Self-assembly Of Anisotropic Nanoparticles Research Articles

Self-assembly of anisotropic nanoparticles into functional superstructures.

Self-assembly of colloidal nanoparticles (NPs) into superstructures offers a flexible and promising pathway to manipulate the nanometer-sized particles and thus make full use of their unique properties. This bottom-up strategy builds a bridge between the NP regime and a new class of transformative materials across multiple length scales for technological applications. In this field, anisotropic NPs with size- and shape-dependent physical properties as self-assembly building blocks have long fascinated scientists. Self-assembly of anisotropic NPs not only opens up exciting opportunities to engineer a variety of intriguing and complex superlattice architectures, but also provides access to discover emergent collective properties that stem from their ordered arrangement. Thus, this has stimulated enormous research interests in both fundamental science and technological applications. This present review comprehensively summarizes the latest advances in this area, and highlights their rich packing behaviors from the viewpoint of NP shape. We provide the basics of the experimental techniques to produce NP superstructures and structural characterization tools, and detail the delicate assembled structures. Then the current understanding of the assembly dynamics is discussed with the assistance of in situ studies, followed by emergent collective properties from these NP assemblies. Finally, we end this article with the remaining challenges and outlook, hoping to encourage further research in this field.

Size-Separation and Self-Assembly of Anisotropic Nanoparticles in a Coffee-Stain Ring

Nanoparticles deposition via droplet drying technique generally leads to a coffee-stain-like ring. In the case of different shapes and sizes of nanoparticles, such ring-like deposits also demonstrate various phases within the self-assembly superstructures. For broad spectrum sizes in suspension, size-separation effect has not been considered before. Herein, polydisperse gold anisotropic nanoparticles have been prepared via wet chemical synthesis technique. High-resolution scanning electron microscopy (HRSEM) at various positions of a coffee-stain ring displayed both size-separation and self-assembly of nanoparticles. Especially at the outer edges of a ring-like deposit, side-by-side organized arrays of anisotropic nanoparticles have been observed. Likewise, such ordered arrays generally begin with thin nanorods and the width of nanoparticles increases as one moves inward within such arrays. Also, assembly of deposited arrays is more orderly arranged at the periphery of the ring, whereas such order significantly decreases at the interior region of the ring. Furthermore, it has been observed for a mixture of thick–thin nanorods and spheres that only thick nanorods self-assemble into ordered arrays whereas thin rod-sphere was found disordered everywhere within the ring. Nanoscale interactions are quantified for these systems to understand self-assembly behavior of such anisotropic nanoparticles.

Shearing Janus Nanoparticles Confined in Two-Dimensional Space: Reshaped Cluster Configurations and Defined Assembling Kinetics.

The self-assembly of anisotropic nanoparticles (ANPs) possesses a wide array of potential applications in various fields, ranging from nanotechnology to material science. Despite intense research of the thermodynamic self-assembly of ANPs, elucidating their nonequilibrium behaviors under confinement still remains an urgent issue. Here, by performing simulation and theoretical justification, we present for the first time a study of the shear-induced behaviors of Janus spheres (the most elementary ANPs) confined in two-dimensional space. Our results demonstrate that the collective effects of shear and bonding structures can give rise to reshaped cluster configurations, featured by the chiral transition of clusters. Scaling analysis and numerical modeling are performed to quantitatively capture the assembling kinetics of dispersed Janus spheres, thereby suggesting an exotic way to bridge the gap between anisotropic and isotropic particles. The findings highlight confinement and shearing engineering as a versatile strategy to tailor the superstructures formed by ANPs toward unique properties.