Blue to green fluorescence of carbon-dots from lignin residual liquid synthesized from hydrothermal method

Lignin residual liquid constitutes a complex macromolecular substance obtained through the alkaline delignification process applied to palm oil empty fruit bunches. This study investigates the potential utility of lignin residual liquid as a precursor for synthesizing carbon nanoparticles with fluorescence properties through heat treatment (hydrothermal method). To comprehensively characterize the samples, we employed FTIR spectroscopy, UV-Visible spectrophotometry, and UV-light observations. The FTIR analysis confirmed the presence of hydroxide functional groups, while the UV-Visible spectrum revealed minimal absorbance. Within the UV spectrum, we observed distinct peaks ranging from 300 to 420 nm, indicative of varied absorption features resulting from the highly alkaline conditions. Notably, when exposed to UV-light, the samples exhibited a vibrant green-neon coloration. These findings point to the emergence of diverse fluorescence properties as an outcome of this research endeavor.