Development of fluorine-free fluorescent coatings with carbon dots and silica for superhydrophobic aluminum alloy surfaces

Abstract Superhydrophobic surfaces attract increasing attention, and they have been widely studied because of their excellent anti-icing, anti-corrosion, self-cleaning, and oil-water separation properties. In this study, a robust hierarchical structure was prepared on an Al-alloy substrate by spraying a mixture of epoxy resin (EP), hydrophobic SiO2, and styrene-ethylene-butyrene-styrene (SEBS) to realize superhydrophobicity. In addition, carbon dots (CDs) with fluorescence were incorporated to detect micro-coating damage in practical applications. The as-prepared superhydrophobic surface of EP-Si@CDs exhibited a high water contact angle of ~165.2° and a low sliding angle of ~7.6°, in addition to good non-wettabilities toward common liquid droplets. The superhydrophobic EP-Si@CDs surface was characterized using scanning electron and laser scanning confocal microscopy, energy-dispersive X-ray and X-ray photoelectron spectroscopy to investigate its structure and chemical composition. Meanwhile, superhydrophobic EP-Si@CDs displayed good durability, with the contact angle remaining at >150° and the sliding angle remaining at <10° after dragging for 280 cm under a mass of 100 g. Owing to the incorporation of the CDs, EP-Si@CDs emitted a bright yellow fluorescence under ultraviolet light, which could be used to detect micro damage. EP-Si@CDs exhibited excellent anti-icing and self-cleaning performances, and the related mechanisms were investigated in detail.