Chapter 6: Carbon Dots as Corrosion Inhibitors: Synthesis, Molecular Structures and Corrosion Inhibition

Carbon dots (CDs) are nanosized structures with luminescent properties, which were first reported as part of single-walled carbon nanotubes. CDs are considered a zero-dimensional (0D) carbon-dominated nanomaterial and consist of two main parts: a carbon skeleton and functionalized shell. The possibility of increasing the number of surface groups, such as carboxyl, hydroxyl and amine, improves water solubility and modifies the corrosion inhibition properties of CDs. These advantages can provide the desired properties to enhance corrosion inhibition. Inhibiting molecules must contain functional groups with electron donating atoms, p-type molecular orbitals, aromatic rings and unsaturation in order to favor adsorption on metallic surfaces. As such, CDs can be doped or functionalized, as described in several papers. Methods to obtain CDs are classified as a function of the starting material. Methods that involve breaking down large carbon structures into smaller ones are called top-down techniques, while those in which nanosized structures are obtained, progressing from smaller to larger molecules, are known as bottom-up methods. Methods to obtain corrosion inhibitors are mostly bottom-up, with an additional step to increase the presence of surface groups that can effectively improve CD properties, such as solubility and electron density, which are particularly important in corrosion inhibition.