Influences of Morphology and Doping on the Photoactivity of TiO₂ Nanostructures

Compared to the bulk, the nanoscale provides special characteristics for the functional materials. Moreover, the nanostructural morphology has also distinct influences. Enormous efforts have been devoted to the research of TiO₂ material, which has led to many promising applications. Beside the morphology impact, doping of titanium dioxide nanostructures by pristine metal nanoparticles (e.g. Ag, Pt, … etc.) revealed distinct improvement in the photocatalytic activity. Although the doping process can remarkably improve the photoactivity, it has also noticeable influences on the crystal structure. In this chapter, the important parameters affecting the photocatalytic activity of TiO₂ are discussed; morphology and silver doping. Also, effect of sliver-doping on the crystal structure and the nanofibrous morphology is investigated. Moreover, the influence of the temperature on the photodegradation process using Ag-doped TiO₂ nanostructures will be addressed. Two morphologies were introduced; nanoparticles and nanofibers. The nanofibers were synthesized by electrospinning of a sol–gel consisting of titanium isopropoxide, silver nitrate and poly(vinyl acetate). The silver nitrate amount was changed to produce nanofibers having different silver contents. The nanoparticles were prepared from the same sol-gels, however instead of spinning the gels were dried, grinded and sintered. The experimental and analytical studies indicate that doping by silver reveals to form anatase and rutile when the silver nitrate content in the mother solution was more than 3 wt%. The rutile phase content is directly proportional with the AgNO₃ concentration. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. In contrast to the known influence of the temperature on the chemical reactions, in case of the nanofibrous morphology of Ag-doped TiO₂, the temperature has negative impact on the photoactivity.