Large area, nanoparticulate metal oxide coatings for consumer nanotechnologies

Large area coatings containing nanoparticulate metal oxides dispersed in polymers are manufactured at high speed (up to 200 m(2) /min.) by curtain- or cascade coating on flexible substrates near room temperature. Simultaneously coated multilayers, which may contain different metal oxides, show interesting new properties for industrial applications. Thick (40 mu m) coatings with rare-earth doped aluminum oxide nanoparticles have been commercialized for waterfast ink jet media which are dry to touch after printing, show photo-parity and are very stable towards water, light and environment if appropriate inks are used. Strong capillary forces due to nanoporosity allow instant ink-absorption. Experimental techniques used to develop these materials and results related to imaging parameters are discussed. Thin layers (1-10 mu m) of nanoparticulate, nanoporous TiO2 and LiMn2O4, dispersed in non-electroactive polymers such as polyethylene glycols, can be used as electrodes for rechargeable Li-ion batteries with very fast charge-discharge cycles and high power performance. The excellent ion-conducting properties of unsintered, nanoparticulate coatings of these metal oxides were unexpected and allow applications of temperature sensitive substrates and organic addenda. By coating very thin, almost or totally polymer-free layers of highly-porous, monodisperse aluminum-oxides with minimum particle size, display devices with improved optical efficiency were prepared. These layers have a low refractive index thus allowing for higher intensities of light emitted by organic electro-luminescers in OLED's and PLED's. This property is useful for mobile devices as phones and PDA's. A hitherto unknown, photo-catalytic chemical reaction of the classical green emitter tris-(8-hydroxychinolino)-aluminum (Alq(3)) has been discovered in coatings of such optically efficient devices after exposing them to daylight in air. An efficient blue-emitting species of Alq3 with another stereochemical structure was directly formed within these layers at room temperature by photolysis in ambient atmosphere. Interesting new applications of specially designed, large-area coated and transparent nanostructured matrices on flexible substrates for optical gas sensors are discussed in more detail in this paper.