Green synthesis of heteroatom-doped carbon quantum dots derived from Chenopodium Album for sustainable nanofertilization

Abstract

Nano-enabled sustainable agriculture is gaining traction, with carbon-based nanoparticles emerging as promising alternatives. This study highlights the successful green synthesis of heteroatom-doped carbon quantum dots (h-CQDs) enriched with multiple elements (N, Na, Mg, P, K, Ca). This study successfully synthesizes h-CQDs containing nitrogen, sodium, magnesium, phosphorus, potassium, and calcium from Chenopodium album (Bathua) leaf extract, without external doping precursors. Characterization through HRTEM, EDS, XRD, FTIR, UV–vis, and fluorescence spectroscopy confirmed that the CQDs exhibit a near-spherical morphology (3–5 nm, average 3.75 nm) with a predominantly amorphous structure. They demonstrate strong photostability, greenish fluorescence under UV light, and the presence of hydrophilic surface groups, which enhance their water suspension capabilities. As a nanofertilizer, h-CQDs were tested on mung bean (Vigna radiata) at concentrations of 0.2–10 mg/mL (200–10,000 ppm). While 0.2 mg/mL optimized plant growth, higher concentrations inhibited shoot elongation, reducing growth by 15% at 200 ppm, 21% at 1000 ppm, 63% at 5000 ppm, and 74% at 10,000 ppm. This study explored CQD application in agriculture beyond the commonly reported 100 ppm threshold. Overall, C. album-derived h-CQDs emerge as a promising, eco-friendly nanofertilizer that enhances plant growth while supporting sustainable agriculture.