Alkaline-earth-metal-ion blending enhanced mechanoluminescence of lanthanide ions in MZnOS hosts for stress sensing and anticounterfeiting†

Mechanoluminescent (ML) materials with highly-efficient and multicolored emission are strongly anticipated in the field of stress sensing and information encryption. Here, a combined strategy of alkaline-earth-metal-ion blending in hosts and lanthanide-ion doping is developed to design ML materials. The strategy can be conveniently performed via doping binary (Ca, Sr)ZnOS hosts with lanthanide ions at optimized Ca²⁺/Sr²⁺ ratios. Four different lanthanide ions, including Er³⁺, Dy³⁺, Sm³⁺, and Yb³⁺, can be separately doped into the binary (Ca, Sr)ZnOS host, which partially occupy its Ca²⁺ sites and work as luminescent centers to give off stronger ML compared to when the same lanthanide-ion-dopant is doped into the unary-host of either CaZnOS or SrZnOS. Not only each lanthanide-ion-dopant in the binary host can separately give off efficient ML with a much lowered-pressure down to 2 N, but also ML colors can be easily tuned via changing the lanthanide dopant, such as green ML from Ca_0.66Sr_0.30ZnOS:Er_0.04, orange ML from Ca_0.66Sr_0.30ZnOS:Dy_0.04, red ML from Ca_0.66Sr_0.30ZnOS:Sm_0.04, and near-infrared ML from Ca_0.66Sr_0.30ZnOS:Yb_0.04. The lanthanide-ion-dopant-involved multicolor ML from binary (Ca, Sr)ZnOS hosts can be exploited for both stress sensing and anti-counterfeiting.