Figure 2.

a) Absorption (red) and emission (orange, yellow) of PBI 1 as crystalline powder as well as an individual microcrystal at room temperature and absorption (black solid line) and fluorescence (gray solid line) spectra of PBI 1 in dichloromethane solution (c ₀=10⁻⁷  m) at 298 K. Photographs of crystalline powder (b,d; scale bar=1 cm) on a black surface and an individual microcrystal (c,e; scale bar=50 μm) on quartz of PBI 1 under ambient light (b,c) and upon UV irradiation (d,e) that were used for spectroscopic investigations.