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Abstract

We report an in-situ observation of wet opal formation from a dilute colloidal suspension by using time-resolved transmission spectroscopy. The formation involves rather complex partial processes that include particle migration, particle ordering (crystallization) into differently oriented domains, and continuous compaction. The initial particle ordering results in an fcc lattice with an interparticle distance larger than particle diameter. The crystallization is followed by a slow but continuous compaction until the wet opal fills the capillary cell completely. The time behavior of the background of the extinction spectra indicates that there is no disordered dense state preceding the opal growth front. Instead, it seems that the continuous compaction process heals pointlike defects but at the same time induces domain-related defects. Similar formation processes likely occur for other deposition methods like vertical and horizontal deposition methods as well.