Fig. 4

PL emission spectra of the carbon dots (A) CD (B) NiCD and (C) CuCD with increasing concentration of bilirubin from 0.5–280 µM (λex = 350 nm). Dual linear plots of log of concentration of bilirubin (µM) with PL intensity of carbon dots (D) CD (E) NiCD and (F) CuCD in the ranges 0.5–10 µM and 10–280 µM. Photographs depicting the quenching of fluorescence of carbon dots (G) CD (H) NiCD and (I) CuCD with increasing concentrations of bilirubin under UV illumination.