Fig. 5. (A) The fast crystallization process of the model molecule (PBA-MeO) under ambient conditions over time. To shorten the crystallization time, concentrated solutions in highly volatile acetone were used (a larger image and fluorescence photo are shown in Fig. S39 and S40,† the video is in the ESI.† The photos and video were taken in the bright field by a 10× lens, Olympus IX71); (B) photographs of crystals grown by the slow evaporation of the acetone solution (PBA-MeO) under ambient light (top) and UV light (bottom); (C) fluorescence and phosphorescence spectra of the PBA-MeO powder crystals and ground sample; (D) XRD patterns of the two states, insets showing photographs of PBA-MeO crystals (top) and ground sample (bottom) taken under 254 nm UV light (left) and just after stopping UV light (right); (E) the stacking mode corresponding to the sharp diffraction peak located at 23.63° as assumed, the dashed blue lines representing H-bonds. (F) Demonstration of boron-containing phosphor-encoding for security documents with (t)PBA-MeO, (t)PBA-Cl and (t)PBA-Br before and after heating; (G) rooster pattern printed with PBA-MeO for 3 cycles; (H) panda pattern printed with PBA-MeO for 8 cycles.