Inorganic photochromism material SrHfO3:Er3+ integrating multiple optical behaviors for multimodal anti-counterfeiting

Abstract

Photochromic materials usually have different physical and chemical properties when they are in different states. Inorganic photochromic materials are widely used in the fields of information storage, optical switches and sensors due to their long lifetime, good thermal stability and fatigue resistance. However, the current inorganic photochromic materials, possessing a unitary optical property, cannot fulfill the requirement of multimodal high-level security anti-counterfeiting. In this work, we report the multiple optical behaviors integrated inorganic photochromic Er3+-doped strontium hafnate ceramics. It integrates multiple optical functions, including photochromism, downshifting photoluminescence, up-conversion luminescence, afterglow, and thermoluminescence. The fluorescence modulation contrast (FMC) maximum of SrHfO3: Er3+ can achieve as high as to 77.21% in the mode of photochromism-driven the quenching of downshifting photoluminescence. The FMC maximum can approach 70.24% in the mode of photochromism-driven the quenching of up-conversion luminescence. By alternating the light stimulation and thermal field effect, both photochromism and fluorescence modulation exhibit excellent stability and robust fatigue resistance. The mechanisms of the observed photochromism, downshifting and up-conversion luminescence, fluorescence modulation, afterglow, and thermoluminescence were studied systematically. The combination of the multiple optical behaviors functionalizes the as-obtained material for versatile applications. As a proof of concept, a flexible film was designed and prepared, demonstrating the practical application of SrHfO3: Er3+ material for multimodal high-level security anti-counterfeiting.