Self-Assembling Surfactant Aggregates for Synthesis of Nanomaterials

Abstract: The main objective of this thesis was to study how surfactant assemblies can be used as templates to form inorganic nanomaterials. Both water-in-oil microemulsions and liquid crystalline phases have been used as structure directing agents. Major focus has been on the formation of nanostructured silver and titanium oxide, but crystallisation of calcium carbonate has also been investigated. Most of the studies have been on how surfactants influence the morphology and crystallinity of the formed materials, but also the effect on the surfactants themselves has been investigated to some extent. Furthermore, the produced titania has been tested for photocatalytic activity and the effect of crystal structure and morphology on the activity has been studied.

It was found that water-in-oil microemulsions could be used as microreactors for the formation of both titania and silver nanoparticles. Two slightly different techniques were investigated. In the first a titanium alkoxide was hydrolysed at very low pH inside the microemulsion droplets forming titania. In the second method a non-ionic surfactant-based microemulsion was used as a combined structure directing agent and reducing agent giving rise to silver nanoparticles.

It is shown that a highly viscous liquid crystalline phase can be used for the formation of silver and calcium carbonate nanoparticles, as well as for the formation of mesoporous titania. Here three slightly different approaches were utilised. Non-ionic surfactants have been used as reducing agent for the combined formation and macroscopic alignment of silver nanoparticles, as templates for a controlled hydrolysis together with an evaporation induced surfactant self-assembly forming ordered mesoporous titania having a high crystalline content, and for calcium carbonate nanoparticle formation by letting a calcium chloride containing liquid crystal be subjected to carbon dioxide gas.

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