Fig. 1

Characterization of GS-CDs under different synthesis conditions. a TEM images of the prepared GS-CDs@3 h, GS-CDs@5 h, GS-CDs@6 h, and GS-CDs@10 h samples, respectively, where the HRTEM images inserted in the upper right corner show the crystal lattices of the four GS-CDs. The scale bars were 20 nm. b UV absorption spectra of the prepared GS-CDs@3 h, GS-CDs@5 h, GS-CDs@6 h, and GS-CDs@10 h samples, where the insets show the photos of the four GS-CDs under sunlight (left) and UV light at 365 nm (right). c Contour maps showing the three-dimensional fluorescence spectra of GS-CDs@3 h, GS-CDs@5 h, GS-CDs@6 h, and GS-CDs@10 h, respectively. d Isometric projections of the three-dimensional fluorescence spectra of GS-CDs@3 h, GS-CDs@5 h, GS-CDs@6 h, and GS-CDs@10 h.