Hydrothermal synthesis of carbon dots: Unveiling temperature effects on optical, structural, and agricultural performance

Herein, we report the impact of temperature variation on the properties of carbon dots (CDs) synthesized via the hydrothermal method using Myxopyrum smilacifolium. CDs were prepared at three different temperatures and characterized using a comprehensive set of techniques, including UV-Vis spectroscopy, Tauc plot analysis, photoluminescence (PL) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). UV-Visible spectroscopy revealed a broad absorption spectrum with a prominent peak at 240 nm, which indicate strong quantum confinement effects. Tauc plot analysis demonstrated temperature-dependent variations in bandgap energy, with higher bandgaps for CDs have higher synthesis temperatures. PL spectroscopy exhibited blueshift in emission as the synthesis temperature increased. FTIR analysis confirmed the presence of hydrophilic functional groups such as C=O and O–H and DLS measurements indicated particle sizes ranging from 6 to 8 nm. As synthesized CDs were applied as seed priming agents on mung bean plants to investigate their impacts on germination and its growth. It was found that CDs synthesized at higher temperatures promote significant root and stem growth in mung bean plants, likely due to enhanced nutrient uptake and stress tolerance. These findings highlight the potential of CDs as eco-friendly agricultural fertilizers and provide valuable insights into their multifunctionality for applications in optoelectronics and sustainable agriculture. • Carbon dots (CDs) were synthesized hydrothermally using Myxopyrum smilacifolium at varying temperatures. • Optical properties of CDs showed temperature-dependent bandgap and photoluminescence behaviour. • FTIR confirmed the presence of functional groups (C=O, O–H), and DLS revealed particle sizes of 6–8 nm. • CDs synthesized at higher temperatures enhanced root and stem growth in mung bean plants. • Findings support the potential of CDs as eco-friendly nanomaterials for sustainable agriculture and optoelectronic applications.