Fluorescent N-doped carbon quantum dots: A selective detection of Fe3+ and understanding its mechanism

•Highly fluorescent carbon quantum dot with average size ∼ 3–6 nm have been synthesized successfully by simple methode.•The high fluorescence quenching ability towards heavy metal ions of Fe3+ was observed.•The average lifetime of (5.89648 ± 0.40) ns was calculated from TRPL decay curve.•Deep study on analysis of mechanism behind Fe3+ sensing.•The synthesized N-CQDs shows 80% photostability after 4 h continuous UV (365 nm) illumination.