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TiO 2 is one of the wonder materials that possess extraordinary engineering versatility in terms of nanostructures, shapes and morphology. TiO 2 nanomaterials have shown superior antibacterial capability, it is however still unclear about the intrinsic dimensional effects on antibacterial mechanisms. This study reported a fundamental antibacterial mechanism about the intrinsic antibacterial capabilities of the engineered nanostructured TiO 2 materials (ENMs) – from three aspects 1) the structures of such nanoparticles, rods, tubes, fibres and spheres; 2) sizes/diameters/length of the ENMs; 3) combined effect due to dimensions and structures. Experimental results revealed that, the 1 D nanotubular TiO 2 , being the smallest individual ENMs possessed the highest toxicity towards E. coli; further studies showed that 3 D dendritic nanostructure incorporated with 1 D ultrathin TiO 2 nanorods had the highest antibacterial efficiency. Comparative studies have suggested that, the well-engineered 3 D TiO 2 nanomaterials (microspheres) with enhanced surface properties such as evenly grown 1 D sub-structures were more aggressive than the cluster aggregated 1D nanomaterials. In-depth research concluded that with well-controlled nanorods density and length, the integrated 3 D ENMs exhibited most efficient antibacterial activities. Such results could benefit the future antibacterial applications and the agent fabrications. [ABSTRACT FROM AUTHOR]

We report a facile non-hydrothermal method for the large-scale production of hierarchical TiO2 nanorod spheres for the photocatalytic elimination of contaminants and killing bacteria. Crescent Ti/RF spheres were prepared by deliberately adding titanium trichloride (TiCl3) to the reaction of resorcinol (R) and formaldehyde (F) in an open reactor under heating and stirring. The hierarchical TiO2 nanorod spheres were obtained by calcining the crescent Ti/RF spheres in a furnace in air to burn off the RF spheres. This method has many merits, such as large-scale production, good crystallisation of TiO2, and good reproducibility, all of which are difficult to realise by conventional hydrothermal methods. The calcination temperature plays a significant role in influencing the morphology, crystallisation, porosity, Brunauer-Emmett-Teller (BET) specific surface area, and hierarchy of the TiO2 nanorod spheres, thus resulting in different photocatalytic performances under UV light and solar light irradiation. The experimental results have demonstrated that the hierarchical TiO2 nanorod spheres obtained after calcination of the crescent Ti/RF spheres at different temperatures displayed similar photocatalytic activities under irradiation with UV light. We attribute this to a balance of opposing effects of the investigated factors. A higher calcination temperature leads to greater light absorption capability of the TiO2 nanorod spheres, thus resulting in higher photocatalytic antibacterial activity under solar light irradiation. It is also interesting to note that the hierarchical TiO2 nanorod spheres displayed intrinsic antibacterial activity in the absence of light irradiation, apparently because their sharp outward spikes can easily pierce and penetrate the walls of bacteria. In this study, the sharpest hierarchical TiO2 nanorod spheres were obtained after calcination at 500 °C, and these exhibited the highest antibacterial activity without light irradiation. A higher calcination temperature proved detrimental to the sharpness of the TiO2 nanorods, thus reducing their intrinsic antibacterial activity. [ABSTRACT FROM AUTHOR]

Inspired by the highly efficient hierarchical structure of plants that use natural light, the hierarchical 'forest-like' TiO2 nanofiber/ZnO nanorod/CuO nanoparticle ternary material 2 is synthesized by a stepwise process: electrospinning of TiO2 nanofibers, hydrothermal growth of ZnO nanorods, and photodeposition of CuO nanoparticles. Material 2 has a higher photodegradation rate of acid orange (AO 7) and stronger antibacterial capability under irradiation with solar light in comparison to that of the hierarchical 'tree-like' TiO2 nanofiber/ZnO nanorod material 1 and one dimensional as-spun TiO2 nanofibers. These enhancements result from the unique hierarchical forest- and tree-like features of materials 1 and 2, which enhance the light absorption capability, increase the specific surface area for mass transfer and bacteria attachment, create more reaction sites, and retard the recombination of photogenerated electrons and holes. A proportional relationship was found between the photocatalytic activity and the hierarchy of the materials. The sizes of the hierarchical nanostructured materials are in the micron range, which provides the opportunity for using these materials in engineering applications. [ABSTRACT FROM AUTHOR]

Abstract: To counter the global water crisis such as water resources scarcity and water quality deterioration, membrane filtration has been widely used as a promising technology. Recently, nano-materials and its structured membranes demonstrated multifunctional water purification capability in terms of decontamination and disinfection. Here, hierarchical nitrogen (N)-doped “nut-like” ZnO nanostructured material was hydrothermally synthesized at large scale. This hierarchical N-doped “nut-like” ZnO nanostructured material was well characterized and successfully assembled on a piece of polymer membrane surface to create a multifunctional membrane. This newly developed membrane demonstrated high pollutants removal ability via rejection and photodegradation, and strong antibacterial growth ability under visible light irradiation. At the same time, this novel membrane holds the potential to produce clean water at a constant high flux. The experimental results indicated that the hierarchical N-doped ZnO “nut-like” nanostructured material enhanced the photocatalytic activity in a comparison to commercial ZnO powder. This is caused by enlarging the specific surface area and enhancing the light utilization rate. It is reasonable to believe this hierarchical N-doped “nut-like” ZnO nanostructured membrane would benefit the water purification field. [Copyright &y& Elsevier]

Abstract: Here we present a simple two-phase assembling method to produce high-quality graphene oxide–TiO2 nanorod composites (GO–TiO2 NRCs) on gram scale. TiO2 nanorods dispersed in toluene are synthesized from a facile two-phase hydrothermal method. The effective attachment of TiO2 nanorods on the whole GO sheets at the water–toluene interface is confirmed by Transmission Electron Microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The as-synthesized TiO2 nanorods show a slightly higher efficiency in the photocatalytic degradation of C. I. Acid Orange 7 (AO 7) irradiated under UV light (λ =254nm) and higher antibacterial activity under simulated sunlight than that of TiO2 nanoparticles with the same diameter. After combined with graphene oxide (GO), the GO–TiO2 NRCs show much higher photocatalytic activities than that of TiO2 nanorods alone and the GO–TiO2 nanoparticle composites (GO–TiO2 NPCs). The ratio of TiO2 and GO has no evident effect on the photocatalytic activity of GO–TiO2 NRCs when all the TiO2 nanorods are anchored on the GO sheets. The higher photocatalytic activity of GO–TiO2 NRCs is ascribed to the anti-charge recombination and the more (101) facets. Considering the superior photocatalytic activity of GO–TiO2 NRCs and the fact that they can been easily mass-produced, we expect this material may find important applications in environmental engineering and other fields. [Copyright &y& Elsevier]