Converting industrial waste into value: sustainable synthesis of carbon dots for catalytic and sensing applications

The development of multidisciplinary studies on highly integrated and industrial research-oriented skills and knowledge is now fundamental for technology innovation. For this reason, academic researchers particularly in the energy and industrial sectors, are focused on the management and analysis of complex systems. On this road, the objective of this research project has been achieved through the synergy between different scientific fields, which include chemistry, materials science, technology, and environmental issues, giving particular attention to aspects such as pollution and recovery of raw materials. In fact, the thesis presents a study focusing on sustainable development goals (SDGs) and an innovative valorization of industrial orange peel waste (OPW). The OPW were converted into carbon dots (CDs), nanoparticles with unique structural properties, and low toxicity, biocompatibility and stability. The developed synthesis method involves hydrothermal carbonization (HTC) and oxidative electrolysis, avoiding hazardous reagents and solvents, aligning with SDG12 (responsible consumption and production) and SDG13 (climate action). These CDs were employed to address water pollution (SDG6 and SDG14) and to promote new biocompatible industrial procedures replacing traditional harmful catalysts. Indeed, CDs were used in a electrochemical sensor, by modifying a screen printed carbon electrode, and as fluorescent probes demonstrating high sensitivity (limit of detection 0.013 μM and 14 μM respectively) for nitrobenzene detection in water media. Moreover, thanks to their intrinsic physicochemical and optical characteristics, the synthesized CDs successfully acted as reusable heterogeneous catalysts or photocatalysts in the Knoevenagel reaction, allowing to achieve high reaction yield in mild conditions.