Carbon quantum dots obtaining from waste and determining their environmental impacts with a life cycle assessment approach

Nanomaterials have enormous potential in various technical applications due to their unique properties. In particular, the great potential of carbon quantum dots has attracted much attention in recent years due to their unique optical properties. Given their wide range of applications, the development of their large-scale synthesis is extremely necessary. From this perspective, hydrothermal synthesis has become the most popular method due to its simplicity, low cost, and high efficiency. On the other hand, biomass waste is emerging as a renewable, sustainable, and easily accessible carbon source for the production of CQDs. However, the CQDs produced from biomass usually have low quantum yields, and this problem is addressed by doping with other elements, especially nitrogen.In this study, the hydrothermal method is preferred for the synthesis of CQDs from horse chestnut and horse chestnut combined with EDTA as a doping agent. First, the hydrothermal method at 180°C for 4, 8, 16, and 24 hours was applied to produce CQDs from horse chestnut, and then horse chestnut combined with EDTA was used to produce nitrogen-doped CQDs under the same conditions. The obtained products were characterized by XRD, FT-IR, UV-Vis, and PL. It has been determined that CQDs produced from horse chestnut combined with EDTA showed better structural properties, especially under 8 hours of reaction time. Finally, Life Cycle Assessment (LCA) was carried out to assess the environmental impacts of the production for the optimum conditions.