The surface morphologies of the cotton fabrics before and after treatment were examined by SEM. Fig. 4a clearly shows the furrows and fibrils on the pristine cotton due to the inherent characteristic of the cotton fiber. From Fig. 4b, it is obvious to see that the cotton fiber treated with hydrolyzed HDTMS alone was relatively smooth because of the self-assembly of alkylsilanes on the surface of the cotton fiber. In comparison, as shown in Fig. 4c, the cotton fabric treated by the silica hydrosol was quite densely covered with the SiO2 nanoparticles, making the surface rougher. From the high magnification SEM image (Fig. 4d), it could be observed that the silica nanoparticles were felted each other, due to the cross-linking of the silica nanoparticles during the thermal curing of the cotton fabric coated by the SiO2 hydrosol. The uniform distribution of SiO2 nanoparticles with the diameter of 130–140 nm could be also seen from the image Fig. 4d. It is clear that the result is in accordance with the size and distribution of SiO2 nanoparticles measured by Nano Particle Size Analyzer. Fig. 4e and f demonstrates the cotton fabric treated by the silica hydrosol A2 together with HDTMS modification at different magnifications. From Fig. 4f, some ceraceous matters appeared on the particulate surface of the cotton fabric, likely caused by HDTMS modification. Hydrolyzed HDTMS was chemically bonded with SiO2 particles on the cotton fiber by surface condensation reaction, resulting in the formation of ceraceous matters with nanoparticles.