Monofactorial control of carbon dot emission in solvent-free synthesis for wide-gamut light emitting diodes

The flexible regulation of carbon dots (CDs) emission wavelengths through controlling single variable remains a significant challenge. In this study, we present a novel single-factor tuning preparation strategy for synthesizing full-color fluorescent CDs in an open, rapid and solvent-free reaction system. Tunable purple-to-red emission CDs were prepared within 5 min solely by adjusting o -phenylenediamine/dicarboxylic acid mass ratios. The production yields and quantum yield of CDs can reach up to 70.5 % and 34.1 %, respectively. Changing the reactants ratio affects the dehydration and carbonization. This led to an orderly red-shift in CDs emission wavelength. Detailed characterizations and theoretical calculations reveal key insight. The transformation in optical features correlates with a gradient increase in particle size. It also correlates with an increase in graphitic nitrogen and sp 2 -conjugated domains. These CDs exhibit excellent biocompatibility and stable fluorescence characteristics, making them successful for bioimaging applications in live cells and zebrafish embryos. Furthermore, leveraging the simplicity and solvent-free nature of the synthesis, full-color and high color rendering index (CRI > 83) white light LEDs with tunable color temperature were successfully fabricated, demonstrating substantial application potential for commercial lighting. The proposed single-factor solvent-free synthesis strategy may further improve the industrialization potential of CDs-based optical materials.