Synthesis and Spatial Order Characterization of Controlled Silica Particle Sizes Organized as Photonic Crystals Arrays

Abstract

The natural occurrence of precious opals, consisting of highly organized silica particles, has prompted interest in the synthesis and formation of these structures. Previous research has shown that a highly organized photonic crystal (PhC) array is only possible when it is based on a low polydispersity index (PDI) sample of particles. In this study, a solvent-only variation method is used to synthesize different sizes of silica particles (SiPs) by following the traditional sol-gel Stöber approach. The controlled rate of the addition of the reagents promoted the homogeneity of the nucleation and growth of the spherical silica particles, which in turn yielded a low PDI. The opalescent PhC were obtained via self-assembly of these particles using a solvent evaporation method. Analysis of the spatial statistics, using Voronoi tessellations, pair correlation functions, and bond order analysis showed that the successfully formed arrays showed a high degree of quasi-hexagonal (hexatic) organization, with both global and local order. Highly organized PhC show potential for developing future materials with tunable structural reflective properties, such as solar cells, sensing materials, and coatings, among others.

Relationship between deposition techniques and nanoparticle dispersions for flexible and printed electronics

“…where V m and A m is the volume and area occupied by each micelle, respectively. Assuming perfect sphere packing, the energetically most favourable, densest packing in two dimensions is a triangular arrangement, more commonly known as hexagonal close packing [69][70][71][72]. As diblock copolymer micelles and colloids typically form quasi-hexagonal arrangements [40,69,[71][72][73][74][75], we, therefore, assume a perfect hexagonal arrangement and that each micelle will occupy an area represented by a hexagon; the hexagonal covering area can be related to the interparticle distance by,…”

“…Angular order is related to the relative arc-separation of the 'bonds' or touching contacts between a particle and its neighbors. Complete periodicity is seen when the neighbors for any particular particle have the same angular arc symmetry, as well as being equidistant, with maximized covering area due to the equivalent position of each particle relative to all others [69,70]. If any one of these types of order are not met, the system can be considered in a mesophase [131], such as that observed for plastic crystals (limited orientational or rotational order, but long-range translational order [132]) or liquid crystals (limited translational order but longrange angular order) [133].…”

“…A lower disorder parameter indicates a more ordered system. Greater details on these ordering parameters can be found in Bumstead et al [69] and Alvarez et al [70].…”

Peculiarities of Eu3+ Photoluminescence in Opal Photonic Crystal Films and Heterostructures Based of Them

“…Artificial opals are porous matrices composed of sequential layers of close-packed particles with diameters of hundreds of nanometers. Generally, silica (SiO 2 ) particles are used [18], but other ones made of polystyrene (PS) or polymethyl methacrylate (PMMA) can also be exploited [19]. To vary the dielectric contrast and to enlarge the functionality of opal PhCs, the matrices are impregnated with magnetic clusters [20,21], active dielectrics [22][23][24], semiconductors [25][26][27],organic and laser-active materials [28][29][30].…”

Special Issue: Soft Photonic Crystals and Metamaterials

“…There are two papers related to smart windows (Tseng et al [1] as well as Yokota et al [2]). Two papers involve microparticle arrangement in colloidal and photonic crystalline structures (Seki et al [3] and Alvarez et al [4]). There are three related to switchable or tunable liquid crystal devices (Nys et al [5], Yu et al [6], and Bikbaev et al [7]).…”