Holographic polymer nanocomposites with both high diffraction efficiency and bright upconversion emission by incorporating liquid crystals and core-shell structured upconversion nanoparticles

Abstract

Holographic polymer nanocomposites with upconversion photoluminescence functions have drawn extensive attention. Yet, it still remains challenging to boost the upconversion emission intensity while maintaining a high diffraction efficiency. Herein, we demonstrate a viable approach to fabricating holographic polymer nanocomposites with both high diffraction efficiency and bright upconversion emission by enriching the core-shell structured upconversion nanoparticles (UCNPs) into the constructive regions while enriching the liquid crystal into the destructive regions during photopolymerization. It is found that the mass ratio of oleic acid to H2O (e.g., 2.41–7.65) on the surface of UCNPs plays a critical role to achieve the attractive holographic polymer nanocomposites. Colored holographic images identifiable to the public under room light with four encrypted upconversion emission states (e.g., none, blue, yellow-green and red) are achieved. Moreover, the holographic images are able to show distinct colors at different viewing angles and can be switched by electric fields, showing unclonable features for advanced anti-counterfeiting applications.