Photoluminescence modification in upconversion rare-earth fluoridenanocrystal array constructed photonic crystals

Abstract

In this work, we fabricated the upconversion inverse opals with hierarchical rare-earth fluoride arrays by inducing NaYF₄:Yb³⁺/Er³⁺ nanocrystal self-assembly inside the voids of a self-organized PS template via the MIMIC method. We induced cubic phase α-NaYF₄:Yb³⁺/Er³⁺ nanocrystals to assemble in polystyrene (PS) colloidal crystals. After removing the PS colloidal template, highly ordered 3D inverse opal photonic crystals (PCs) hierarchical arrays consisting of densely packed cubic or hexagonal NaYF₄:Yb³⁺/Er³⁺ nanocrystals were obtained. The photonic band structure of the materials can be controlled in a way that modifies the upconversion (UC) photoluminescence by adjusting the macroporous diameter of the NaYF₄ photonic crystals. It is found that the photonic stop band can modify the emission band in the spectral region where the overlap occurs, producing a depression in the emission band corresponding to the stop band position, while the photoluminescence lifetime of the Er³⁺ ions in the inverse opals is also increased.