Efficient UV-shielding coatings with carbon quantum dots

Most polymers are susceptible to ultraviolet (UV) radiation, showing irreversible damage after extended exposures, which consequently affects the durability of paints. The currently used inorganic UV protective compounds struggle to remediate this problem due to their short UV absorption range and poor photostability, resulting in the deterioration of the polymeric coatings. Recently, carbon quantum dots (CQDs) have been raising great interest owing to their excellent UV absorption and photostability with high compatibility in different polymeric systems, making them promising UV absorbers. The present work reports the synthesis of nitrogen-doped CQDs and their characterization by well-established techniques regarding their chemical composition, morphology, size, thermal stability, and optical properties. Different amounts of CQDs were incorporated in a commercial polyurethane (PU)-based matrix. The UV-shielding capacity, and chemical and mechanical properties of the developed coatings were evaluated. The present study reports the preparation of 40 μm thick CQDs@PU coatings with a high UV-shielding capacity of up to 98% under direct sunlight. Also, the prepared coatings were revealed to be resistant to abrasion and have good washability and adhesion to the metallic substrate.