Structural and optical properties of electrospun TiO2 nanofibers

The anatase TiO2 nanofibers of average diameters 60, 100, and 150 nm were fabricated by controlled electrospinning of a polymeric solution and subsequent sintering of the as-spun fibers. The sintered fibers were polycrystalline and composed of densely packed TiO2 grains of size similar to 12 nm. The rutile phase nucleated at the particle interface of the dense anatase TiO2 nanofibers at a temperature of <570 degrees C because of the increased surface stress observed in these nanotibers. X-ray and electron diffraction measurements and analysis of the sintered fibers showed that the lattice strain increased with a decrease in the fiber diameter. The diameter-dependent lattice strain is attributed to the increased surface energy in fibers of lower diameter. The strain most likely originates from interplay of the surface charge and grain boundary effects. The absorption spectra of the fibers showed a red shift with an increase in the fiber diameter, which is attributed to an increase in the surface stress with a decrease in the fiber diameter.