The surface of SiO2 nanoparticles synthesized by this process has numbers of hydroxyl groups. Therefore, the hydroxyl groups on the cotton fiber play a key role for the preparation of superhydrophobic cotton fibers surface (Li et al., 2008; Vince et al., 2006).However, as shown in Fig. 2a, owing to the existence of the natural plant wax layer (Schmutz, Jenny, & Ryser, 1994), the surface of raw cotton fiber was smooth, which made SiO2 nanoparticles not easy to attach to the fiber surface (Wang, Zheng, & Wang,2012). Hence, the removal of plant wax layer would be very necessary. As shown in Fig. 2b, after the pretreatment of raw cotton,many longitudinal corrugations and interspaces appeared on the cotton fiber surface, suggesting that the natural plant wax layer of the raw cotton fiber had been removed and hydroxyl groups was exposed to make the cotton fiber more hydrophilic. Moreover, the generation of the corrugations and interspaces made the SiO2 sol permeate the interspaces to generate SiO2 nanoparticles easily (Lim & Huang, 2007). In these interspaces, the SiO2 nanoparticles tightly adhered to the cotton fiber through the chemical bond bond interaction, which generated between the hydroxyl groups from cotton fiber and hydrolyzed silane. Fig. 2c shows that the single fiber was densely and uniformly covered by the SiO2 nanoparticles and the arrangement of SiO2 nanoparticles with diameter about 100 nm significantly strongly roughened the cotton surface. Finally, the cotton fiber coated by SiO2 nanoparticles was modified by the OTS reagent, and the wetting behavior of this cotton surface obtained a great improvement with the WCA of 156◦. By this OTS treatment, the hydroxyl groups produced from OTS hydrolysis reacted with the hydroxyl groups of SiO2 nanoparticles and cotton fibers, and thus the long-chain hydrophobic alkyls were introduced on the cotton fiber surface. With the combination of fiber surface roughness and a layer of low surface energy OTS film, the cotton could not be wetted by water droplets and exhibited the propertyof superhydrophobic.