Cr ³⁺ ‐Activated Tunable Near‐Infrared Mechanoluminescence Materials for Potential Water Pollutant Monitoring

Abstract Mechanoluminescence (ML) materials can directly convert mechanical energy into light energy, demonstrating significant application potential in various fields. However, the limited spectral range of ML materials has hindered the application in complex environments such as biological stress detection and water quality monitoring. Here, we reported the Cr 3+ ‐activated high‐perfromance NIR ML with continuous spectral tuning from a sharp R line (698 nm) to a broadband range (650–1000 nm) based on local crystal field engineering. Comprehensive characterizations (Raman, TEM, XPS and EPR) revealed the potential origin of ML, addressing synergistic effects of Cr 3+ ‐induced lattice distortion and oxygen vacancy defects. Lattice distortion breaks the central symmetry to induce the piezoelectric effect, driving carrier migration to Cr 3+ ion, in which oxygen vacancy provides a fast channel for carrier migration. Based on continuous NIR‐ML spectral tunability, a novel water quality monitoring technology is demonstrated. The narrow band emission is used to detect sulfonated phthalocyanine cobalt, while broadband emission is used to detect carbon black. This work provides novel insights into the design of spectrally tunable NIR‐ML materials and their application in real‐time monitoring of water quality.