One-step sol-gel preparation of ultralow-refractive-index porous coatings with mulberry-like hollow silica nanostructures

Abstract Nowadays, intense research efforts are directed toward the development of novel preparation high-quality ultralow-refractive-index coatings. Herein, we report a facile atmospheric process to fabricate ultralow refractive index porous coatings with mulberry-like hollow silica nanostructures. The coatings were fabricated by a one-step base-catalyzed sol-gel method using 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane (POTS) 2 and tetraethyl orthosilicate (TEOS) 3 as co-precursors. The ultralow-refractive-index coatings could be obtained without any pretreatment (such as HF etching on the glass substrates) or post-treatment (such as the calcination to remove template), which is why it is suitable for large-area processing. Compared with previous methods, the procedure of this technique is simpler and more environmentally friendly. The refractive indexes of the coatings could be adjusted from 1.08 to 1.17. The effect of POTS amounts on the refractive index of coatings was investigated. Specifically, a possible particle growth mechanism of the fluoro-containing hollow silica nanoparticles (FHSNs) 4 sols was proposed. Furthermore, the water-repellent properties were also investigated. The ultralow-refractive-index coatings with porous silica microstructures have the advantages of abundant porosity, thus, they are promising to find potential applications in energy-stored materials and porous medium.