Nanostructured mesoporous materials via electrospinning : principle concepts in the preparation of oxide nanofibers from different building blocks

摘要

Over the last decade electrospinning has gained considerable scientific interest as a method for the preparation of nanostructured inorganic materials. Electrospun metal oxide fiber mats are under investigation for applications as e. g. electrode materials in electrochemical devices, as heterogeneous catalysts or as active material in sensing devices. The efficiency of such devices is strongly influenced and controlled by the material´s porosity and pore structure.While the preparation of metal oxide fibers from sol-gel precursors is already widely used for oxides of numerous elements, the synthesis of such fibers using preformed, dispersed nanoparticles is less exploited and understood. Simultaneously, it was observed, that titania fibers prepared from preformed nanoparticles feature improved porosities compared to sol-gel-based fibers.[1]This thesis investigates the fundamentals of the preparation of oxide nanofibers from different building blocks, namely sol-gel precursors, preformed nanoparticles or a combination of both in order to establish a basic concept concerning electrospinning of inorganic materials. This concept focuses on the origin of mesoporosity which is frequently observed, when electrospun fibers are prepared from preformed nanoparticles, but which has not been understood so far.Nitrogen physisorption as a straightforward method to characterize mesoporosity was investigated concerning its applicability to electrospun fibers and the assessment of pore sizes and pore volumes in such fibers. Therefore, electrospun silica model materials were prepared from commercial Ludox nanoparticle dispersions and analyzed by nitrogen physisorption in detail. By means of these basic investigations a specific density functional theory (DFT) analysis method was selected as a standard method to analyze electrospun fibers and afterwards applied to fibers of several metal oxides. Using this methodology it was possible to compare the mesoporosity of electrospun fibers of several metal oxides for the first time.