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