High‐Temperature, Reversible, and Robust Thermochromic Fluorescence Based on Rb₂MnBr₄(H₂O)₂ for Anti‐Counterfeiting

Abstract

Thermochromic fluorescent materials (TFMs) characterized by noticeable emission color variation with temperature have attracted pervasive attention for their frontier application in stimulus‐response and optical encryption technologies. However, existing TFMs typically suffer from weak PL reversibility as well as limited mild operating temperature and severe temperature PL quenching. PL switching under extreme conditions such as high temperature will undoubtedly improve encryption security, while it is still challenging for present TFMs. In this work, high‐temperature thermochromic fluorescence up to 473 K and robust structural and optical reversibility of 80 cycles are observed in Rb2MnBr4(H2O)2 and related crystals, which is seldom reported for PL changes at such a high temperature. Temperature‐driven nonluminous, red and green light emission states can be achieved at specific temperatures and the modulation mechanism is verified by in situ optical and structural measurements and single particle transition. By virtue of this unique feature, a multicolor anti‐counterfeiting label based on a broad temperature gradient and multidimensional information encryption applications are demonstrated. This work opens a window for the design of inorganic materials with multi‐PL change and the development of advanced encryption strategies with extreme stimuli source.

A Robust Anti-Thermal-Quenching Phosphor Based on Zero-Dimensional Metal Halide Rb3InCl6:xSb3+

“…We also recorded XRD patterns at various temperatures during a heating–cooling cycle (Figures d and S4) from 298 to 523 K and back, by which we could verify that the sample remained structurally stable. In detail, the diffraction peaks gradually shifted to lower (higher) 2θ angles with increasing (decreasing) temperature, and returned to their initial position when cooling back to RT, without generating any impurity peaks. , Hence, the sample underwent a reversible lattice expansion-contraction with a slope of −1.9 × 10 –3 2θ/K –1 (Figures S4 and d). Overall, we can state that the Rb 3 InCl 6 : x Sb 3+ sample exhibited robust, both reversible luminescence stability and structural stability upon heating/cooling.…”

Designing Yolk–Shell Nanostructures for Reversible Water-Vapor-Responsive Dual-Mode Switching of Fluorescence and Structural Color

“…1−3 On account of their ionic nature and low formation enthalpies, they are sensitive to external stimuli such as water, oxygen, light, and heat. 4−6 This sensitivity has initiated the development of responsive MHPs, including hydrochromic, 7−9 thermochromic, 10,11 photochromic, 12,13 and mechanochromic ones. 14 Among them, water-stimulated MHPs fluorescence switches are deemed as most encouraging due to the low cost and environmental friendliness of the stimulus, as well as their application potential in areas such as anticounterfeiting, information encryption/decryption, and humidity sensing.…”

“…In the past decade, metal halide perovskites (MHPs) have become promising materials in the optoelectronic field due to their versatile optoelectronic properties and low-cost solution processability. − On account of their ionic nature and low formation enthalpies, they are sensitive to external stimuli such as water, oxygen, light, and heat. − This sensitivity has initiated the development of responsive MHPs, including hydrochromic, − thermochromic, , photochromic, , and mechanochromic ones . Among them, water-stimulated MHPs fluorescence switches are deemed as most encouraging due to the low cost and environmental friendliness of the stimulus, as well as their application potential in areas such as anticounterfeiting, information encryption/decryption, and humidity sensing. − However, the intrinsic instability of MHPs always leads to the irreversible degradation of the crystal framework when they are exposed to water.…”

Inorganic Salt Solution Assisted Grinding Synthesis of Stimuli-Responsive Perovskites for Reversible Information Encryption and Decryption Based on I Ching 64 Hexagrams

“…21,22 Furthermore, Liu's group investigated fascinating phase transitions within a Mn-based perovskite matrix, including Rb 2 MnCl 4 •2H 2 O, Rb 2 MnCl 4 , RbMnCl 3 , and Rb 3 MnCl 5 , and developed a multidimensional encryption strategy that employs high temperature as a key for decryption. 23 Zhang's team utilized hydrochromic Cs 3 Cu 2 I 5 and waterresistant Cs 3 Cu 2 I 5 @PMMA for anticounterfeiting purposes, effectively achieving multiple encryption effects. 24 These studies highlight the unique advantages of metal halide perovskites in stimuli-responsive luminescent materials.…”