Metal–Organic Framework Based Thermally Activated Delayed Fluorescence Emitter with Oxygen‐Insensitivity for Cell Imaging

Abstract

To achieve better resolution and contrast in fluorescence techniques, time‐resolved fluorophores are promising constituents for probes in imaging and sensing, allowing for the elimination of background signals from scattering and short‐lived autofluorescence. Here a metal–organic framework (MOF) named Spiro‐MOF‐1 is designed with high thermally activated delayed fluorescence (TADF) persistence using a strategy of high rigidity to achieve a lifetime more than two times longer than that of pure linker. The rigid structure originated from spiro‐bi‐acridine unit is unambiguously revealed through 3D electron diffraction tomography (3D‐EDT). Furthermore, nanocrystals of Spiro‐MOF‐1 are successfully developed and modified with polyethylene glycol (PEG) as a biocompatible, time‐resolved fluorescent fluorophore with high TADF persistence, which exhibits a lifetime around 1 μs with no obvious decay under various bio‐mimicking environments, which has not been achieved by any other MOF‐based TADF emitter and small organic molecules. In further cell experiments, PEG‐modified nanocrystals exhibit a fluorescent signal that is more than 30 times longer than that of autofluorescence background in BGC823 cell line.

Recent advances in the design of afterglow materials: mechanisms, structural regulation strategies and applications

“…MOFs, as metal-organic coordination polymers (MOCPs), provide many ways to improve the luminescence efficiency by controlling the multifunctional synergy of organic ligands and metal linkers at the molecular level. [265][266][267][268][269][270][271][272][273][274][275][276][277][278] In order to achieve long-lived TADF, NRD processes involving triplet annihilation of the emitter need to be suppressed by the host matrix. MOFs are ideal host matrices to inhibit NRD because of their porous structures that can accommodate and stabilize luminophore molecules.…”

“…MOFs, as metal–organic coordination polymers (MOCPs), provide many ways to improve the luminescence efficiency by controlling the multifunctional synergy of organic ligands and metal linkers at the molecular level. 265–278…”

“…8f). 269 The A–D–σ–D–A (SAC) structure was chosen as the linker, and unlike conventional organic linkers, the core C atom of SAC serves as a σ spacer that connects two orthogonal acridine planes without participating in the conjugation. A large torsion angle is formed between the two tightly bound acridine planes.…”

Transformational Modulation of Fluorescence to Room Temperature Phosphorescence in Metal–Organic Frameworks with Flexible C–S–C Bonds

“…Photoluminescent (PL) metal−organic frameworks (MOFs) have emerged as multifunctional materials with a wide range of applications, spanning sensing, 1,2 bioimaging, 3 anticounterfeiting, 4−6 and more. In recent years, significant advancements have been made in the development of PL MOFs, with primary research and applications centered around tuning PL colors, adjusting brightness, and sensor applications.…”

Organic Thermally Activated Delayed Fluorescence Host–Guest Nanoparticles for Super‐Resolution Imaging

“…In recent years, thermally activated delayed fluorescence (TADF) materials have attracted great attention in organic lightemitting diodes (OLEDs) and time-resolved imaging with the merits of high exciton utilization efficiency as well as long 𝜏. [12][13][14][15][16] On the one hand, TADF theoretically can reduce triplet accumulation through accelerating reverse intersystem crossing (RISC) process from a non-radiative triplet state (T 1 ) to a radiative singlet state (S 1 ) at room temperature, thereby decreasing optical losses caused by triplet absorption and singlet-triplet annihilation at high triplet exciton density. More importantly, the regenerated radiative singlet excitons through RISC are conductive to contribute population inversion for SE.…”