Near-Infrared Mechanoluminescence Material from Organic Acid-Aided Process

Near-infrared-mechanoluminescence (NIR-ML) intensity of monoclinic SrAl 2 O 4 doped with Eu 2+ ion (SrAl 2 O 4 :Eu) ML material was tuned by the addition of other metal ions (Cr 3+ , Nd 3+ or both metal ions) into the SrAl 2 O 4 matrix through an organic acid-aided process. This paper especially focused on the synthesis of ML materials with multi-metal elements utilizing an organic acid-aided method and the optical properties of the ML materials such as SrAl 2 O 4 doped with Eu 2+ , Eu 2+ + Cr 3+ , Eu 2+ + Nd 3+ , or Eu 2+ + Cr 3+ + Nd 3+ ions aiming at the expression of multi-wavelength luminescence including visible (0.4–0.7 μ m) and NIR (0.7–2.5 μ m) wavelength ranges. From characterizations of the synthesized materials, we found that the organic acid-aided method could synthesize even the ML material with complicated multi-metal element composition. Moreover, the SrAl 2 O 4 doped with Eu 2+ , Cr 3+ , and Nd 3+ ions gave the highest ML intensity in the wavelength range of 750–1000 nm compared to the other synthesized ML materials, although there was almost no difference in the crystal structure and particle morphology. Correlations between photoluminescence intensity and the additive metal elements into the SrAl 2 O 4 :Eu were suggestive that the NIR-ML intensity was produced by the energy transfer from Eu 2+ ion to Cr 3+ and Nd 3+ ions based on an energy transfer mechanism.