High-Resolution Afterglow Patterning Using Cooperative Vapo- and Photo-Stimulation

Bright afterglow room-temperature phosphorescence (RTP) soon after ceasing excitation is a promising technique for greatly increasing anti-counterfeiting capabilities. The development of a process for rapid high-resolution afterglow patterning of crystalline materials can improve both high-speed fabrication of anti-counterfeiting afterglow media and stable afterglow readout compared with those achieved with amorphous materials. Here, the high-resolution afterglow patterning of crystalline materials via cooperative organic vapo- and photo-stimulation is reported. A single crystal of (S)-(-)-2,2'-bis(diphenylphosphino)-5,5',6,6',7,7'8,8'-octahydro-1,1'-binaphthyl [(S)-H₈-BINAP] doped with (S)-(-)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP] shows green afterglow RTP. Crystals of (S)-BINAP-doped (S)-H₈-BINAP changed to an amorphous state with no afterglow capability on weak continuous photoirradiation under dichloromethane (DCM) vapor. Photoirradiation induced oxidation of the (S)-H₈-BINAP host molecule in the crystal. The oxidized (S)-H₈-BINAP forms on the crystal surface strongly interacted with DCM molecules, which induces melting of the (S)-BINAP-doped (S)-H₈-BINAP crystal and trigger formation of an amorphous state without an afterglow capability. High-resolution afterglow patterning of the crystalline film is rapidly achieved by using cooperative organic vapo- and photo-stimulation. In addition to the benefit of rapid afterglow patterning, the formed afterglow images of the crystalline film can be repeatedly read out under ambient conditions without DCM vapor.