Heteroatoms-doped carbon dots: Fundamental, properties, coordination bonding and corrosion protection

Heteroatom-doping of carbon dots (CDs) has become an absolute necessity in material science due to their improved properties and applications. The literature review reveals that N and N,S-doped CDs are widely used as corrosion inhibitors. Heteroatoms directly participate in coordination bonding with the metallic substrates and/or increase CDs' electron-donating and withdrawing capabilities. Heteroatoms provide a strong bond with the metallic surfaces by improving CD frameworks' electron (charge) distribution feature and CDs' HOMO and LUMO capacities. The literature results indicate a relationship between doping and reducing the overall energy gap (ΔE: E_LUMO-E_HOMO), increasing reactivity and inhibitory potential. The presence of d-orbitals in the metals is anticipated to result in considerably better electron dispersion, increasing the corrosion inhibition potential of the metallic-doped CDs. The metallic heteroatoms can provide additional anticorrosive protection by passivating the metallic surface. The inhibition performance of HDCDs depends upon the doping heteroatoms, their relative percentages, the nature of metal and electrolyte, reaction timing and temperature time, the nature of precursors etc. This feature article comprehensively summarizes the advancements in using heteroatom-doped CDs (HDCDs) to prevent aqueous phase corrosion. A thorough literature review presents bonding features, opportunities, problems, and future perspectives regarding the corrosion protection effect of HDCDs.