Fast and Reversibly Humidity-Responsive Fluorescence Based on AIEgen Proton Transfer

Abstract

The construction of humidity-responsive fluorescent materials with reversibility, specificity, and sensitivity is of great importance for the development of information encryption, fluorescence patterning, and sensors. Nevertheless, to date, the application of these materials has been limited by their slow response rate and nonspecificity. Herein, a humidity-responsive fluorescence system was designed and assembled to achieve a rapid, reversible, and specific moisture response. The system comprised tetra-(4-pyridylphenyl)ethylene (TPE-4Py) as a fluorescent proton acceptor with an aggregationinduced emission (AIE) effect and poly(acrylic acid) (PAA) as a proton donor with an efficient moisture-capturing ability. The fluorescence color and intensity rapidly changed with increasing relative humidity (RH) because of TPE-4Py protonation, and TPE-4Py deprotonation resulted in recovery of the original fluorescence color in low-humidity environments. The proton transfer between the pyridyl group in TPE-4Py and the carboxyl group in PAA was reversible and chemically stable, and the humidity-responsive fluorescence system showed a high response/recovery speed, an obvious color change, good reversibility, and an outstanding specific moisture response. Because of these advantages, diverse applications of this humidity-responsive fluorescence system in transient fluorescent patterning and the encryption of information were also developed and demonstrated.

Super Adhesive Fluorescent Materials for Encrypted Messages, Underwater Leak Repair, and Their Potential Application in Fluorescent Tattoos

“…Aggregation‐induced emission (AIE) is a phenomenon in which materials exhibit intense luminescence upon forming aggregates due to restricted intramolecular motion. [ 10,11 ] Materials possessing AIE properties are ideally suited for solid‐state light‐emitting materials. Moreover, research on aggregation‐induced luminescence has attracted considerable attention since Tang discovered it in 2001.…”

Light and Humidity Dual-Responsive Anti-Counterfeiting Films Based on Hydrogen-Bonded Cholesteric Liquid Crystal Polymers with Spiropyran

“…25 They undergo reversible intramolecular bonding 26 and breaking when exposed to UV visible light 27 or heat, 28 transitioning between the merocyanine 29 (MC) and colorless SP forms. 30 This material 31 is easily synthesized and exhibits fluorescence under UV light, 32 making it a popular choice for anti-counterfeiting measures. 33 Hydrogen-bonded cholesteric liquid crystal 34 (HBCLC) polymers combine the helical structure of cholesteric liquid crystals 35 with the flexibility of polymer networks, 36 responsive color adjustments.…”

“…Spiropyran (SP) and its derivatives offer an ideal solution for our purpose . They undergo reversible intramolecular bonding and breaking when exposed to UV visible light or heat, transitioning between the merocyanine (MC) and colorless SP forms . This material is easily synthesized and exhibits fluorescence under UV light, making it a popular choice for anti-counterfeiting measures …”