A General Strategy for Developing Ultrasensitive “Transistor‐Like” Thermochromic Fluorescent Materials for Multilevel Information Encryption

Abstract Thermochromic fluorescent materials (TFMs) exhibit great potential in information encryption applications but are limited by low thermosensitivity, poor color tunability, and a wide temperature‐responsive range. Herein, a novel strategy for constructing highly sensitive TFMs with tunable emission (450–650 nm) toward multilevel information encryption is proposed, which employs polarity‐sensitive fluorophores with donor–acceptor–donor (D–A–D) type structures as emitters and long‐chain alkanes as thermosensitive loading matrixes. The structure–function relationships between the performance of TFMs and the structures of both fluorescent emitters and phase‐change molecules are systematically studied. Benefiting from the above design, the obtained TFMs exhibit over 9500‐fold fluorescence enhancement toward the temperature change, as well as ultrahigh relative temperature sensitivity up to 80% K ⁻¹ , which are first confirmed. Thanks to the superior transducing performance, the above‐prepared TFMs can be further developed as information‐storage platforms within a relatively narrow interval of temperature variation, including temperature‐dominated multicolored information display and multilevel information encryption. This work will not only provide a novel perspective for designing superior TFMs for information encryption but also bring inspiration to the design and preparation of other response‐switching‐type fluorescent probes with ultrahigh conversion efficiency.