Self‐Assembly of Colloidal Spheres toward Fabrication of Hierarchical and Periodic Nanostructures for Technological Applications

Abstract

to potentially fabricate numerous hierarchical and periodic micro/nanostructure arrays in a large scale. [1][2][3][4][5] Importantly, these ordered micro/nanostructure arrays are essential active components for many technological applications, ranging from data storage, [6] solar cells, [7][8][9] plasmonics to functional coatings, and many others. [10][11][12][13][14][15] Combined with the recent advance in colloidal science, the colloidal spheres with uniform morphology and excellent disperse stability can be further realized by a number of methods, which include the suspension, [16,17] dispersion polymerization, [18,19] emulsion, [20,21] and Stöber techniques. [22] The diameter of colloidal spheres can also be precisely controlled in a wide range, spanning from several micrometers all the way to down to tens of nanometers. Uniquely, these colloidal spheres can be self-assembled into 2D monolayers and 3D periodic multilayers, where they are subsequently utilized as the versatile masks (e.g., optical lens) to achieve fabrication templates by simple surface patterning onto underlying substrates, facilitating the construction of micro/nanostructure arrays with excellent tunability. [23][24][25] Since then, these 2D monolayer colloidal crystals (MCCs) and 3D multilayers have attracted extensive attention for many of their further utilizations. For instance, by using the oxygen plasma and reactive ion etching (RIE) methods, the periodicity, the size, and the shape of individual spheres of MCCs are accurately controlled. [26,27] With further modification, etching, and decoration, the MCCs can be exploited as either the masks for metal catalyst deposition to generate hierarchical and periodic nanostructures on underlying substrates, or the templates for the growth of patterned nanostructures. [28,29] Furthermore, these MCCs can also be utilized as optical lens to construct the periodic nanostructures with photosensitive materials, broadening the preparing routes of hierarchical and periodic nanostructures. [30] In order to prepare the periodic nanostructures, the fabrication process, including the self-assembly of MCCs, the morphological modification of MCCs, and the functionalized decoration, is commonly referred as the nanosphere lithography (NSL). [31][32][33] As compared with conventional lithographic techniques, such as photolithography, [34,35] electron beam lithography, [36] and focused ion beam lithography, [37] NSL can distinctively reduce the manufacturing cost and complexity, The current research status on the self-assembly of colloidal spheres for the fabrication of various hierarchical and periodic nanostructures is summarized, in which these structures exhibit unique properties for different technological applications in plasmonics, surface-enhanced Raman scattering, solar cells, and others. The fundamentals of colloidal self-assembly are first introduced. After which, the functions of the obtained monolayer of colloidal spheres (e.g., nanosphere monolayer) to act as the patterned mask for the subsequent ...

Self‐Assembly of Colloidal Particles for Fabrication of Structural Color Materials toward Advanced Intelligent Systems

“…The colloids would spread as far as possible once a colloidal suspension is dispersed onto a surface and then form a monolayer. Afterward, the film is compressed by a barrier, reducing the available surface area and resulting in an increased surface tension . In the transfer process, a substrate is “scooped” through this compressed film, whereas the lower surface tension provided by the substrate would subsequently cause the colloids to transfer onto it from the interface.…”

Recent progress in periodic patterning fabricated by self-assembly of colloidal spheres for optical applications

“…The feature shape can be diversified by varying the crystal structure of the colloidal mask, etching the mask, altering the incidence angle of the vapor beam, and stepwise manipulating of the mask registry. These nanostructure arrays have broad application prospects, such as photonic crystals, catalysis, templates for fabricating various structures [16][17][18][19][20]. With the development of colloid science, monodisperse colloidal spheres, such as polystyrene or silica, with narrow particle size distribution and good phase stability were synthesized by emulsion, suspension, and various methods [21].…”

Solution‐Processable, High‐Performance Flexible Electroluminescent Devices Based on High‐k Nanodielectrics

“…In addition to high‐ k dielectric layers, light management with optimum electrodes is crucial for high‐performance optoelectronic devices. The structure‐engineered Si‐based electrodes have been used to enhance the performance of optoelectronic devices . However, they had limitations in terms of inherent brittleness and complicated fabrication process.…”