Synthesis of Silica Microspheres—Inspired by the Formation of Ice Crystals—With High Homogeneous Particle Sizes and Their Applications in Photonic Crystals

Abstract

Silica microspheres (SMs) must possess the performances of desirable monodispersity, narrow particle size distribution, and high sphericity for preparing photonic crystals (PCs) and other materials such as microspheres reference material, etc. We have adopted the techniques of increasing reactant concentration and raising the temperature to improve the synthesis rate of SMs, gaining inspiration from the formation mechanism of ice crystals. SMs with uniform particle sizes (polydispersity index less than 0.05) and good spherical features were fabricated through homogeneous nucleation. The mathematical relationship between particle sizes of SMs and reactant concentrations is further fitted. High accuracy of the regression equation is verified by an F-test and verification experiment. Highly ordered PCs (the stacking fault is about 1.5%, and the point defect is about 10−3) with dense stacked opal structures have been obtained by self-assembly of SMs. In addition, highly ordered PCs (the stacking fault is about 3%, and the point defect is about 10−3) with non-dense packed opal structure and inverse opal structure were successfully prepared. PCs of inverse opal structure were used to examine their response characteristics to identify ethanol, exhibiting good performance. Our research may provide significant inspiration for the development of other sorts of microspheres.

Three-Dimensional Photonic Crystal Bulks with Outstanding Mechanical Performance Assembled by Thermoforming-Etching Cross-linked Polymer Microspheres

“…The structural color, exhibiting highlights of environment-friendly, , never fading, − and angle dependence, , generated from Bragg diffraction in a photonic crystal (PC) structure is a significant direction of applications including displays, − optical anti-counterfeiting, − optical devices, − chemical and biological sensors, − and so forth. To date, various exiting assembly technologies (such as self-assembly of colloidal particles, − spin coating, − chemical vapor deposition, − holographic lithography, and , co-extrusion − ) have drastically improved the optical properties and microstructure of PCs. , Particularly, PCs with an ordered arrangement of assembled microspheres exhibit high and narrow Bragg peak and obvious angle dependence attributed to high refractive index, uniform microspheres, complete structure, and less microstructure defect. , It is important to note that many novel methods have been reported to enhance the mechanical performance of the PC film with excellent optical properties. For example, Chen et al designed a protective film produced by whey protein, which can be formed on the surface of artificially synthesized PCs and make the PCs friction- and impact-resistant .…”

“…36,37 Particularly, PCs with an ordered arrangement of assembled microspheres exhibit high and narrow Bragg peak and obvious angle dependence attributed to high refractive index, uniform microspheres, complete structure, and less microstructure defect. 38,39 It is important to note that many novel methods have been reported to enhance the mechanical performance of the PC film with excellent optical properties. For example, Chen et al designed a protective film produced by whey protein, which can be formed on the surface of artificially synthesized PCs and make the PCs friction-and impact-resistant.…”