title: Thermally activated delayed fluorescence of fluorescein derivative for time-resolved and confocal fluorescence imaging.
abstract: 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 μs 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 (ΔEST) 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 ΔE(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.
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology , 2 Linggong Road, Dalian 116024, People's Republic of China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Xiong
authors.forename: Fengling
authors.initials: F
authors.lastname: Song
authors.forename: Jingyun
authors.initials: J
authors.lastname: Wang
authors.forename: Yukang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yingying
authors.initials: Y
authors.lastname: Xue
authors.forename: Liangliang
authors.initials: L
authors.lastname: Sun
authors.forename: Na
authors.initials: N
authors.lastname: Jiang
authors.forename: Pan
authors.initials: P
authors.lastname: Gao
authors.forename: Lu
authors.initials: L
authors.lastname: Tian
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Peng
mesh_terms: D019793:Fluorescein / Q000138:chemical synthesis / Q000737:chemistry*; D005453:Fluorescence; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D057054:Molecular Imaging; D015394:Molecular Structure; D013696:Temperature; D013997:Time Factors
chemical_list: D019793:Fluorescein