Mechanoluminescence from CaCl2:Eu2+

Mechanoluminescent materials have recently attracted considerable attention as they can convert stimulation of mechanical force into photons that can be used in many areas, ranging from basic energy-saving lighting and display to advanced ultrasound-induced biomedical imaging. However, functional and optical materials that feature emission of mechanoluminescence (ML) have only a limited diversity. Here Eu 2+ -doped CaCl 2 was introduced to expand the family of mechanoluminescent materials. It was demonstrated that CaCl 2 :Eu 2+ could emit photoluminescence , radioluminescence , ML, and persistent luminescence (PersL). Eu 2+ ions always acted as luminescent centers (5d→4f transition) during these four emission modes. Moreover, the property of traps of CaCl 2 :Eu 2+ was investigated in detail. Experimental results indicated that there was a competitive relation between ML and PersL, and ML belonged to trap-controlled ML.