Reversible Luminescence Change of Upconversion Nanocrystals Nanoemulsion Embedded Hydrogel Microstructures

Abstract

We developed a facile synthesis method of upconversion nanocrystals (UCNs) embedded photo-curable nanoemulsion resin and fabricated dynamic hydrogel microstructures representing reversible luminescence intensity change. UCNs are drawn attention in bio-imaging, sensors and anti-counterfeiting systems due to its unique optical properties such as large anti-Stokes shift, physicochemical stability and low auto-fluorescence. We homogeneously incorporated UCNs into photo-curable nanoemulsion hydrophilic resin and fabricated upconverting luminescence hydrogel microstructures with a huge reversible volume change during contraction and expansion. This maximized reversible volumetric change of hydrogel microstructures induced 6-fold luminescence enhancement upon contraction. We demonstrate a responsive hidden letter encryption technology using UCNs embedded photo-curable nanoemulsion system.