Figure 6

Selective detection of Fe(III) and AA. (a) Schematic illustration of the PL response of CQDs to Fe(III) and CQDs/Fe to AA; (b) PL emission spectra (λex = 420 nm) of CQDs in the presence of Fe(III) with varying concentration; (c) comparison of PL intensity of CQDs in the presence of different metal ions; (d) Stern-Volmer plot for linear fitting of the PL intensity ratio versus the concentration of Fe(III) measured at 420 nm. Io and I are the emission intensities of CQDs in the absence and presence of Fe(III), respectively (e) PL spectra of the CQDs/Fe system showing the restoration of emission intensity on the addition of AA; (f) comparison of PL “turn-on” emission behavior upon the addition of different biomolecules to the quenched CQDs/Fe(III) system; (g) relationship between PL intensity restoration and AA concentration.