Self-assembly Of Inorganic Nanoparticles Research Articles

Hierarchically Responsive Alternating Nano-Copolymers with Tailored Interparticle Bonds.

Self-assembly of inorganic nanoparticles (NPs) is an essential tool for constructing structured materials with a wide range of applications. However, achieving ordered assembly structures with externally programmable properties in binary NP systems remains challenging. In this work, we assemble binary inorganic NPs into hierarchically pH-responsive alternating copolymer-like nanostructures in an aqueous medium by engineering the interparticle electrostatic interactions. The polymer-grafted NPs bearing opposite charges are viewed as nanoscale monomers ("nanomers"), and copolymerized into alternating nano-copolymers (ANCPs) driven by the formation of interparticle "bonds" between nanomers. The resulting ANCPs exhibit reversibly responsive "bond" length (i.e., the distance between nanomers) in response to the variation of pH in a range of ~7-10, allowing precise control over the surface plasmon resonance of ANCPs. Moreover, specific interparticle "bonds" can break up at pH≥11, leading to the dis-assembly of ANCPs into molecule-like dimers and trimers. These dimeric and trimeric structures can reassemble to form ANCPs owing to the resuming of interparticle "bonds", when the pH value of the solution changes from 11 to 7. The hierarchically responsive nanostructures may find applications in such as biosensing, optical waveguide, and electronic devices.

Self-assembly in biobased nanocomposites for multifunctionality and improved performance.

Concerns of petroleum dependence and environmental pollution prompt an urgent need for new sustainable approaches in developing polymeric products. Biobased polymers provide a potential solution, and biobased nanocomposites further enhance the performance and functionality of biobased polymers. Here we summarize the unique challenges and review recent progress in this field with an emphasis on self-assembly of inorganic nanoparticles. The conventional wisdom is to fully disperse nanoparticles in the polymer matrix to optimize the performance. However, self-assembly of the nanoparticles into clusters, networks, and layered structures provides an opportunity to address performance challenges and create new functionality in biobased polymers. We introduce basic assembly principles through both blending and in situ synthesis, and identify key technologies that benefit from the nanoparticle assembly in the polymer matrix. The fundamental forces and biobased polymer conformations are discussed in detail to correlate the nanoscale interactions and morphology with the macroscale properties. Different types of nanoparticles, their assembly structures and corresponding applications are surveyed. Through this review we hope to inspire the community to consider utilizing self-assembly to elevate functionality and performance of biobased materials. Development in this area sets the foundation for a new era of designing sustainable polymers in many applications including packaging, construction chemicals, adhesives, foams, coatings, personal care products, and advanced manufacturing.

Building ordered nanoparticle assemblies inspired by atomic epitaxy.

Self-assembly of inorganic nanoparticles into mesoscopic or macroscopic nanoparticle assemblies is an efficient strategy to fabricate advanced devices with emergent nanoscale functionalities. Furthermore, assembly of nanoparticles onto substrates may enable the fabrication of substrate-integrated devices, akin to atomic crystal growth on a substrate. Recent progress in nanoparticle assembly suggests that ordered nanoparticle assemblies could be well produced on a selected substrate, referred to as soft epitaxial growth. Herein, recent advances in soft epitaxial growth of a nanoparticle assembly are presented, including the assembly strategies, the choice of substrate and the epitaxial modes. Perspectives are also discussed for the material design based on substrate-integrated soft epitaxial growth.

Engineered Anisotropic Fluids of Rare-Earth Nanomaterials.

The self-assembly of inorganic nanoparticles into well-ordered structures in the absence of solvents is generally hindered by van der Waals forces, leading to random aggregates between them. To address the problem, we functionalized rigid rare-earth (RE) nanoparticles with a layer of flexible polymers by electrostatic complexation. Consequently, an ordered and solvent-free liquid crystal (LC) state of RE nanoparticles was realized. The RE nanomaterials including nanospheres, nanorods, nanodiscs, microprisms, and nanowires all show a typical nematic LC phase with one-dimensional orientational order, while their microstructures strongly depend on the particles' shape and size. Interestingly, the solvent-free thermotropic LCs possess an extremely wide temperature range from -40 °C to 200 °C. The intrinsic ordering and fluidity endow anisotropic luminescence properties in the system of shearing-aligned RE LCs, offering potential applications in anisotropic optical micro-devices.

Bioinspired synthesis of silica nanocups - Polymer-mediated self-assembly of inorganic nanoparticles

Nature oversees a vast array of amazing shapes formed by organisms such as plants, fungi and animals. Some of these manifest as intricate patterns in structures like coral and the nests of insects and birds. Associate Professor Ayae Sugawara-Narutaki, from the Department of Materials Chemistry at Nagoya University, Japan has a particular interest in these patterns. Sugawara-Narutaki's team focuses on research inspired by these self-organised nanostructures to develop nanomaterials for a variety of health-related applications. The ability of these nanomaterials to self-assemble and self-organise in a liquid phase has attracted a great deal of interest from materials scientists the world over.

Staged Surface Patterning and Self-Assembly of Nanoparticles Functionalized with End-Grafted Block Copolymer Ligands.

Using two orthogonal external stimuli, programmable staged surface patterning and self-assembly of inorganic nanoparticles (NPs) was achieved. For gold NPs capped with end-grafted poly(styrene-block-(4-vinylbenzoic acid)), P(St-block-4VBA), block copolymer ligands, surface-pinned micelles (patches) formed from NP-adjacent PSt blocks under reduced solvency conditions (Stimulus 1); solvated NP-remote P(4VBA) blocks stabilized the NPs against aggregation. Subsequent self-assembly of patchy NPs was triggered by crosslinking the P(4VBA) blocks with copper(II) ions (Stimulus 2). Block copolymer ligand design has a strong effect on NP self-assembly. Small, well-defined clusters assembled from NPs functionalized with ligands with a short P(4VBA) block, while NPs tethered with ligands with a long P(4VBA) block formed large irregularly shaped assemblies. This approach is promising for high-yield fabrication of colloidal molecules and their assemblies with structural and functional complexity.

Self-Assembly of Chiral Gold Clusters into Crystalline Nanocubes of Exceptional Optical Activity.

Self-assembly of inorganic nanoparticles into ordered structures is of interest in both science and technology because it is expected to generate new properties through collective behavior; however, such nanoparticle assemblies with characteristics distinct from those of individual building blocks are rare. Herein we use atomically precise Au clusters to make ordered assemblies with emerging optical activity. Chiral Au clusters with strong circular dichroism (CD) but free of circularly polarized luminescence (CPL) are synthesized and organized into uniform body-centered cubic (BCC) packing nanocubes. Once the ordered structure is formed, the CD intensity is significantly enhanced and a remarkable CPL response appears. Both experiment and theory calculation disclose that the CPL originates from restricted intramolecular rotation and the ordered stacking of the chiral stabilizers, which are fastened in the crystalline lattices.

Tunable porous nanoallotropes prepared by post-assembly etching of binary nanoparticle superlattices.

Self-assembly of inorganic nanoparticles has been used to prepare hundreds of different colloidal crystals, but almost invariably with the restriction that the particles must be densely packed. Here, we show that non-close-packed nanoparticle arrays can be fabricated through the selective removal of one of two components comprising binary nanoparticle superlattices. First, a variety of binary nanoparticle superlattices were prepared at the liquid-air interface, including several arrangements that were previously unknown. Molecular dynamics simulations revealed the particular role of the liquid in templating the formation of superlattices not achievable through self-assembly in bulk solution. Second, upon stabilization, all of these binary superlattices could be transformed into distinct "nanoallotropes"-nanoporous materials having the same chemical composition but differing in their nanoscale architectures.

Self-assembly of inorganic nanoparticles: Ab ovo(a)(a)Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

There are numerous remarkable studies related to the self-organization of polymers, coordination compounds, microscale particles, biomolecules, macroscale particles, surfactants, and reactive molecules on surfaces. The focus of this paper is on the self-organization of nanoscale inorganic particles or simply nanoparticles (NPs). Although there are fascinating and profound discoveries made with other self-assembling structures, the ones involving NPs deserve particular attention because they (a) are omnipresent in Nature; (b) have relevance to numerous disciplines (physics, chemistry, biology, astronomy, Earth sciences, and others); (c) embrace most of the features, geometries, and intricacies observed for the self-organization of other chemical species; (d) offer new tools for studies of self-organization phenomena; and (e) have a large economic impact, extending from energy and construction industries, to optoelectronics, biomedical technologies, and food safety. Despite the overall success of the field it is necessary to step back from its multiple ongoing research venues and consider two questions: What is self-assembly of nanoparticles? and Why do we need to study it? The reason to bring them up is to achieve greater scientific depth in the understanding of these omnipresent phenomena and, perhaps, deepen their multifaceted impact.

Magnetic field-induced self-assembly of iron oxide nanocubes.

Self-assembly of inorganic nanoparticles has been studied extensively for particles having different sizes and compositions. However, relatively little attention has been devoted to how the shape and surface chemistry of magnetic nanoparticles affects their self-assembly properties. Here, we undertook a combined experiment-theory study aimed at better understanding of the self-assembly of cubic magnetite (Fe3O4) particles. We demonstrated that, depending on the experimental parameters, such as the direction of the magnetic field and nanoparticle density, a variety of superstructures can be obtained, including one-dimensional filaments and helices, as well as C-shaped assemblies described here for the first time. Furthermore, we functionalized the surfaces of the magnetic nanocubes with light-sensitive ligands. Using these modified nanoparticles, we were able to achieve orthogonal control of self-assembly using a magnetic field and light.

Design and Application of Inorganic Nanoparticle Superstructures: Current Status and Future challenges

Self-assembly of inorganic nanoparticles (NPs) into superstructures, which is used as a general way to integrate functional inorganic NPs into macroscale devices, has attracted much research interest. This review will summarize the recent progress and discuss future challenges of the inorganic NP superstructures. Examples include both DNA-based and polymer-based NP assemblies with controlled positioning and geometries, and quasicrystalline ordered structures from the self-assembly of binary or ternary NPs. Different from their individual NP counterparts, these self-assembled superstructures possess unique properties, such as optical chirality and dynamic structural change under an external stimulus. Due to their diversified structures and functionalities, inorganic NP superstructures have shown a wide range of promise for applications in electronic and photonic devices, such as field-effect transistors, magnetoresistive components, optical information recording, and solar cells.

Chemically induced self-assembly of spherical and anisotropic inorganic nanocrystals

The self-assembly of inorganic nanoparticles is a research area of great interest aiming at the fabrication of unique mesostructured materials with intrinsic properties. Although many assembly strategies have been reported over the years, chemically induced self-assembly remains one of the dominant approaches to achieve a high level of nanoparticle organization. In this feature article we will review the latest developments in assembly driven by the active manipulation of nanoparticle surfaces.

Self-Assembly of Gold Nanoparticles as Colloidal Crystals Induced by Polymerization of Amphiphilic Monomers

The self-assembly of inorganic nanoparticles (NPs) into hierarchical structures on different length scales is one of the main aspects of “bottom-up” approaches to create materials with specific electronic, optical, or magnetic properties. We report a new procedure to generate and stabilize colloidal crystals formed by gold NPs during a polymerization reaction, leading to an amphiphilic physical gel. Dodecanethiol-stabilized gold NPs with an average diameter of 2 nm were synthesized and dissolved (0.15 wt %) in a stoichiometric mixture of diglycidylether of bisphenol A (DGEBA) and dodecylamine (DA). The polymerization of DGEBA with DA was carried out at 100 °C leading to a linear polymer that very slowly generated an amphiphilic physical gel by the self-assembly of dodecyl chains. The formation of the physical gel was followed by rheometry and its structure investigated by SAXS. In the course of this polymerization, gold NPs were phase-separated generating colloidal crystals with dimensions varying from tens to hundreds of nanometers (TEM) and exhibiting a 3D hexagonal close-packed (HCP) structure (SAXS). The size of the gold NPs forming the colloidal crystals was about twice the original size, meaning that a coalescence process took place. This was confirmed by the increase in the intensity of the plasmon band in UV−visible absorption spectra. Partitioning and irreversible adsorption of large colloidal particles at the air−polymer interface were observed, leading to highly ramified fractal structures. This was explained by the high energy needed to remove large colloidal particles attached at the interface. The polymer precursors used in the present study may, in principle, be employed for different kinds of NPs stabilized by hydrophobic chains to generate dispersions of colloidal crystals in polymer gels or percolating fractal structures at the air−polymer interface.