Bright Chromium-Sensitized Lanthanide NIR-II Mechanoluminescence in a Piezoelectric Oxide.

Liu, Shengqiang; Guo, Yang; Song, Zhen; Peng, Dengfeng; Liu, Quanlin; Wang, Feng · Adv Mater · 2025

basic_science · Level V

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Abstract

Near-infrared (NIR) luminescent materials are critical components of high-performance optical devices for frontier applications in anti-counterfeiting, non-destructive analysis, and deep-tissue imaging. In this work, a bright Cr<sup>3+</sup>-sensitized lanthanide NIR-II mechanoluminescence (ML) is developed in piezoelectric β-Ga<sub>2</sub>O<sub>3</sub>. Specifically, a nearly complete energy transfer (ET) from highly doped Cr<sup>3+</sup> ions to Yb<sup>3+</sup> and Er<sup>3+</sup> acceptors is observed, resulting in pronounced ML at 1002 and 1542 nm. The NIR-II luminescence intensity is further improved by cation alloying due to the promotion of octahedral distortion, culminating in 5.9- and 3.0-fold stronger ML emissions compared to the well-established CaZnOS:Yb<sup>3+</sup> and CaZnOS:Er<sup>3+</sup>, respectively. Furthermore, mechanistic investigations revealed that the ML behavior with high dopant concentration is enabled by strain-induced piezoelectric potential without the involvement of trapping states, thus exhibiting exceptional cycling stability. Finally, an innovative multi-level encryption framework is established for information protection with wavelength-selective readout capabilities by optical or mechanical excitation.