Thermally Activated Delayed Fluorescence of Fluorescein Derivative for Time-Resolved and Confocal Fluorescence Imaging

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• 作者：Xiaoqing Xiong ; Fengling Song ; Jingyun Wang ; Yukang Zhang ; Yingying Xue ; Liangliang Sun ; Na Jiang ; Pan Gao ; Lu Tian ; Xiaojun Peng
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 9, 2014
• 年：2014
• 卷：136
• 期：27
• 页码：9590-9597
• 全文大小：405K
• ISSN：1520-5126

文摘

Compared with fluorescence imaging utilizing fluorophores whose lifetimes are in the order of nanoseconds, time-resolved fluorescence microscopy has more advantages in monitoring target fluorescence. In this work, compound DCF-MPYM, which is based on a fluorescein derivative, showed long-lived luminescence (22.11 渭s in deaerated ethanol) and was used in time-resolved fluorescence imaging in living cells. Both nanosecond time-resolved transient difference absorption spectra and time-correlated single-photon counting (TCSPC) were employed to explain the long lifetime of the compound, which is rare in pure organic fluorophores without rare earth metals and heavy atoms. A mechanism of thermally activated delayed fluorescence (TADF) that considers the long wavelength fluorescence, large Stokes shift, and long-lived triplet state of DCF-MPYM was proposed. The energy gap (螖E_ST) of DCF-MPYM between the singlet and triplet state was determined to be 28.36 meV by the decay rate of DF as a function of temperature. The 螖E_ST was small enough to allow efficient intersystem crossing (ISC) and reverse ISC, leading to efficient TADF at room temperature. The straightforward synthesis of DCF-MPYM and wide availability of its starting materials contribute to the excellent potential of the compound to replace luminescent lanthanide complexes in future time-resolved imaging technologies.