Blue, green, and red full-color ultralong afterglow in nitrogen-doped carbon dots.

Carbon dots (CDs) with tunable emission colors and multiple emission modes are highly desirable in advanced optical anti-counterfeiting. Some pioneering efforts to trigger additional long-lived emission modes, nevertheless, did not perfectly solve the issue of printability and color-tunability in practical applications. Herein, we developed an encapsulating-dissolving-recrystallization route for the synthesis of CD-based anti-counterfeiting inks, and accordingly realized blue, green, and red full-color afterglow emissions from these CD-based inks when printed on paper. The printed inks simultaneously possessed triple emission modes including fluorescence (FL), delayed fluorescence (DF), and room-temperature phosphorescence (RTP), among which the long-lived emissions (DF and RTP) could be selectively activated by using different excitation wavelengths. We believe that the proposed synthetic route in this work may promote the development of multicolor-encoded and multiple-mode-integrated optical anti-counterfeiting systems, and will expand the application of CD-based materials to the fields of sensing, photodynamic therapy and bio-imaging.