Photoinduced On and Off Polymeric Room Temperature Phosphorescence Based On Polycyclic Aromatic Hydrocarbon Isomers

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Polycyclic aromatic hydrocarbons like anthracene (Ant) and phenanthrene (Phe) are isomers used in organic optical and electronic materials.
• Despite structural similarity, Ant and Phe exhibit distinct photochemical and physical properties.

Purpose of the Study:

• To investigate and compare the room temperature phosphorescence (RTP) properties of polyvinyl alcohol (PVA) composites incorporating 9-anthraceneboronic acid (B-Ant) and 9-phenanthrenylboronic acid (B-Phe).
• To understand the influence of photostability on the RTP performance of organic phosphors under UV irradiation.

Main Methods:

• Synthesis of PVA-B-Ant and PVA-B-Phe via a B-O click reaction.
• Characterization of photophysical properties, including fluorescence (FL) and RTP emissions, and phosphorescence lifetimes.
• Experimental and theoretical calculations to analyze the behavior of Ant and Phe derivatives under UV light.

Main Results:

• PVA-B-Phe (1%) film displayed strong fluorescence at 374 nm and RTP at 523 nm with a 1.9 s lifetime and green afterglow.
• PVA-B-Ant (1%) film showed intense blue fluorescence at 414 nm, but its emission diminished significantly with prolonged UV irradiation.
• Photodimerization of Ant within the PVA matrix under UV light was identified as a competing process that hinders RTP.

Conclusions:

• Phenanthrene derivatives, when incorporated into PVA, exhibit robust RTP properties.
• Anthracene derivatives suffer from photodimerization under UV light, which suppresses RTP and indicates poor photostability.
• The photostability of organic phosphors is a critical factor influencing their RTP performance, particularly under UV exposure.