The ability to design and assemble three-dimensional structures from colloidal particles is limited by the absence of specific directional bonds. As a result, complex or low-coordination structures, ...common in atomic and molecular systems, are rare in the colloidal domain. Here we demonstrate a general method for creating the colloidal analogues of atoms with valence: colloidal particles with chemically distinct surface patches that imitate hybridized atomic orbitals, including sp, sp(2), sp(3), sp(3)d, sp(3)d(2) and sp(3)d(3). Functionalized with DNA with single-stranded sticky ends, patches on different particles can form highly directional bonds through programmable, specific and reversible DNA hybridization. These features allow the particles to self-assemble into 'colloidal molecules' with triangular, tetrahedral and other bonding symmetries, and should also give access to a rich variety of new microstructured colloidal materials.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The fluidity of aqueous electrolytes and undesired H2 evolution reaction (HER) can cause severe interfacial turbulence in aqueous Zn metal batteries (ZMBs) at deep cycling with high capacities and ...current densities, which would further perturb ion flux and aggravate Zn dendrite growth. In this study, a colloid‐polymer electrolyte (CPE) with special colloidal phase and suppressed HER is designed to diminish interfacial turbulence and boost deep Zn electrochemistry. Density functional theory calculations confirm that the quantitative migratory barriers of Zn2+ along the transport pathway in CPE demonstrate much smaller fluctuations compared with normal aqueous electrolyte, indicating that CPE can effectively diminish interfacial disturbance. Benefitting from this, the Zn2+ ion flux can be homogenized and deposited evenly on the electrode, which is confirmed by finite element simulation and in situ Raman measurements. Consequently, CPE enables stable operation of Zn//Cu cells even with high capacity (up to 20 mAh cm−2) and current density (up to 100 mA cm−2) and Zn//Na5V12O32 full‐cell with N/P ratio as low as 1 (i.e., 100% Zn utilization). It is believed that this strategy opens a brand‐new avenue based on CPE toward boosting deep‐cycling electrochemistry in ZMBs and even other aqueous energy‐storage applications.
In this study, a new design of colloid‐polymer electrolyte (CPE) for use in Zn metal batteries is proposed to diminish interfacial disturbance and realize stable Zn2+ environment at deep cycling. The efficacies of the designed CPE are determined with a combination of density functional theory, finite element simulation, in situ Raman measurements, and electrochemical tests for Zn‐based cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Fluid flow is ubiquitous in many environments that form habitats for microorganisms. Therefore, it is not surprising that both biological and artificial microswimmers show responses to flows that are ...determined by the interplay of chemical and physical factors. In particular, to deepen the understanding of how different systems respond to flows, it is crucial to comprehend the influence played by swimming pattern. The tendency of organisms to navigate up or down the flow is termed rheotaxis. Early theoretical studies predicted a positive rheotactic response for puller-type spherical Janus micromotors. However, recent experimental studies have focused on pusher-type Janus particles, finding that they exhibit cross-stream migration in externally applied flows. To study the response to the flow of swimmers with a qualitatively different flow pattern, we introduce Cu@SiO2 micromotors that swim toward their catalytic cap. On the basis of experimental observations, and supported by flow field calculations using a model for self-electrophoresis, we hypothesize that they behave effectively as a puller-type system. We investigate the effect of externally imposed flow on these spherically symmetrical Cu@SiO2 active Janus colloids, and we indeed observe a steady upstream directional response. Through a simple squirmer model for a puller, we recover the major experimental observations. Additionally, the model predicts a “jumping” behavior for puller-type micromotors at high flow speeds. Performing additional experiments at high flow speeds, we capture this phenomenon, in which the particles “roll” with their swimming axes aligned to the shear plane, in addition to being dragged downstream by the fluid flow.
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The preparation of particles with non-spherical shapes is a challenging endeavor, often requiring a significant ingenuity, complex experimental procedures and difficulties to obtain ...reproducible results. In this work we prove that monodisperse non-spherical polymer particles possessing asymmetric Janus structure can be easily produced by using an activated swelling method in combination with a control of the rate of free radical polymerization through the addition of the inhibitors 4-methoxyphenol (MEHQ) and O2. Monodisperse non cross-linked polystyrene particles, used as seeds, are activated by the addition of an initiator, which promotes their swelling ability, and then swollen with a monomers mixture (methyl methacrylate, glycidyl methacrylate and ethylene glycol dimethacrylate), before being polymerized in presence of both MEHQ and O2. Our results show that only when both MEHQ and O2 are present during the course of the polymerization, the particles shape can be controlled, from spherical to asymmetrical. A variety of particles shapes can be obtained, ranging from dimpled spheres, flattened spheres and Janus particles by varying the swelling ratio, always with excellent monodispersity and reproducibility. Finally, to provide even more complex functionalities to these non-spherical polymer particles, iron oxide nanocrystals were grown within the polymer matrix resulting in superparamagnetic particles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Semiconductors are at the basis of electronics. Up to now, most devices that contain semiconductors use materials obtained from a top down approach with semiconductors grown by molecular beam epitaxy ...or chemical vapor deposition. Colloidal semiconductor nanoparticles have been synthesized for more than 30 years now, and their synthesis is becoming mature enough that these nanoparticles have started to be incorporated into devices. An important development that recently took place in the field of colloidal quantum dots is the synthesis of two-dimensional (2D) semiconductor nanoplatelets that appear as free-standing nanosheets. These 2D colloidal systems are the newborn in the family of shaped-controlled nanoparticles that started with spheres, was extended with rods and wires, continued with tetrapods, and now ends with platelets. From a physical point of view, these objects bring 1D-confined particles into the colloidal family. It is a notable addition, since these platelets can have a thickness that is controlled with atomic precision, so that no inhomogeneous broadening is observed. Because they have two large free interfaces, mirror charges play an important role, and the binding energy of the exciton is extremely large. These two effects almost perfectly compensate each other, it results in particles with unique spectroscopic properties such as fast fluorescent lifetimes and extreme color purity (narrow full width at half-maximum of their emission spectra). These nanoplatelets with extremely large confinement but very simple and well-defined chemistry are model systems to check and further develop, notably with the incorporation in the models of the organic/inorganic interface, various theoretical approaches used for colloidal particles. From a chemical point of view, these colloidal particles are a model system to study the role of ligands since they have precisely defined facets. In addition, the synthesis of these highly anisotropic objects triggered new research to understand at a mechanistic level how this strong anisotropy could be generated. Luckily, some of the chemical know-how built with the spherical and rod-shaped particles is being transferred, with some adaptation, to 2D systems, so that 2D core/shell and core/crown heterostructures have recently been introduced. These objects are very interesting because they suggest that multiple quantum wells could be grown in solution. From the application point of view, 2D colloidal nanoplatelets offer interesting perspectives when color purity, charge conductivity, or field tunable absorption are required. In this Account, we review the chemical synthesis, the physical properties, and the applications of colloidal semiconductor nanoplatelets with an emphasis on the zinc-blende nanoplatelets that were developed more specifically in our group.
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Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, ...characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size‐ and shape‐dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid‐chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state‐of‐the‐art morphology control in noble metal nanoparticles.
Noble metal nanoparticles with an impressive range of morphologies, such as rods, wires, stars, boxes, etc. can be produced by a colloid‐chemical approach (see figure). This article reviews the recent progress in the colloid‐chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt). The article focuses on various factors that influence the particle morphology and the mechanisms of the nonspherical‐shape evolution.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
27.
Emergent behavior in active colloids Zöttl, Andreas; Stark, Holger
Journal of physics. Condensed matter,
06/2016, Volume:
28, Issue:
25
Journal Article
Peer reviewed
Open access
Active colloids are microscopic particles, which self-propel through viscous fluids by converting energy extracted from their environment into directed motion. We first explain how artificial ...microswimmers move forward by generating near-surface flow fields via self-phoresis or the self-induced Marangoni effect. We then discuss generic features of the dynamics of single active colloids in bulk and in confinement, as well as in the presence of gravity, field gradients, and fluid flow. In the third section, we review the emergent collective behavior of active colloidal suspensions, focusing on their structural and dynamic properties. After summarizing experimental observations, we give an overview of the progress in modeling collectively moving active colloids. While active Brownian particles are heavily used to study collective dynamics on large scales, more advanced methods are necessary to explore the importance of hydrodynamic and phoretic particle interactions. Finally, the relevant physical approaches to quantify the emergent collective behavior are presented.
The transport of ferrihydrite colloid (FHC) through porous media is influenced by anions (e.g., PO4 3–) and cations (e.g., Ca2+) in the aqueous environment. This study investigated the cotransport of ...FHC with P and P/Ca in saturated sand columns. The results showed that P adsorption enhanced FHC transport, whereas Ca loaded onto P–FHC retarded FHC transport. Phosphate adsorption provided a negative potential on the FHC, while Ca added to P-FHC led to electrostatic screening, compression of the electric double layer, and formation of Ca5(PO4)3OH followed by heteroaggregation at pH ≥ 6.0. The monodentate and bidentate P surface complexes coexisted, and Ca mainly formed a ternary complex with bidentate P ((FeO)2PO2Ca). The unprotonation bidentate P at the Stern 1-plane had a considerable negative potential at the Van der Waals molecular surface. Extending the potential effect to the outer layer of FHC, the potential at the Stern 2-plane and zeta potential exhibited a corresponding change, resulting in a change in FHC mobility, which was validated by comparison of experimental results, DFT calculations, and CD-MUSIC models. Our results highlighted the influence of P and Ca on FHC transport and elucidated their interaction mechanisms based on quantum chemistry and colloidal chemical interface reactions.
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A new generation of photothermal therapeutic agents based on biopolymer dopamine‐melanin colloidal nanospheres is described. Benefitting from their naturally wide distribution in humans, ...dopamine‐melanin colloidal nanospheres exhibit robust biocompatibility and biodegradability, and provide up to 40% photothermal conversion efficiency. After administration, they can efficiently damage tumors at low power density and short irradiation time without damaging healthy tissues.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Nature evolved a variety of hierarchical structures that produce sophisticated functions. Inspired by these natural materials, colloidal self-assembly provides a convenient way to produce structures ...from simple building blocks with a variety of complex functions beyond those found in nature. In particular, colloid-based porous materials (CBPM) can be made from a wide variety of materials. The internal structure of CBPM also has several key attributes, namely porosity on a sub-micrometer length scale, interconnectivity of these pores, and a controllable degree of order. The combination of structure and composition allow CBPM to attain properties important for modern applications such as photonic inks, colorimetric sensors, self-cleaning surfaces, water purification systems, or batteries. This review summarizes recent developments in the field of CBPM, including principles for their design, fabrication, and applications, with a particular focus on structural features and materials' properties that enable these applications. We begin with a short introduction to the wide variety of patterns that can be generated by colloidal self-assembly and templating processes. We then discuss different applications of such structures, focusing on optics, wetting, sensing, catalysis, and electrodes. Different fields of applications require different properties, yet the modularity of the assembly process of CBPM provides a high degree of tunability and tailorability in composition and structure. We examine the significance of properties such as structure, composition, and degree of order on the materials' functions and use, as well as trends in and future directions for the development of CBPM.
Colloids assemble into a variety of bioinspired structures for applications including optics, wetting, sensing, catalysis, and electrodes.
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