Time-dependent phosphorescence from carbon dots enables multidimensional photoactivated printing and tunable molecular calculations

Room temperature phosphorescence (RTP) materials exhibit fascinating optical properties with great potential for various applications in the fields of luminescent displays and information encryption. However, most afterglow materials rely on pre-processing techniques such as molding and inkjet printing, greatly limiting the portability of their applications. In this study, we propose a reversible photoactivated phosphorescent anti-counterfeiting material. A dynamic photo-printable afterglow film that can be naturally erased was developed by doping carbon dots (CDs) of ofloxacin into polylactic acid (PLA). The material exhibits a 15 s yellow-to-green dynamic afterglow, while the lifetime of the material jumps from 2.5 ms to a maximum of 625 ms under continuous UV irradiation for less than 60 s. Characterization results showed that dynamic RTP originated from external oxygen-containing functional groups and internal nitrogen heterocycles with different decay rates within CDs. Further studies suggested that photoactivation properties should be attributed to the highly oxygen permeable but UV responsive structure of PLA. While oxygen in the membrane was excited by UV light, cross-linking occurs between PLA molecules, providing a rigid environment for CDs and limiting the subsequent entry of oxygen, further extending its lifetime. Based on the above advantages, this dynamic afterglow material has been successfully applied in light-emitting displays and optical molecular logic operation unit design.