Cool white, persistent room-temperature phosphorescence in carbon dots embedded in a silica gel matrix

Herein we report the observation of room-temperature phosphorescence from carbon dots (CDs) embedded in a silica gel matrix. The precursors used in the synthesis (malonic acid and ethylene diamine) were chosen to have the surface of the CDs rich in C[double bond, length as m-dash]O and C[double bond, length as m-dash]N functionalities. The CDs in an aqueous dispersion exhibit an intense blue fluorescence and upon incorporation into silica gel demonstrate a green after-glow, which is visible even to the naked eye. The phosphorescence measurements indicated that the life-time of phosphorescence emission is about 1.8 s, under 380 nm excitation, which is the highest magnitude reported for CDs in solid-state matrices. Moreover, the 1931 CIE color parameters corresponding to the phosphorescence emission are in the white gamut region of the chromaticity diagram.