A General Strategy for Developing Ultrasensitive "Transistor-like" Thermochromic Fluorescent Materials for Multilevel Information Encryption.

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 was proposed, which employed polarity-sensitive fluorophores with 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 w ere systematically studied for the first time. Benefiting from the above design, the obtained TFMs exhibited over 9500-fold fluorescence enhancement toward the temperature change, as well as ultrahigh relative temperature sensitivity up to 80% K -1 , which w ere first confirmed. Thanks to the superior transducing performance, the above-prepared TFMs could 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-switch-type fluorescent probes with ultrahigh conversion efficiency. This article is protected by copyright. All rights reserved.