TiO 2 polycrystalline sub-micron fibers can be used as photocatalysts for the degradation of a variety of organic molecules. Here we report on the optimization of these fibers for decontaminating pharmaceutical agents in aqueous medical waste streams. Mixed-phase TiO 2 fibers have been prepared via a sol-gel technique followed by electrospinning and calcination. By adjusting the calcination temperature, the rutile phase fraction in TiO 2 fibers can be tuned relative to the anatase phase from 0% to 100%. The effect of rutile phase fraction on grain size and specific surface area as well as their subsequent influences on the photocatalytic activity was investigated. An optimal grain size in post-calcined TiO 2 fibers was found to be critical to balance the e-/h + volume recombination, surface recombination rate, and charge diffusion rate. The photocatalytic activities of the post-calcined TiO 2 fibers with different rutile fractions were measured by monitoring the decreasing concentration of phenazopyridine in aqueous solution under UV illumination using UV-Vis absorption spectroscopy. Post-calcined TiO 2 fibers composing of 38 wt% rutile and 62 wt% anatase exhibited the highest initial degradation rate constant of 0.044 min-1. This optimal photocatalytic activity can be attributed to the combined influences of the fibers' phase composition, surface area and grain size.

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The surface properties of TiO 2 nanofibers were utilized for the in-situ and ex-situ nucleation and growth of metal nanoparticles. Pt nanoparticles were generated on the titania surface without the use of external stabilizing agents. These nanoparticles were effectively anchored on the numerous pores present on the TiO 2 surface and acted as sites for continued nanoparticle growth. The TiO 2 surface exhibited extensive folding resulting in increased surface area that was then explored for the effective adsorption of reacting materials for heterogeneous catalysis. The resulting TiO 2-based catalysts were found to facilitate UV/Visible light sensitized degradation of Rhodamine B (RH-B). The photodegradation followed first order kinetics with a rate constant of 0.0158 min-1. An investigation of the mechanism of RH-B degradation suggests a role of reactive oxygen species (ROS) as intermediates in the photodegradation process.

The synthesis and application of environmentally benign, efficient and low cost heterogeneous catalysts is increasingly important for affordable and clean chemical technologies. Nanomaterials have been proposed to have new and exciting properties relative to their bulk counterparts due to the quantum level interactions that exist at nanoscale. These materials also offer enormous surface to volume ratios that would be invaluable in heterogeneous catalysis. Recent studies point at titanium dioxide nanomaterials as having strong potential to be applied in heterogeneous photocatalysis for environmental remediation and pollution control. This work reports the use of surface modified anatase TiO2 nanofibers with rhodium (Rh) nanoparticles in the photodegradation of rhodamine B (RH-B), an organic pollutant. The dimensions of TiO2 nanofibers were 150±50 nm in diameter and the size of the Rh nanoparticles was ~5 nm. The Rh-doped TiO2 catalyst exhibited an enhanced photocatalytic activity in photodegradation of rhodamine B under visible light irradiation, with 95 % degradation within 180 minutes reaction time. Undoped TiO2 did not show any notable phocatalytic activity under visible light.

Nanocomposites of gold nanoparticles (AuNPs) embedded in polyaniline fibers have been fabricated using a one-pot synthesis approach and in-situ polymerization. By using a combination of inorganic acids (e.g. HCl) and camphorsulfonic acid, polyaniline nanostructured fibers of high aspect ratio with diameters of 150 ± 50 nm and several micrometers in length were obtained. These fibers afforded high electrical conductivity of 4.2 ± 0.5 S/cm. Encapsulation of the AuNPs in the polyaniline fibers afforded nanocomposites with high electrical conductivity and dielectric constant of 34.0 ± 0.5 S/cm and 65.3 ± 5 respectively. The morphology of these materials was analyzed using SEM and HRTEM and electronic properties were analyzed using UV-Vis spectroscopy.