Facile, Scalable Spray-Coating of Stable Emulsion for Transparent Self-Cleaning Surface of Cellulose-Based Materials

Cellulose-based materials are vulnerable to moisture and microorganisms and thus lose their original mechanical properties and durability; meanwhile, self-cleaning technique as a disruptive nanotechnology of waterproofing is attracting tremendous interest. Here, we develop a facile, cheap, and scalable "top-down" strategy to fabricate a transparent self-cleaning surface for cellulose-based materials by spray-coating a stable emulsion of nano-SiO2 particles. The nanoparticles are precisely synthesized at an average diameter of ∼110 nm via a sol–gel way and finely tailored with hydrophobic function by successive modification of poly(dimethylsiloxane) (PDMS) and (heptadecafluoro-1,1,2,2-tetradecyl)trimethoxysilane (17F). The modified nano-SiO2 particles well-distributed on the microscale rough surface of the cellulose-based materials by spray-coating to form a micro/nano two-tier structure to entrap air for water resistance, and thus build a superhydrophobic surface with static water contact angle (WCA) over 150° and dynamic contact angle less than 10°. The spray-coated superhydrophobic surface maintains the paper handwriting and wood texture, and holds their original mechanical properties when they are exposed to wet conditions, indicating a transparent waterproof coating built on the materials. Such coating also exhibits dust proof and antibio-adhesive behavior, which, integrated with light transparency and water repellency, positions a transparent self-cleaning surface capable of being applied in various environments where it resists water, dust, or microorganisms and even acid or alkaline impacts, and being potentially applied to a wider range of materials other than cellulose-based materials.