Highly Efficient Aggregation-Induced Red-Emissive Organic Thermally Activated Delayed Fluorescence Materials with Prolonged Fluorescence Lifetime for Time-Resolved Luminescence Bioimaging

ACS Appl Mater Interfaces. 2020 Nov 18;12(46):51293-51301. doi: 10.1021/acsami.0c15936. Epub 2020 Nov 6.


Organic thermally activated delayed fluorescence (TADF) materials are emerging as potential candidates for time-resolved fluorescence imaging in biological systems. However, the development of purely organic TADF materials with bright aggregated-state emissions in the red/near-infrared (NIR) region remains challenging. Here, we report three donor-acceptor-type TADF molecules as promising candidates for time-resolved fluorescence imaging, which are engineered by direct connection of electron-donating moieties (phenoxazine or phenothiazine) and an electron-acceptor 1,8-naphthalimide (NI). Theoretically and experimentally, we elucidate that three TADF materials possessed remarkably small ΔEST to promote the occurrence of reverse intersystem crossing (RISC). Moreover, they all exhibit aggregation-induced red emissions and long delayed fluorescence lifetimes without the influence of molecular oxygen. More importantly, these long-lived and biocompatible TADF materials, especially the phenoxazine-substituted NI fluorophores, show great potential for high-contrast fluorescence lifetime imaging in living cells. This study provides further a molecular design strategy for purely organic TADF materials and expands the versatile biological application of long-lived fluorescence research in time-resolved luminescence imaging.

Keywords: aggregation-induced emission; fluorescence imaging; red emission; thermally activated delayed fluorescence (TADF); time-resolved luminescence imaging.

MeSH terms

  • Biocompatible Materials / chemistry*
  • Biocompatible Materials / metabolism
  • Biocompatible Materials / pharmacology
  • Cell Survival / drug effects
  • Fluorescent Dyes / chemistry*
  • HeLa Cells
  • Humans
  • Microscopy, Fluorescence
  • Naphthalimides / chemistry*
  • Oxazines / chemistry*
  • Quantum Theory
  • Spectrometry, Fluorescence
  • Temperature


  • Biocompatible Materials
  • Fluorescent Dyes
  • Naphthalimides
  • Oxazines
  • phenoxazine