Green, sustainable, and economical synthesis of fluorescent nitrogen-doped carbon quantum dots for applications in optical displays and light-emitting diodes

Abstract

Fluorescent carbon quantum dots (CQDs) have attracted increasing attention in recent years because of their multiple benefits, including low toxicity, biocompatibility, simplicity of functionalization, eco-friendly production, and a wide range of applications. However, expensive precursors and manufacture, as well as a time-consuming procedure, limit their economical design, which must be addressed. We provide a straightforward, cost-effective, eco-friendly, and long-term synthesis method for fluorescent CQDs based on an affordable medicinal plant precursor such as Cissus quadrangularis. The nitrogen-doped CQDs produced had a homogenous size distribution (4–9 nm) and green fluorescent nature, as well as strong photo-stability, excellent water solubility, and a quantum yield of roughly 5%. The existence of a large fraction of sp2 and sp3-carbon groups, as well as other hydrophilic oxygen and nitrogen-containing groups, was confirmed. Potential fluorescence processes are also hypothesized. Furthermore, we report a successful demonstration of N-CQDs for possible and cost-effective applications in quantum dot-based optical displays and down-conversion green emissive light-emitting diodes.