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Zeolite molecular sieves: a new class of heat-induced delayed fluorescent materials with super-long fluorescence life.

In recent years, thermal delayed fluorescence (TADF) materials have become a hot topic in research because of its wide application prospects in optoelectronic devices, optical sensing and anti-counterfeiting.
However, the TADF materials reported are mainly organic materials and organic metal complexes, and their delayed fluorescence life is usually in the range of microseconds to a few milliseconds.
At the same time, because the triple excited state is easily quenched by oxygen, the luminescence of TADF materials is usually very sensitive to oxygen.
Therefore, the development of TADF materials with long delayed fluorescence life under new air conditions is of great significance in enriching the types of TADF materials and broadening the application fields of materials.

Jilin university has been working on the synthesis and preparation of the porous functional materials of zeolite.
The group put forward "quantum dots in zeolite molecular sieves (dots - in - zeolites)" synthetic strategy, through water/solvent hot synthesis method, the carbon points in situ confined in molecular sieve matrix, successfully developed a kind of brand-new with long delay fluorescence life TADF materials (figure 1).

Zeolite molecular sieves: a new class of heat-induced delayed fluorescent materials with super-long fluorescence life. 

The fluorescence quantum efficiency and the delayed fluorescence life of 350 ms can be displayed in the ambient air condition of the carbon point @zeolite composite material prepared by this method.
The nano-space limiting function of molecular sieve plays a key role in this unique TADF luminescence phenomenon, which can effectively limit the vibration of the functional groups on the carbon point surface and stabilize the triple excited state.
Material smaller singlet and triplet energy level difference (Δ EST) make electronic at room temperature can be realized from triply excited states to running jump between single excited states of the system, resulting in TADF photoluminescence.
In addition, the molecular sieve matrix can effectively block the oxygen in the air and avoid the quenching of the molecular oxygen in the triple excited state, so that the delayed fluorescence of the materials can be exhibited in the air environment.
The article also shows the application of materials in anti-counterfeiting (FIG. 2).
"Quantum dots in molecular sieves synthesis" concept for the design research and development with unique performance TADF material provides a new train of thought, the synthetic strategy can also be applied to other types of substrate materials, nano fluorescent material and subject to its in optoelectronic devices, biological imaging applications such as opened up a new perspective.
Zeolite molecular sieves: a new class of heat-induced delayed fluorescent materials with super-long fluorescence life. 

The research was published in Science Advances. Liu jiancong, a doctoral student at jilin university, was the first author and professor li yanyang was the co-writer.
The publication of this paper has attracted the attention of domestic and foreign counterparts.
C&EN of the American chemical society (ACS) reported on "A new record for delayed fluorescence" [1].
The royal institute of physics (IOP) its website NanotechWeb report titled "Carbon dots @ zeolites glow for longer" [2], besides emphasize long delay fluorescence life, also praised the paper put forward the "quantum dots in molecular sieve" strategy is quite simple and general, the preparation of TADF materials can be used for a variety of practical application.

The study was supported by national key research and development programs, the national natural science foundation program and the "111" program.