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Gold (Au) and silver (Ag) nanoparticles (NPs) are covalently conjugated onto the surface of thiol‐functionalized block copolymer particles containing surfactant‐rich liquid crystalline cores. The resulting planet–satellite nanoconjugates display enhanced colloidal stability upon changes in solution pH or ionic strength and interfacial properties that result in the stabilization of oil‐in‐water emulsions. These biphasic systems are used as medium for catalyzed aerobic oxidation of benzyl alcohol to benzoic acid and the nanoconjugates display catalytic activity comparable to the single Ag and Au NPs in aqueous medium, with the advantage of an easier and more efficient separation of unreacted alcohol and product from reaction medium, making this the first report on interfacial gold‐ and silver‐catalyzed aerobic alcohol oxidation. These results, and the flexibility of the present approach, support the proposal of this methodology as a general platform for interfacial catalysis based on these novel nanomaterials. 相似文献
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Catherine P. Whitby Haley Scarborough Yung Ngothai 《Advanced Powder Technology》2017,28(11):2940-2946
We report on the formation of powder by drying oil-in-water emulsions stabilized by silanised silica nanoparticles. Drying was achieved by spraying fine droplets (up to a hundred micrometres in diameter) of the emulsions into a chamber of hot, flowing air. We show that the surfaces of droplets of the emulsions become enriched with nanoparticles as the water evaporates in the drying chamber. Controlling the relative amounts of oil and particles in the droplets being dried is the key to encapsulating the oil drops within the powder. Dried Pickering emulsions containing up to 40 wt% encapsulated oil that could be dispersed in water as drops of the same size as in the original emulsion were produced. 相似文献
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Naresh Yandrapalli Tom Robinson Markus Antonietti Baris Kumru 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(32)
Graphitic carbon nitride (g‐CN) has been utilized as a heterogeneous catalyst, but is usually not very well dispersible. The amphiphilic character of g‐CN can be altered by surface modifications of g‐CN nanopowders. Introducing hydrophilicity or hydrophobicity is a promising avenue for producing advanced emulsion systems. In this study, a special surface‐modified g‐CN is used to form stable Pickering emulsions. Using a PDMS‐based microfluidic device designed for stable production of both single and double emulsions, it is shown that surface‐modified g‐CNs allow the manufacture of unconventionally stable and precise Pickering emulsions. Shell thickness of the double emulsions is varied to emphasize the robustness of the device and also to demonstrate the extraordinary stabilization brought by the surface‐modified carbon nitride used in this study. Due to the electrostatic stabilization also in the oil phase, double emulsions are centered. Finally, when produced from polymerizable styrene, hollow polymer microparticles are formed with precise and tunable sizes, where g‐CN is utilized as the only stabilizer and photoinitiator. 相似文献
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Kang Hee Ku Jie Li Kosuke Yoshinaga Timothy M. Swager 《Advanced materials (Deerfield Beach, Fla.)》2019,31(51)
Dynamically reconfigurable oil‐in‐water (o/w) Pickering emulsions are developed, wherein the assembly of particles (i.e., platinum‐on‐carbon and iron‐on‐carbon particles) can be actively controlled by adjusting interfacial tensions. A balanced adsorption of particles and surfactants at the o/w interface allows for the creation of inhomogeneity of the particle distribution on the emulsion surface. Complex Pickering emulsions with highly controllable and reconfigurable morphologies are produced in a single step by exploiting the temperature‐sensitive miscibility of hydrocarbon and fluorocarbon liquids. Dynamic adsorption/desorption of (polymer) surfactants afford both shape and configuration transitions of multiple Pickering emulsions and encapsulated core/shell structured can be transformed into a Janus configuration. Finally, to demonstrate the intrinsic catalytic or magnetic properties of the particles provided by carbon bound Pt and Fe nanoparticles, two different systems are investigated. Specifically, the creation of a bimetallic microcapsule with controlled payload release and precise modulation of translational and rotational motions of magnetic emulsions are demonstrated, suggesting potential applications for sensing and smart payload delivery. 相似文献
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Anna W. Kuziel Karolina Z. Milowska Pak-Lee Chau Slawomir Boncel Krzysztof K. Koziol Noorhana Yahya Mike C. Payne 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2000608
The fundamental colloidal properties of pristine graphene flakes remain incompletely understood, with conflicting reports about their chemical character, hindering potential applications that could exploit the extraordinary electronic, thermal, and mechanical properties of graphene. Here, the true amphipathic nature of pristine graphene flakes is demonstrated through wet-chemistry testing, optical microscopy, electron microscopy, and density functional theory, molecular dynamics, and Monte Carlo calculations, and it is shown how this fact paves the way for the formation of ultrastable water/oil emulsions. In contrast to commonly used graphene oxide flakes, pristine graphene flakes possess well-defined hydrophobic and hydrophilic regions: the basal plane and edges, respectively, the interplay of which allows small flakes to be utilized as stabilizers with an amphipathic strength that depends on the edge-to-surface ratio. The interactions between flakes can be also controlled by varying the oil-to-water ratio. In addition, it is predicted that graphene flakes can be efficiently used as a new-generation stabilizer that is active under high pressure, high temperature, and in saline solutions, greatly enhancing the efficiency and functionality of applications based on this material. 相似文献
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Jong Bin Kim Su Yeon Lee Nam Gi Min Seung Yeol Lee Shin-Hyun Kim 《Advanced materials (Deerfield Beach, Fla.)》2020,32(26):2001384
Metal nanostructures have been created in a film format to develop unique plasmonic properties. Here, well-defined metal nanostructures are designed on the surface of microspheres to provide plasmonic microgranules. As conventional techniques are inadequate for nanofabrication on spherical surfaces, photocurable emulsion drops with a regular array of silica particles are employed at the interface to create periodic nanostructures. The silica particles, originating from the dispersed phase, fully cover the interface by forming a non-close-packed hexagonal array after drop generation, and slowly protrude to the continuous phase during aging while their interparticle separation decreases. Therefore, hexagonal arrays of spherical dimples with controlled geometry and separation are created on the surface of microspheres by photocuring the drops and removing the particles. Directional deposition of either aluminum or gold results in a continuous film with a hexagonal array of holes on the outermost surface and isolated curved disks in dimples, which renders the hemisphere of microspheres plasmonically colored. The resonant wavelength is controlled by adjusting the aging time, metal thickness, and size of silica particles, providing various plasmonic colors. This granular format of the plasmonic Janus microspheres will open a new avenue of optical applications including active color pixels, optical barcodes, and microsensors. 相似文献
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With their hierarchical structures and the substantial surface areas, hollow particles have gained immense research interest in biomedical applications. For scalable fabrications, emulsion‐based approaches have emerged as facile and versatile strategies. Here, the recent achievements in this field are unfolded via an “emulsion particulate strategy,” which addresses the inherent relationship between the process control and the bioactive structures. As such, the interior architectures are manipulated by harnessing the intermediate state during the emulsion revolution (intrinsic strategy), whereas the external structures are dictated by tailoring the building blocks and solidification procedures of the Pickering emulsion (extrinsic strategy). Through integration of the intrinsic and extrinsic emulsion particulate strategy, multifunctional hollow particles demonstrate marked momentum for label‐free multiplex detections, stimuli‐responsive therapies, and stem cell therapies. 相似文献
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Zimmermann C Feldmann C Wanner M Gerthsen D 《Small (Weinheim an der Bergstrasse, Germany)》2007,3(8):1347-1349
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Wu C Bai S Ansorge-Schumacher MB Wang D 《Advanced materials (Deerfield Beach, Fla.)》2011,23(47):5694-5699
Encapsulation of enzymes in Pickering emulsions results in a large interfacial area of the enzyme-containing aqueous phase for biocatalysis in organic media. This immobilization technique minimizes enzyme inactivation through stabilizing immiscible liquids by particles, facilitates separation processes, and significantly increases catalytic performance of both stable and vulnerable enzymes. Thus, a broad technical applicability can be envisioned. 相似文献
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Silica nanoparticle-armored polyaniline microspheres (SNAPMs) were synthesized in a Pickering emulsion for the first time. The products were characterized by SEM, XRD and FTIR. The FTIR results showed that the silica nanoparticles were attached to the surfaces of the polyaniline microspheres by a hydrogen bonding action. The SEM results showed that the amount of the silica nanoparticles added in the emulsion had a distinct effect on the morphology and size of the SNAPMs. A mechanism for the formation of the SNAPMs was discussed. The route reported here may be used for the preparation of other composite nanostructures. 相似文献
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《Advanced Powder Technology》2021,32(10):3672-3688
In this work, Z-scheme Ag2S/Bi2O3 composites were fabricated through the precipitation of Ag2S nanoplates on the surface of Bi2O3 microrods. Consequently, Au nanoparticles were selectively deposited on the Ag2S nanoplates surface to obtain.Au-Ag2S/Bi2O3 composites using near-infrared light photodeposition method. The characterization results indicate that the Ag2S nanoplates were uniformly anchored on Bi2O3 surface, and Au nanoparticles were highly dispersed on the surface of Ag2S nanoplate instead of Bi2O3. Acid orange 7 (AO7), Rhodamine B (RhB) and Cr(VI) were chosen as model reactant for the evaluation of photocatalytic degradation and reduction activity of the products under simulated sunlight irradiation. After the decoration of Ag2S nanoplates, the photocatalytic activity of Ag2S/Bi2O3 is much higher than that of bare Bi2O3, and the optimal catalytic efficiency is achieved by 12 %Ag2S/Bi2O3 sample. More importantly, the photocatalytic activity of 12 %Ag2S/Bi2O3 sample can be further enhanced by the selective decoration Au nanoparticles on the Ag2S nanoplates. Among the ternary composites, 2Au-12 %Ag2S/Bi2O3 sample with the Au content of 2% exhibits highest catalytic efficiency for 60 min (AO7: 96%; RhB: 56%; Cr(VI): 65%). The possible mechanism for the improvement of the photocatalytic activity of Bi2O3 by Ag2S and Au decoration was proposed. 相似文献
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Pickering emulsions are stabilized by solid particles assembled at an immiscible liquid–liquid interface. In this work, the use of such emulsions to prepare semiconductor Janus particles through UV‐irradiation is explored. Titanium dioxide particles that are prefunctionalized with an alkylsilane or a fluoroalkylsilane are employed to obtain wax‐in‐water emulsion droplets, which consist of the particles partially embedded in the wax core. Different emulsion formation mechanisms are discussed. The emulsified wax droplets are then subjected to ultraviolet irradiation, which photocatalytically degrades the silanes on the exposed portion of the particle surfaces, leading to Janus particles containing partial silane coatings. The particles are finally recovered through dissolution of wax. The Janus particles, which have contrasting wettabilities over their surface, are characterized based on self‐assembly behavior and bulk wetting performance in a compact film, as compared with nonfunctionalized and fully‐functionalized homogeneous particles. Three different types of Janus particles are created and their characters are explained using the concept of the Janus balance. The method has the potential to produce large scale yields in a relatively short time, and can be potentially applied to other semiconductor particles for the generation of Janus particles. 相似文献
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Weizheng Zhou Gangsheng Tong Dali Wang Bangshang Zhu Yu Ren Michael Butler Eddie Pelan Deyue Yan Xinyuan Zhu Simeon D. Stoyanov 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(13):1797-1805
Hierarchical porous structures are ubiquitous in biological organisms and inorganic systems. Although such structures have been replicated, designed, and fabricated, they are often inferior to naturally occurring analogues. Apart from the complexity and multiple functionalities developed by the biological systems, the controllable and scalable production of hierarchically porous structures and building blocks remains a technological challenge. Herein, a facile and scalable approach is developed to fabricate hierarchical hollow spheres with integrated micro‐, meso‐, and macropores ranging from 1 nm to 100 μm (spanning five orders of magnitude). (Macro)molecules, micro‐rods (which play a key role for the creation of robust capsules), and emulsion droplets have been successfully employed as multiple length scale templates, allowing the creation of hierarchical porous macrospheres. Thanks to their specific mechanical strength, these hierarchical porous spheres could be incorporated and assembled as higher level building blocks in various novel materials. 相似文献
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Céline. A. S. Burel Ahmed Alsayed Ludivine Malassis Christopher B. Murray Bertrand Donnio Rémi Dreyfus 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(39)
Efficiently detecting mechanical deformations within materials is critical in a wide range of devices, from micro‐electromechanical systems to larger structures in the aerospace industry. This communication reports the fabrication of new mechanochromic micrometer‐size capsules enabling the detection of strains. These microcapsules are synthesized using an emulsification approach. They are made of densely packed gold nanoparticles embedded in a spherical silica crust. Billions of these composite spherical microcapsules are fabricated in a single batch. Each microcapsule is an opto‐mechanosensor by itself, and can easily be recovered and incorporated into polymer films. When the films are stretched, the microcapsules are deformed into elongated ellipsoidal shapes and the distance between the Au NPs embedded in their shells concomitantly increases. As the extinction of Au NPs depends on the separation between the Au NPs, microcapsules exhibit different colors when they are elongated. These novel sensitive microcapsules can be used to detect and measure strain in polymer films by outputting color information. 相似文献
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