Mechano-luminescence Behavior of Lanthanide-Doped Fluoride Nanocrystals for Three-Dimensional Stress Imaging

Abstract

<p>Pervasive mechanical force in nature and human activitiesis closelyrelated to intriguing physics and widespread applications. However,describing stress distribution timely and precisely in three dimensionsto avoid "groping in the dark" is still a formidablechallenge, especially for nonplanar structures. Herein, we realizethree-dimensional (3D) stress imaging for sharp arbitrary targetsvia advanced 3D printing, owing to the use of fluoride nanocrystal-(NC)-basedink. Notably, a fascinating mechano-luminescence (ML) is observedfor the homogeneously dispersed NaLuF4:Tb3+ NCs(similar to 25 nm) with rationally designed deep traps (at 0.88 and 1.02eV) via incorporating Cs+ ions and using X-ray irradiation.Carriers captured in the corresponding traps are steadily releasedunder mechanical stimulations, which enables a ratio metric luminescenceintensity based on the applied force. As a result, a significant mechano-opticalconversion and superior optical waveguide of the corresponding transparentprinted targets demonstrate stress in 3D with a high spatial and temporalresolution based on stereovision. These results highlight the opticalfunction of the 3D-printed fluoride NCs, which cast light into theblack boxes of stress described in space, benefiting us in understandingthe ubiquitous force relevant to most natural and engineering processes.<br></p>