Crystal induced phosphorescence from Benz(a)anthracene microcrystals at room temperature

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Pure organic phosphorescent materials at room temperature are exceptionally rare in scientific literature.
• Benz(a)anthracene (BaA) is a polycyclic aromatic hydrocarbon with limited reported phosphorescence under ambient conditions.

Purpose of the Study:

• To achieve efficient room-temperature phosphorescence from Benz(a)anthracene (BaA).
• To investigate the role of aggregation and morphology in inducing phosphorescence in organic compounds.

Main Methods:

• Synthesis of aggregated BaA hydrosols using a re-precipitation method with sodium dodecyl sulfate (SDS) as a morphology-directing agent.
• Characterization of particle morphology via optical microscopy and scanning electron microscopy (SEM).
• Photophysical property analysis using UV-vis absorption, steady-state, and time-resolved fluorescence spectroscopy.

Main Results:

• Efficient phosphorescence emission was observed from aggregated BaA hydrosols at room temperature, characterized by large Stokes-shifted structured emission.
• The observed phosphorescence is attributed to the rigidification effect induced by restricted intermolecular motions (RIM) within the aggregated crystalline state.
• Computational studies, including the second-order Fukui parameter, supported a parallel slipped conformation of neighboring BaA molecules within the aggregates.

Conclusions:

• Aggregation of Benz(a)anthracene (BaA) into hydrosols effectively induces room-temperature phosphorescence.
• Restricted intermolecular motion within the crystalline aggregates is the key mechanism for achieving phosphorescence.
• This work presents a novel approach to developing organic phosphorescent materials from readily available compounds.