Green and Near-Infrared Dual-Mode Afterglow of Carbon Dots and Their Applications for Confidential Information Readout

Near-infrared(NIR),particularly NIR-containing dual-/multimode afterglow,is very attractive in many fields of application,but it is still a great challenge to achieve such property of materials. Herein,we report a facile method to prepare green and NIR dual-mode afterglow of carbon dots(CDs) through in situ embedding o-CDs(being prepared from o-phenylenediamine) into cyanuric acid(CA) matrix(named o-CDs@CA). Further studies reveal that the green and NIR afterglows of o-CDs@CA originate from thermal activated delayed fluorescence(TADF) and room temperature phosphorescence(RTP) of o-CDs,respectively. In addition,the formation of covalent bonds between o-CDs and CA,and the presence of multiple fixation and rigid e ects to the triplet states of o-CDs are confirmed to be critical for activating the observed dual-mode afterglow. Due to the shorter lifetime and insensitiveness to human vision of the NIR RTP of o-CDs@CA,it is completely covered by the green TADF during directly observing. The NIR RTP signal,however,can be readily captured if an optical filter(cut-o wavelength of 600 nm) being used. By utilizing these unique features,the applications of o-CDs@CA in anti-counterfeiting and information encryption have been demonstrated with great confidentiality. Finally,the as-developed method was confirmed to be applicable to many other kinds of CDs for achieving or enhancing their afterglow performances.

Enabling robust and hour-level organic long persistent luminescence from carbon dots by covalent fixation

The first carbon dot(CD)-based organic long persistent luminescence(OLPL)system exhibiting more than 1 h of duration was developed.In contrast to the established OLPL systems,herein,the reported CDs-based system(named m-CDs@CA)can be facilely and effectively fabricated using a household microwave oven,and more impressively,its LPL can be observed under ambient conditions and even in aqueous media.XRD and TEM characterizations,afterglow decay,time-resolved spectroscopy,and ESR analysis were performed,showing the successful composition of CDs and.CA,the formation of exciplexes and long-lived charged-separated states.Further studies suggest that the production of covalent bonds between CA and CDs plays pivotal roles in activating LPL and preventing its quenching from oxygen and water.To the best of our knowledge,this is a very rare example of an OLPL system that exhibits hourlevel afterglow under ambient conditions.Finally,applications of m-CDs@C.A in glow-in-the-dark paints for emergency signs and multicolored luminous pearls were preliminarily demonstrated.This work may provide new insights for the development of rare earth-free and robust OLPL materials.