water volume ratio, two other kinds of HA solid spheres with average diameters of about 6 or 20 μm were assembled from nanoflakes. The properties of the different kinds of spheres as drug delivery carriers were evaluated. Ibuprofen (IBU) was chosen as the model drug to load into the HA samples. The nanostructured HA samples showed a slow and sustained release of IBU. The HA hollow spheres exhibited a higher drug loading capacity and more favorable release properties than the HA solid spheres and thus are very promising for controlled drug release applications.     

The effect of hydrodynamic parameters on the production of Pickering emulsions in a baffled stirred tank

Pickering emulsions are potential industrial scale alternatives to surfactant-based emulsions. The stability of Pickering emulsions depends on the physicochemical nature of the liquid–particle interface and the hydrodynamic conditions of the production process. This article investigates the effect of hydrodynamic conditions on the drop size of concentrated Pickering emulsions in baffled stirred tanks. Oil in water emulsions composed of silicon oil, water, and hydrophilic glass beads as stabilizing particles were produced. Two impellers were used at different sizes: Rushton turbine (RT) and pitched blade turbine. The effects of power per mass, Reynolds number, tip speed, and Weber number on the droplet sizes were studied. The energy dissipated around the impeller and the size of the impeller high shear zone were found to be critical to the emulsion droplet sizes. The breakup and droplet-particle contact mechanism of the RT was found to be more favorable for the production of the Pickering emulsions.     

Characteristics of Stable Pickering Emulsions under Process Conditions

Emulsions stabilized by solid particles are so called Pickering emulsions which are characterized by their high stability against coalescence. This type of emulsion can be used for a lot of applications. Very little is known about how reaction conditions affect their properties. In this study the influence of important reaction conditions like shear stress, pressure, temperature, and the influence of synthesis gas on Pickering emulsions is investigated. It is shown that the emulsions remain stable in terms of coalescence in a broad range of the reaction conditions and are suitable as reaction media for industrial processes and for a reaction optimization with a subsequent separation step.     

Carbonized thiourea formaldehyde resin blending polypyrrole hollow spheres composites with improved supercapacitor performances as electrodes

Thiourea formaldehyde resin has been condensation-polymerized in the polypyrrole hollow spheres suspension to obtain TF/PPy. Then, TF/PPy has been carbonized at 750 °C to acquire CTF/PPy composites. Scanning electron microscope and transmission electron microscope images were used to observe the morphology of the samples, TGA, XRD, Raman, XPS, and BET were used to analyze the structure of the materials. The results show PPy was blended with the TF resin, and the obtained CTF/PPy exhibited improved supercapacitive performances compared with CTF. The specific capacitance of CTF/PPy is 226.8 F g⁻¹ at the current density of 1 A g⁻¹ according to GCD curves, much higher than that of CTF. More interestingly, the cycling retention of CTF/PPy electrode at the current density of 10 A g⁻¹ is up to 120.2% after 10 000 cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47816.     

Effect of dispersed phase feed time on the droplet size of Pickering emulsions produced in a stirred tank

The aim of this study was to investigate the effect of feed time of the oil phase on the average droplet size of Pickering emulsions produced in stirred tanks. Three types of impellers were tested: RT, up-pumping PBT (PBTU), and down-pumping PBT (PBTD). All the impellers were tested at two sizes, T/3 and T/2. All configurations were compared at constant tip speed, power per mass, and impeller Reynolds number. The droplet diameters were measured in Mastersizer® 3,000 (Malvern). The results showed that an increase in feed time causes a reduction in the average droplet size. At lower impeller speeds and higher feed times, the effect is more pronounced. It was found that some other geometric parameters also have an impact on the average droplet size.     

Effect of sintering temperature on the characteristics of ceramic hollow spheres produced by sacrificial template technique

Ceramic hollow spheres were produced by a sacrificial template technique with subsequent sintering under temperatures ranging from 1100 °C to 1250 °C. The effect of the sintering temperature on the structure of the ceramic hollow spheres was investigated by optical and scanning electron microscopy, and a gas adsorption method. The results show that the structure of the ceramic hollow spheres can be controlled, with the retention of the hollow spherical shape, by variation of the sintering temperature. Increase of the sintering temperature from 1100 °C to 1250 °C decreased the outer diameter of the ceramic hollow spheres by 14 percent, the shell thickness by 18 percent, and the void area ratio of the shell surface by 9.2 times; both of the specific surface area and the total pore volume of ceramic hollow spheres decreased by 60 percent.     

A TiO2 modified whisker mullite hollow fiber ceramic membrane for high-efficiency oil/water emulsions separation

Design and preparation of membranes with ultrahigh separation performance and antifouling property for oil-in-water (O/W) emulsions remains challenging. In this study, a high flux mullite/TiO₂ ceramic composite membrane was prepared via multi-precipitation of TiO₂ on a whisker mullite hollow fiber support synthesized by combining phase inversion and high-temperature sintering techniques. The results showed that the generated whisker mullite structure improved the permeation flux, and the micro-nano structured TiO₂ functional layer endowed the membrane surface with superhydrophility and stability. The retention of the optimal composite membrane (M20T13) that was soaked in the titanium solution 20 times for 13 min each time for the O/W emulsions like n-hexane, toluene and engine oil maintained over 98 %, and the flux after 6 h filtration was 668.34 L·m⁻²·h⁻¹, 487.25 L·m⁻²·h⁻¹ and 258.66 L·m⁻²·h⁻¹, respectively, much higher than that of the optimal substrate (F3A1, mass ratio of fly ash: Al₂O₃ = 3:1). Moreover, the flux recovery rate of M20T13 was much higher than that of F3A1 after chemical backwashing. This work manifests great potential in O/W treatment fields.