Research / 2021 / Article / Fig 4

Review Article

Afterglow Carbon Dots: From Fundamentals to Applications

Figure 4

(a) Schematic representation of the activation of the afterglow luminescence of CDs via covalent fixation effect. (b) Photographs of CDs@SiO2 mixture in dialysis against deionized water (upper row), an aqueous dispersion of CDs@SiO2 (middle row), and CDs@SiO2 powder (bottom row) with turn-on and turn-off of UV excitation at different delay times (adapted and copyright permission [46], American Chemical Society). (c) TEM image of nSiO2 covalently modified with CDs. (d) Photographs of the dispersion of CDs@nSiO2 and RhB solution with and intermediate removal of UV excitation (365 nm). (e) FT-IR profile of CDs, nSiO2, and CDs@nSiO2 (adapted and copyright permission [75] (c–e), American Chemical Society). (f) Schematic representation of the conversion of fluorescent CDs (F-CDs) to phosphorescent CDs (P-CDs) via high-temperature heating. (g) Photographs of P-CDs upon turn-on and turn-off of UV excitation. (h, i) TEM and HRTEM images of F-CDs. (j, k) TEM and HRTEM of P-CDs. (l) Normalized fluorescence (black curve) and phosphorescence (blue curve) profiles of P-CD powder and corresponding excitation spectra (red line for fluorescence at 461 nm, pink line for phosphorescence at 538 nm) (adapted and copyright permission [76] (f–m), Wiley-VCH Verlag GmbH & Co. KGaA).