Stimuli-Responsive Emission from Hybrid Metal Halides

Stimuli-responsive photoluminescent (PL) materials have attracted considerable attention in recent years owing to their potential applications in anti-counterfeiting, information encryption, and sensing. Further investigations of the transformation mechanism and potential applications of stimulus-responsive PL materials are considerably important. In the current study, an organic–inorganic metal halide, C₉H₁₅N₃SbCl₅ ([C₉H₁₃N₃]²⁺ is a 1-(2-pyridyl) piperazine cation) is obtained, which exhibits a 0D structure with P-1 space group. At room temperature, when excited by UV light, the C₉H₁₅N₃SbCl₅ single crystals exhibit unimodal blue light emission at 405 nm, and grinding or hydrostatic pressure induces double-peak emissions at 405 and 650 nm. Interestingly, double-emission samples can be restored to single-emission samples by short annealing or storage in air for 2 weeks, and this process is reversible. Luminescence response to mechanical stimuli can also be achieved in the presence of hydrochloric acid and water. Spectral analysis and the analysis of the microstructural changes revealed that the structural modifications of the inorganic group play a pivotal role in the response to the stimulus. Finally, a composite film device based on C₉H₁₅N₃SbCl₅ is prepared to demonstrate the potential of these smart materials in anti-counterfeiting and sensing applications.