Time-Dependent Afterglow from a Single Component Organic Luminogen.

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Organic luminogens with long-persistent luminescence are crucial for applications like anticounterfeiting and bioimaging.
• Time-dependent color-tunable afterglow in single-component materials remains a significant research challenge.

Purpose of the Study:

• To report a novel organic luminogen, benzoyleneurea (BEU), with time-dependent afterglow.
• To investigate the mechanisms behind multiple persistent room-temperature phosphorescence (p-RTP) and thermally activated delayed fluorescence (TADF) emissions in BEU single crystals.

Main Methods:

• Synthesis and characterization of benzoyleneurea (BEU) and its derivatives.
• Single-crystal X-ray diffraction analysis to understand molecular packing and intermolecular interactions.
• Photoluminescence spectroscopy to study emission properties, including lifetimes and decay rates of p-RTP and TADF.

Main Results:

• BEU single crystals exhibit multiple p-RTP emissions with long lifetimes (369–754 ms) and shorter TADF (~1.2 ms).
• The distinct decay rates of p-RTP emissions result in observable time-dependent afterglow and color variation.
• The clustering-triggered emission (CTE) mechanism explains the multiple emission pathways, influenced by molecular structure and intermolecular interactions.

Conclusions:

• BEU is a promising single-component organic material for time-dependent, color-tunable afterglow applications.
• The observed phenomenon is attributed to the unique molecular structure facilitating divergent intermolecular interactions and the CTE mechanism.
• BEU crystals show potential for advanced anticounterfeiting and information encryption technologies.