Low‐Pressure‐Threshold Triggered Irreversible Emission Transformation toward Flexible Pressure Imaging and Information Encryption

Abstract Pressure‐driven irreversible emission transformation as an efficient means greatly facilitates the development of the rational structural design of high performance novel metastable states. However, the excessively required pressure can only be achieved by high‐pressure devices, significantly inhibiting practical applications. Here, we achieved an irreversible emission transformation in 0D copper halides (TPA)CuI 2 (TPA = Tetrapropylammonium) nanocrystals (NCs) via high pressure engineering, even at pressure as low as 0.6 GPa (approximately 6000 atmospheres). The large steric hindrance of organic cations (TPA + ) and enhanced hydrogen bonding increased the potential barrier of phase transition, resulting in an irreversibility. The quenched samples exhibited bright green emission after pressure treatment, greatly different from the initial dull white light. The (TPA)CuI 2 NCs‐based film can be utilized as flexible and water‐resistant pressure imaging that just required macroscopic pressure, such as stamping or writing. Furthermore, the different recovery time upon applying different pressures provides dynamic passwords and time‐sensitive intelligence——eliminating the false and retaining the true. This work develops a promising pressure‐sensing material which can be easily accessible in practical applications for schlagstelle inspection of pipeline inwall and anti‐counterfeiting.