Carbon dots as oxidant-antioxidant nanomaterials, understanding the structure-properties relationship. A critical review

Carbon dots (C-dots) are a large family of nanomaterials characterized by an intense photoluminescence. The origin of the emission is multifaceted and is dependent on a number of factors, including structure, surface, and composition. The term "carbon dots" is quite broad and encompasses a wide range of carbon nanostructures. The multiple properties are a result of this variability, which also makes it difficult to es-tablish a clear structure-property relationship. Photoluminescence is the property of this class of nano-materials that has garnered the greatest attention due to the possibility of applications in various fields, including biotechnologies, electronics, and energy. Another property of C-dots that has only lately been recognized is their antioxidant activity, i.e., the ability to act as a free radical scavenger. Furthermore, it has been proven that certain types of C-dots function as oxidizing agents when exposed to visible and/or UV radiation. This dual oxidant-antioxidant nature is particularly intriguing and closely related to the C-dot properties. Although many articles have been published on the subject, it still needs to be understood what structure-property relationships regulate the responses to free radicals. This review aims to provide a general overview of the characteristics of C-dots as scavengers or radical emitters by a critical analysis of the relevant studies. Based on their intended application as oxidants or antioxidants, the findings of this review can be used to synthesize C-dots with precisely defined functional properties.(c) 2023 Published by Elsevier Ltd.