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 CO and CN 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.