Green synthesis of value-added nitrogen doped carbon quantum dots from Crescentia cujete fruit waste for selective sensing of Fe3+ ions in aqueous medium

Green synthesis of nitrogen-doped carbon quantum dots (N-CQDs) by one-pot hydrothermal synthesis was reported using Crescentia cujete fruit waste for the first time in this study. The spherical carbon dots obtained are loaded with carboxyl, hydroxyl and amino functional groups on their surface which make them highly dispersible in water and emit green fluorescent light under UV irradiation. The photoluminescence (PL) behaviour of N-CQDs is greatly reduced by Fe3+ ions because of strong excited state electron transfer. This fluorescent “turn-off” behaviour towards Fe3+ is highly selective and sensitive with a limit of detection (LOD) of 0.257 μM. The highly stable N-CQDs were also successfully used as promising fluorescent probes for the sensitive detection of Fe3+ ions in three real waters, namely, river water, laboratory water and tap water.