Oxygen Level Controlled\nPolymorphic Transformation\nin Sol–Gel Processed Electrospun TiO₂ Nanofibers

Abstract

The anatase phase of titania (TiO₂) is familiar\nfor\nits enhanced photocatalytic activities and smart window applications.\nIn this study, a crystallographic transformation route to achieve\nnanofibers of anatase TiO₂ nanocrystals has been developed\nthrough an environmentally controlled sol–gel and electrospinning\nmethods. Two types of TiO₂ nanofibers were synthesized\nusing two different sols prepared under 105 and 315 ppm of the O₂ environment within an Ar glovebox using titanium isopropoxide\nprecursor and heat-treated at 500 °C for 5 h. The nanofibers\nwere characterized using scanning electron microscopy (SEM), energy\ndispersive X-ray (EDX), X-ray diffraction (XRD), and transmission\nelectron microscopy (TEM) methods. Both of XRD and TEM analysis confirmed\nthat the nanofibers processed from low O₂ condition are\nanatase. In contrast, mixtures of anatase and rutile phase nanofibers\nwere obtained whose sol was processed under higher O₂ condition.\nAs the nanofibers have a higher surface area-to-volume ratio, they\nwould significantly contribute to enhancing the photocatalytic activities\nof TiO₂.