Figure 10

(a) Spectral overlap of the normalized UV–Vis absorption bands for the Cr (VI) ions (dash black) and the synthesised N-CQDs (green line), and the excitation spectrum (λem = 420 nm) (red line) and emission spectrum (λext = 340 nm) (blue line) of the N-CQDs. (b) LOD and LOQ of N-CQDs.