Nanosized ZnO/SiO2‑Based Amphiphobic Coatings for Stone Heritage Protection

Exploring and developing an efficient protective coating for precious stone heritages that have been exposed to sunlight and rain for a long time is crucial. The UV resistance properties of nano-ZnO are apparent. Nano-SiO2 has a stable chemical structure and is one of the main components of stone. This paper introduces the synergistic protective effect of ZnO nanoparticles (ZnO-NPs) and SiO2 nanoparticles (SiO2-NPs) on stone, which is novel in this field. The functional nanocomposite coating (FZS coating) was obtained by spraying the ultrasonic mixture of ZnO-NPs and SiO2-NPs, cross-linked with a silane coupling agent, and modified by fluorocarbon. Wettability and UV aging tests showed that the sandstone deposited by FZS coating had excellent amphiphobicity (water contact angle (WCA) > 160°, oil contact angle (OCA) < 140°). The hydrophobicity was almost changeless after 300 h of UV irradiation, indicating high UV absorption capacity and durability. Interestingly, the amphiphobicity remains unchanged after alternating treatments of temperature and humidity, expressing superior weathering stability. This facile functional coating has potential applications protecting outdoor stone heritages.