Fluorescent carbon dots for ratiometric detection of curcumin and ferric ion based on inner filter effect, cell imaging and PVDF membrane fouling research of iron flocculants in wastewater treatment

The CDs were used as the ratiometric probe for detection of curcumin and Fe3+. The fluorescence of CDs at 420 nm was quenched through inner filter effect (IFE) while the fluorescence of curcumin at 525 nm was enhanced after adding curcumin. The value of ln(I-525/I-420) increased linearly with the curcumin concentration in the range of 5-30 mu M, the limit of detection was 21.79 nM. After adding Fe3+ into the system of CDs-curcumin, curcumin complexed with Fe3+ leading to the quenching of the fluorescence of curcumin at 525 nm, which declined the spectra overlap between curcumin and CDs. The process of IFE was inhibited, the fluorescence of CDs at 420 nm was recovered. The value of ln(I-525/I-420) linearly decreased with the increasing of Fe3+ in the range of 2-14 mu M, the limit of detection is 18.11 nM. The CDs-curcumin system was successfully applied for H1299 cell imaging and has potential applications in the fields of fluorescent labeling and inhibition of tumor cells. The CDs-curcumin system was furtherly used for PVDF membrane fouling research of iron flocculants in wastewater treatment.