Organic dopant cyclization and significantly improved RTP properties.

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Internal rotation in triplet-generating molecules hinders room temperature phosphorescence (RTP).
• Rigid microenvironments are typically used to mitigate this rotation.
• Pre-locking internal rotation units is a less-explored but potentially effective strategy.

Purpose of the Study:

• To investigate the impact of pre-locking internal rotation units on RTP.
• To design, synthesize, and characterize novel cyclized triplet-generating molecules.
• To develop ultralong RTP materials for applications in optical encryption and anti-counterfeiting.

Main Methods:

• Design and synthesis of a rotatable phenyl molecule (DIA) and its cyclized derivatives (CDIA, ODIA).
• Fabrication of polymer films (PMMA) doped with synthesized molecules.
• Characterization of RTP properties, including emission spectra and lifetimes.
• Investigation of Förster resonance energy transfer (FRET) for red afterglow development.

Main Results:

• Uncyclized DIA showed minimal RTP, while CDIA and ODIA exhibited ultralong green and blue RTP with lifetimes exceeding 2000 ms.
• The pre-locking strategy effectively suppressed internal rotation, enhancing RTP efficiency.
• Trace doping with perylene red enabled red afterglow materials with lifetimes up to 1800 ms via efficient FRET.
• Demonstrated preliminary applications in optical encryption and anti-counterfeiting.

Conclusions:

• Pre-locking internal rotation units is a potent molecular strategy for achieving ultralong RTP in polymers.
• Developed novel cyclized molecules (CDIA, ODIA) with significantly enhanced RTP properties.
• Established a pathway for creating multi-color ultralong afterglow materials for advanced applications.