材料科学
光化学
光致发光
紫外线
荧光
单重态
系统间交叉
光电子学
化学
激发态
原子物理学
光学
物理
作者
Mingyu Xin,Xipao Chen,Longyue Zhang,Hailiang Yang,D. Guo,Yaoping Hu
出处
期刊:Small
[Wiley]
日期:2024-10-31
标识
DOI:10.1002/smll.202407170
摘要
Abstract It is attractive but challenging to develop carbon dot (CD) based materials with tunable thermally activated delayed fluorescence (TADF), especially in the long wavelength region. Here, by simply calcinating the mixture of m‐phenylenediamine and MgF 2 at 300–500 °C, a series of CDs@MgF 2 composites exhibiting yellow, white, and ultraviolet‐blue TADF with high photoluminescence quantum yields of up to 37.6% are prepared. Photophysical studies reveal that the yellow TADF with long lifetimes of 810–1106 ms originates from the surface emission centers of CDs, while the ultraviolet‐blue TADF with short lifetimes of 266–379 ms is related to the carbon core emission centers. The combination of yellow and ultraviolet‐blue TADF in a single material triggers dynamic afterglow with time‐dependent colors from white to yellow. The MgF 2 matrix offers multiple confinement of CDs through a rigid network, strong space constraint, and robust covalent/hydrogen bonding, thus preventing the triplet excitations from non‐radiative transitions. The electron‐withdrawing fluorine atoms induce substantial spin‐orbit coupling and reduce the singlet‐triplet energy gap, consequently facilitating the reverse intersystem crossing to enhance TADF efficiency. Importantly, the CDs@MgF 2 composites possess outstanding optical stability against water, organic solvents, strong acids, bases, and oxidants. The fascinating TADF features enable the successful demonstration of multilevel information encryption using CDs@MgF 2 .
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