Unlocking the potential of rice husk pyrolysis oil: Dual production of high-energy solid fuel and Fe²⁺ detecting carbon nanodots for environmental application

The urgent need for sustainable energy solutions and environmental monitoring necessitates innovative approaches to biomass utilization. This study explores unlocking the potential of rice husk pyrolysis oil for dual applications: producing high-energy solid fuel and environmentally sensitive carbon nanodots (B-CDs). Slow pyrolysis of rice husk oil, followed by atmospheric distillation, transforms the oil into bio-coal with a high calorific value of 29.85 MJ/kg, significant aliphatic and aromatic carbon content, lowest ash content, and abundant oxygen functional groups, making it a viable fossil fuel alternative. Further, oxidative crystalline cutting and surface modification of this bio-coal yield B-CDs that exhibit blue fluorescence with a quantum yield of 41 %, an average size of 3.4 nm, and excellent photostability and hydrophilicity. Notably, these B-CDs are self-doped with nitrogen on their surface, enhancing their functionality. They demonstrate high sensitivity for Fe²⁺ detection, with a limit of detection (LOD) of 0.34 μM over a linear range of 0–100 μM, and a strong response to alkaline conditions. Validation experiments in tap and seawater samples confirmed the practical environmental applications of B-CDs. This study not only contributes to the advancement of pyrolysis oil as a source of fuel energy but also emphasizes the production of valuable carbon nanomaterials for environmental application.