Thin coatings based on organically modified alkoxysilanes, partially modified with nano-particles, are prepared following the sol-gel-technique. These coatings are applied to different fiber material, namely polyester, polyamide and glass fiber. The introduced coatings offer excellent barrier properties protecting fiber material against basic and acidic atmospheres, whereby the modification with nano-sized aluminum oxide particles improved the wear resistance of the sensitive glass fiber material in addition. Examples are given of water- and oil repellent or UV- absorbing finishings by modifying the sols with either low amounts of hydrophobic/oleophobic components or with certain nano-particles. The amorphous networks also allow the permanent incorporation of photochromic dyestuffs, that retain their ability for reversible color-shifts when irradiated with ultraviolet radiation, leading to photochromic textiles.