Photoreversible On-Off Recording of Persistent Room-Temperature Phosphorescence

Photoreversible on-off recording of red persistent room-temperature phosphorescence (RTP) is demonstrated. Host-guest materials composed of a persistent phosphorescent guest (D), a photochromic guest (A), and an amorphous steroidal host show red persistent RTP with a lifetime longer than 1 s based on D. The red persistent RTP function is erased by ultraviolet irradiation and recovered by irradiation with green light. The reversible photocyclization and decyclization of A allows and prevents dual dipole-dipole energy transfer from the singlet and triplet states of D to the ground state of A, respectively. The occurrence and lack of dual dipole-dipole energy transfer trigger the deactivation and activation of red persistent RTP from D, respectively. In samples labeled by the recording material, the RTP function of a specific target can be selectively activated using green light irradiation and the movement of the target can be detected as red persistent emission signal without interference from the movement of other persistent phosphorescent species as well as excitation light scattering.