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Magnetic nanoparticles are promising for a variety of applications, such as biomedical devices, spin electronics, magnetic data storage media, to name a few. However, these goals may only be reached if stable and organized structu...
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Magnetic nanoparticles are promising for a variety of applications, such as biomedical devices, spin electronics, magnetic data storage media, to name a few. However, these goals may only be reached if stable and organized structures are fabricated. In this article, we report on a single-step synthetic route with the coprecipitation method, in which iron oxide magnetic nanoparticles (Fe _3O _4 NPs) were stabilized in aqueous media using the poly (diallyldimethylammonium chloride) (PDAC) polyelectrolyte. The Fe _3O _4 NPs had a diameter of ca. 5 nm, according to transmission electron microscopy (TEM) images, being arranged in an inverse spinel structure typical of magnetite. An investigation with infrared spectroscopy indicated that the mechanisms of stabilization in the polymer matrix were based on the interaction between quaternary amide groups from PDAC and the nanoparticle surface. The Fe _3O _4-PDAC NPs exhibited considerable magnetic susceptibility, with a monotonic increase in the magnetization with decreasing temperature. These Fe _3O _4-PDAC NPs were immobilized in layer-by-layer (LbL) films, being alternated with layers of poly (vinylsulfonic acid) (PVS). The LbL films were much rougher than typical films made with polyelectrolytes, and Fe _3O _4-PDAC NPs have been responsible for the high electrocatalytic activity toward H _2O _2 reduction, with an overpotential shift of 0.69 V. Overall, the stability, magnetic properties and film-forming ability indicate that the Fe _3O _4-PDAC NPs may be used for nanoelectronics and bioelectrochemical devices requiring reversible and magnetic redox materials.
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We propose a strategy for robust high-quality self-assembly of nontrivial periodic structures out of patchy particles and investigate it with Brownian dynamics simulations. Its first element is the use of specific patch-patch and ...
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We propose a strategy for robust high-quality self-assembly of nontrivial periodic structures out of patchy particles and investigate it with Brownian dynamics simulations. Its first element is the use of specific patch-patch and shell-shell interactions between the particles, which can be implemented through differential functionalization of patched and shell regions with specific DNA strands. The other key element of our approach is the use of a layer-by-layer protocol that allows one to avoid the formation of undesired random aggregates. As an example, we design and self-assemble in silico a version of a double diamond lattice in which four particle types are arranged into bcc crystal made of four fcc sublattices. The lattice can be further converted to cubic diamond by selective removal of the particles of certain types. Our results demonstrate that by combining the directionality, selectivity of interactions, and the layer-by-layer protocol, a high-quality robust self-assembly can be achieved.
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Graphene/polyaniline (PANI) multilayer films were prepared via alternate deposition of negatively charged graphene oxide (GO) and positively charged PANI upon electrostatic interaction, followed by the reduction of their GO compon...
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Graphene/polyaniline (PANI) multilayer films were prepared via alternate deposition of negatively charged graphene oxide (GO) and positively charged PANI upon electrostatic interaction, followed by the reduction of their GO components with hydroiodic acid. The thickness of the multilayer film increased linearly with the number of its bilayers and that of each bilayer was measured to be about 3 nm. Cyclic voltammetry studies indicated that these thin composite films were electroactive, and their redox reactions were related to the insertion-extraction of counter ions in PANI layers. Furthermore, the composite films were tested to be promising electrode materials for electrochromic devices even without using the conventional indium tin oxide (ITO) electrodes.
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摘要 :
Graphene/polyaniline (PANI) multilayer films were prepared via alternate deposition of negatively charged graphene oxide (GO) and positively charged PANI upon electrostatic interaction, followed by the reduction of their GO compon...
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Graphene/polyaniline (PANI) multilayer films were prepared via alternate deposition of negatively charged graphene oxide (GO) and positively charged PANI upon electrostatic interaction, followed by the reduction of their GO components with hydroiodic acid. The thickness of the multilayer film increased linearly with the number of its bilayers and that of each bilayer was measured to be about 3 nm. Cyclic voltammetry studies indicated that these thin composite films were electroactive, and their redox reactions were related to the insertion-extraction of counter ions in PANI layers. Furthermore, the composite films were tested to be promising electrode materials for electrochromic devices even without using the conventional indium tin oxide (ITO) electrodes.
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Cellulose nanocrystals (CNC) with 3-4 nm in diameter and 100-300 nm long were obtained by sulphuric acid hydrolysis from cellulose pulp. CNC were deposited by layer-by-layer (LBL) assembly with cationic polyelectrolyte, poly(allyl...
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Cellulose nanocrystals (CNC) with 3-4 nm in diameter and 100-300 nm long were obtained by sulphuric acid hydrolysis from cellulose pulp. CNC were deposited by layer-by-layer (LBL) assembly with cationic polyelectrolyte, poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDDA), to prepare thin films. PDDA is a fully charged polyelectrolyte while PAH is partially charged and its charge density is dependent on pH value. We compared the LBL assembly behaviour of CNC with weak and strong polyelectrolyte.
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Poly(ferrocenyl(3-bromopropyl)methylsilane) and poly(ethylene imine) are employed in a layer-by-layer deposition process to form covalently connected, redox-active multilayer thin films by means of an amine alkylation reaction. Th...
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Poly(ferrocenyl(3-bromopropyl)methylsilane) and poly(ethylene imine) are employed in a layer-by-layer deposition process to form covalently connected, redox-active multilayer thin films by means of an amine alkylation reaction. The stepwise buildup of these multilayers on silicon, ITO, and quartz substrates was monitored by UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), static contact angle measurements, surface plasmon resonance (SPR), atomic force microscopy, ellipsometry, and cyclic voltammetry, which provide evidence for a linear increase in multilayer thickness with the number of deposited bilayers. Upon oxidation and reduction, these covalently interconnected layers do not disassemble, in contrast to poly(ferrocenylsilane) (PFS) layers featuring similar backbone structures that are held together by electrostatic forces. The PFS/PEI multilayers are effective for the electrochemical sensing of ascorbic acid and hydrogen peroxide and show improved sensing performance at higher bilayer numbers. These covalently linked layers are readily derivatized further and can therefore be regarded as a versatile platform for creating robust, tailorable, redox-active interfaces with applications in sensing and biofuel cells.
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The environment-material interface plays a key role in determining the performance of a material in a variety of applications such as separating gas molecules or solutes, harnessing photons or electrons, and responding to biomolec...
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The environment-material interface plays a key role in determining the performance of a material in a variety of applications such as separating gas molecules or solutes, harnessing photons or electrons, and responding to biomolecules or organisms. Layer-by-layer assembly (LbL) technologies provide a means of controlling the surface and interface of a material, resulting in a composite in which the interface and the bulk of the material can be designed and controlled to a large extent independently. In addition, some exciting and novel applications have been widely studied for LbL assembly, such as vibration damping composites, shape memory materials, advanced dielectric composites, and radiation protection composites. In this paper, we review the development history and state-of-the-art of LbL assembly, and highlight the limitations of traditional LbL assembly in polymer solutions. As the forced assembly technology is simple, fast, and widely used for polymer substrates, it has attracted extensive attention and shows potential for application. Moreover, with the emergence of a new strategy and mechanism of LbL assembly (e.g., assembly with polymer crystallization) and the expansion of application fields, a comprehensive review focusing on the progress of LbL assembly in recent years is still lacking, which is the motivation for this review. Topics such as morphological characterization and control methods, the resulting multilayered interfaces, and their outstanding properties are discussed. A general but comprehensive review covering all aspects of the LbL assembly from mechanism to application has been carried out. (C) 2018 Elsevier B.V. All rights reserved.
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The layer-by-layer (LBL) assembly technique is currently one of the most widely utilized methods for the preparation of nanostructured, multilayered thin films. The structure of LBL films is typically controlled by varying the dep...
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The layer-by-layer (LBL) assembly technique is currently one of the most widely utilized methods for the preparation of nanostructured, multilayered thin films. The structure of LBL films is typically controlled by varying the deposition sequence of adsorbed layers, leading to stratified assemblies. For specific, non-spherical inorganic LBL components, such as sheets, or axial nanocolloids, such as nanotubes, nanowires, nanowiskers, or nanorods, the structure of the films can also be controlled by their orientation. As such, clay nanosheets spontaneously adsorb almost exclusively in the orientation parallel to the substrate whilst assembly of axial nanocolloids under conditions of shear or dewetting results in partial alignment of the fibrous components. Morphological or structural control of the multilayers can also be imparted by the choice of the assembly method (e.g. spin coating versus dip coating), the assembly conditions, or post-assembly processing of the assembly. The shape andsurface morphology of the assemblies can also be tailored by the structure or shape of the substrate, as has been shown in the preparation of hollow capsules1'1 or sculptured/perforated membranes.
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The fabrication of polyelectrolyte multilayer films (PEMs) using the Layer-by-Layer (LbL) method is one of the most versatile approaches for manufacturing functional surfaces. This is the result of the possibility to control the a...
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The fabrication of polyelectrolyte multilayer films (PEMs) using the Layer-by-Layer (LbL) method is one of the most versatile approaches for manufacturing functional surfaces. This is the result of the possibility to control the assembly process of the LbL films almost at will, by changing the nature of the assembled materials (building blocks), the assembly conditions (pH, ionic strength, temperature, etc.) or even by changing some other operational parameters which may impact in the structure and physico-chemical properties of the obtained multilayered films. Therefore, the understanding of the impact of the above mentioned parameters on the assembly process of LbL materials plays a critical role in the potential use of the LbL method for the fabrication of new functional materials with technological interest. This review tries to provide a broad physicochemical perspective to the study of the fabrication process of PEMs by the LbL method, which allows one to take advantage of the many possibilities offered for this approach on the fabrication of new functional nanomaterials. (C) 2020 Elsevier B.V. All rights reserved.
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Nanotube-nanoparticle composites are fabricated by template-directed automatic layer-by-layer assembly with the assistance of pressure. This assembly strategy above allows the facile construction of uniform complex nanostructures ...
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Nanotube-nanoparticle composites are fabricated by template-directed automatic layer-by-layer assembly with the assistance of pressure. This assembly strategy above allows the facile construction of uniform complex nanostructures with ultra-multilayers (approximate to 200). Importantly, it takes much less time than conventional manual manipulation.
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