Facile and green synthesis of highly fluorescent nitrogen-doped carbon dots from jackfruit seeds and its applications towards the fluorimetric detection of Au3+ ions in aqueous medium and in in vitro multicolor cell imaging

Abstract

Carbon dots (CDs) have drawn tremendous attention of researchers due to their excellent properties. Herein, we synthesized highly luminescent N-doped carbon dots (N-CDs) from jackfruit seeds used as a green carbon source by a facile, green and rapid one-step microwave-assisted method. The resulting N-CDs display excellent solubility in water, high photoluminescence (PL) quantum yield, QY (17.91%), high photostability, longer storage stability (stable up to more than 180 days without any agglomeration) and low cytotoxicity (90% upon addition of 0 to 2 mg mL⁻¹ of N-CDs) towards A549 cell line. In addition, the fluorescence of N-CDs is stable in a wide range of ionic strength and pH. The PL intensity of N-CDs was linearly, selectively and sensitively quenched by Au³⁺ ions. So we have demonstrated Au³⁺ sensing in aqueous media using N-CDs as the fluorophore and achieved a limit of detection of 239 nM. We also applied the obtained N-CDs as an effective fluorescent probe for in vitro multicolor cell imaging. In addition, we also synthesized gold nanoparticles (AuNPs) by using the strategy of reductive electron transfer between N-CDs and Au³⁺ ions.