Figure 1

(a) Survey XPS spectrum of the GQDs quantifying the amount of C (61.9%), N (18.9%) and O (19.2%). (b) C1s XPS spectrum of the GQDs revealing C-C, C-O and C-N bonds. (c) Raman spectrum of the GQDs dispersed in water (black trace) and of water (red trace). (d) HRTEM image (left) of one GQD and the corresponding Fast Fourier Transform (right).