Designing photonic crystals with ultranarrow stopband through spontaneouscrystallization of polymeric colloids swollen by resin
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초록
내용
Self-assembly of colloidal nanoparticles has been used as a facile and cheap method to make wide-sized photonic crystals, but the reflectance spectrum is usually wide and low due to a low refractive index contrast and difficulties in controlling the crystal orientations. In this study, the crosslinked monodisperse polystyrene nanoparticles are dispersed in the trimethylolpropane ethoxylate triacrylate(ETPTA) resin. Polystyrene nanoparticles swollen by ETPTA spontaneously crystallize in between two glasses. The crystals show very narrow and high reflectance peaks simultaneously which were rarely obtained in previous studies. The crystallization occurs only when the volume fractions exceeds certain values. The rate of crystallization increases as volume fraction of particles and temperature increase, resulting in a lower and wide peak. UV curing of the resin reduce the refractive indices contrast between particles and medium, further decreasing the width and height of peak.