Synergistic Mechanoluminescence and Mechanochromism Via Triboelectrification‐Induced Eu³⁺/Eu²⁺ Redox Shuttle

Abstract

Materials capable of simultaneously achieving both mechanoluminescence (ML) and luminescent mechanochromism (L‐MC) hold great promise in smart stimuli‐responsive applications. However, single‐phase and single‐doped inorganic ML materials with pronounced L‐MC behavior are exceptionally rare because of their single luminescent center. This study investigates a unique L‐MC phenomenon in a series of novel triboelectrification‐induced ML materials, Sr5(PO4)3X:Eu3+ (X = F, Cl, Br). These materials exhibit the in situ ionic valence state transition and excitation behaviors of the Eu3+‐Eu2+ ion pair by utilizing the inherent properties of triboelectrification and cause significant differences in the emission spectra during the photoluminescence and ML process. The redox reactions of Eu ions in the ML process are influenced by the synergistic action of the Eu3+‐Eu2+ redox shuttle (suitable redox potential), triboelectrification (driving force), and Sr ion vacancies (catalysts). Hence, this study presents direct experimental evidence for the underlying mechanism of ML and advances the development and applications of triboelectrification‐induced ML materials.