Mechanoluminescent (ML) materials play a significant role in modern technologies such as displays, artificial skin, and stress sensors, and are promising for devices that require no optical or electrical input for operation. However, only a limited range of ML emission colors are currently available.
In Advanced Materials, Prof. Bolong Huang of Hong Kong Polytechnic University, Prof. Dengfeng Peng from Shenzhen University, and Prof. Feng Wang from City University of Hong Kong, along with their co-workers, devise a general strategy for expanding the emission range of MLs.
ML materials are activated with lanthanide ions, which are integrated into oxysulfide crystals (CaZnOs) and exhibit intense ML displays from violet to the near-infrared region.
Under mechanical force, the ML materials accumulate surface charge via the triboelectric effect, which induces spatial charge separation and agglomeration, resulting in energy release in the form of photon emissions.
The lanthanum-doped ML phosphors, each exhibiting a unique color, can be used to generate encrypted anti-counterfeiting patterns. By writing across strips tagged with different ML materials, a sequence of color segments corresponding to the encrypted information could be extracted.
Prof. Bolong Huang: “We show bright multicolor ML emission from these doped CaZnOS phosphors with an intensity comparable to that of classical CZOS:Mn materials. The high-performance ML mechanism in this work, lanthanide-doped CaZnOS crystals, is investigated by density functional theory calculations. So, we also establish an approach to precisely manipulate the ML emission colors from green to red by adjusting the ratio of Tb3+– and Mn2+-doped CZOS phosphors. The availability of bright multicolor ML offers very promising future opportunities for bank anticounterfeiting and security applications.”