Electron-Beam-Induced Oligomerization of Perylene at the Surface of Perylene Single Crystals

Electron-beam (e-beam) irradiation provides a powerful strategy for inducing chemical reactions with high spatial selectivity. Herein, we demonstrate space-selective oligomerization of perylene molecules in single crystals under a low-vacuum scanning electron microscope. Mass spectrometry analysis of the reaction products reveals formation of perylene oligomers ranging from dimers to tetramers. Meanwhile, optical spectroscopy analysis of the products shows a redshift compared with that of the monomer, and a broad extinction band emerges beyond 800 nm after irradiation. The products also exhibit an intense near-infrared photoluminescence band centered at 720 nm upon 633 nm excitation. Raman spectroscopy combined with non-negative independent component analysis enables decomposition of the Raman bands into those arising from various reaction products. Using density functional theory calculations, one of the major oligomers is consistent with a perylene dimer with extended π-conjugation, called quaterrylene. Raster scanning of e-beam irradiation allows creation of dotted and textured patterns with a nanometer-scale (≈340 nm) resolution, yielding spatially controlled photoluminescent microstructures. This approach establishes a simple and versatile route for spatially resolved synthesis of π-extended PAHs and opens new possibilities for patterned organic emitters in microscale optoelectronic devices.