Turn-On fluorescence sensor based detection of heavy metal ion using carbon dots@graphitic-carbon nitride nanocomposite probe

We report a simple new approach on green synthesized carbon dots@graphitic-carbon nitride (CDs@g-C3N4) nanocomposite to explore the potential application of "Turn-On" fluorescent sensor for signaling the detection of multiple heavy metal ions. As prepared fluorescent CDs exhibits a high dispersibility and g-C3N4 nanosheets show a good exfoliation to strongly hold the CDs over its surface to constitute a label-free sensor. Initially, the fluorescence intensity of CDs was quenched via excited state non-radiative energy transfer process from CDs to gC(3)N(4) sheets. However, on hosting of metal ions into CDs@g-C3N4 nanocomposite it forms a strong surface complex with g-C3N4 nanosheets, which may encourage the recovery of CDs. More interestingly, the sensing performance was investigated at different pH to understand the switching in surface charge of g-C3N4 nanosheets, which has significantly improved the sensitivity for detection of Cr (VI), Cu (II) and Pb (II) ions with a LOD of 0.54 nM, 0.18 nM and 0.2 nM respectively. Moreover, this proposed sensor was expected to be prompt, convenient, low cost, an eco-friendly and sensitive platform for the detecting of heavy metal ions in practical samples with satisfying results.