Smart films based on semiconductor heterojunctions of mechanoluminescent sulfide and sulfur oxide for stress sensing and anti-counterfeiting applications

Mechanoluminescent (ML) materials offer significant potential for remote stress sensing and distribution. However, creating highly sensitive and responsive ML materials remains a challenge. In this study, mechanoluminescent semiconductor materials have been successfully prepared as Mn2+ doped ZnS-SrZnOS heterojunction composites. These materials exhibit high-resolution stress distribution visualization and rapid response, captured via camera recording. Notably, they possess a low stress triggering threshold, reaching the KPa level, and respond within milliseconds. Furthermore, it was found that by adjusting the doping concentration of Mn2+ within the heterojunction, the material utilizes its bimodal emission capability to manipulate the fluorescence shift and achieve optical anti-counterfeiting. The synthesis of smart films by combining the material with polydimethylsiloxane matrix had enabled the achievement of collision detection, information hiding and optical anti-counterfeiting. These results suggest that the prepared smart films have wide range of optical sensing applications.