Development of new nanomaterials syntheses for mesostructured TiO2 and SiO2

Mesostructured materials is a class of materials within the concept nanomaterials andcharacterized by structural features on the length scale 2-50 nm. This group of materials isinteresting for several applications such as, membrane and separation technology, heterogeneouscatalysis, controlled release, adsorption of pollutants, solar energy conversion, electrode materialsetc. These materials can be prepared with a wide range of chemical compositions. The thesisfocuses on syntheses of mesostructured silica and titania.The interests for mesostructured materials is growing and the need for low cost large scaleproduction methods is becoming interestingly important. An alkaline silicate solution, also calledwaterglass, is a cheap silica source that has been studied for this purpose. Mesostructuredmaterials are formed using a structure directing supramolecular assembly as template. These areeither based on surfactants or block-copolymers and for a large scale application, nonionicamphiphiles are desired. Synthesis methods for mesostructured silica require tuning theconditions for inducing the gelation of the silica monomers within the amphiphilic liquid crystaltemplate. The gelation behavior of water glass has therefore been studied by adjusting pH orsolvent evaporation and found to be fundamentally different for this. Following this a study ofthe liquid crystal formation of waterglass and nonionic surfactant mixtures has been examinedand the first direct synthesis of mesostructured silica from alkaline water glass and non-ionicblock-copolymers developed.Titanium dioxide is a photoactive semiconductor in its crystalline state. Mesoorderedcrystalline titania is desired in photovoltaic and photocatalytic applications. However, titanianormally crystalises through solid state reactions at several hundred degrees centigrade, whereasliquid crystals that are used for templating mesoorder exist at much lower temperatures asaqueous mixtures. A low temperature microemulsion synthesis of nanoparticulate crystallinetitania was developed and further modified into a new direct synthesis methodology for thepreparation of mesoporous titania with hexagonal mesostructure and with walls of tunablecrystallinity and crystallite size