Optimizing Synthesis Of One Dimensional TiO₂ Nanoarrays And Their Photo Catalytic Properties

One-dimensional nanostructured titanium dioxide?TiO₂?arrays,as a very unique semiconductor structure,have shown great application values in the field of environment and energy,because of their high stability,low cost,excellent optical and electrical properties,environmental friendliness and perfect geometric characteristics.Therefore,it is a hot topic to optimize the preparation,surface modification and structure of the one-dimensional TiO₂ nanorods on the specific substrate for enhancing the photocatalytic and photoelectrochemical performance.In this paper,one-dimensional nanostructured TiO₂ arrays were prepared by hydrothermal method under acidic conditions.The in-situ transition of one-dimensional nanorods to nanotube arrays was realized.The effects of hydrothermal substrates,times and reactant concentrations on the structure and properties were studied.The obtained one-dimensional nanoarrays were modified by semiconductors and noble metals,and the composite structures was fabricated.The photocatalytic and photoelectrochemical performance of the TiO₂ nanoarrays nanostructures were improved.The application of the catalysts as environment-friendly catalysts was also discussed.The main contents are as follows:1.The effects of grown substrates?FTO and glass?on the morphologies of TiO₂ and the optical properties of products are investigated.TiO₂ grown on conductive side of FTO side exhibit highly ordered nanorods?NRs?in longitudinal direction and TiO₂ grown on glass side show scattered nanoflowers?NFs?morphology.The photocatalytic properties of the NRs and NFs were studied and the prepared TiO₂ NRs exhibited the highest photocatalytic efficiency?96.1%?due to their unique morphology and larger specific surface area.2.By simply stopping the reaction at certain times for different samples?e.g.,2.5,5,10,15 h?,we were able to obtain nanoarrays with distinct morphologies.The different surface morphologies include nanorods?2.5 h?,nanorods with small nanopariticles?5 h?,tree nuts?10 h?,and nanoflowers?15 h?.Creating this series of nanoarrays gives us "snapshots" of the growth process of the flower structured nanoarrays.The XRD and Raman spectra indicate that all TiO₂ hierarchical nanoarrays prepared in this work have a pure rutile structure.By analyzing the optical properties,over the series of nanoarrays formed from increasing reaction times,the average absorbencies first decreases from 0.821 to 0.646 and then increases to 0.870.The band gaps across the series also first decreases from 3.063 eV to 2.982 eV,and then increases to 3.015 eV.3.CdS nanoparticles-sensitized TiO₂ nanorods were prepared on FTO substrates using a successive ion layer adsorption and reaction method.The TiO₂ nanorods sensitized with CdS nanoparticles demonstrated enhanced visible-light absorption compared with the bare TiO₂ nanorods.They also exhibit enhanced photoelectrochemical and photocatalytic properties due to more efficient separation of photogenerated electrons.The TiO₂ nanorods sensitized with 8 SILAR cycles of CdS nanoparticles show the best properties,with a degradation rate?42.96%?of methyl orange and photocurrent density?168.5 ?A/cm2?under visible light that are enhanced by 92.4%and 70.3%compared to bare TiO₂ nanorods.4.TiO₂ nanorods were converted to nanotubes by hydrothermal selective etching treatment.Ag nanoparticles were further sensitized onto TiO₂ nanorods and nanotubes using a simple photodeposition approach.'The resulting Ag-TiO₂ nanotubes possessed a large specific area?116 M2g-1?and abundant mesoporous with Ag nanoparticles homogeneously dispersed on the surface of TiO₂ nanotubes.Photodegradation experiments showed that the Ag-TiO₂ nanotubes has a superior photocatalytic activity?98.8%?with respect to degradation of MO.The unique morphology and doping of Ag nanoparticles resulted in improved photocatalytic activity.5.TiO₂/ZnO/Ag heterojunction was successfully synthesized on FTO substrate trough a three-step method.The prepared TiO₂/ZnO/Ag nanostructures exhibited enhanced optical and photocatalytic properties than the bare TiO₂ and TiO₂/ZnO.The ZnO nanoparticles exhibited a synergistic effect,which increased the degradation of MO about 35%,compared to pure TiO₂ nanorods.When Ag QDs were put onto TiO₂/ZnO heterojunction by a photodeposition approach,the degradation of MO was increased by 35%,compared to TiO₂/ZnO heterojunction.The degradation of MO under UV-light irradiation with the TiO₂/ZnO/Ag nanostructures was relatively rapid,with completion in 30 min.Furthermore,the degradation capacity of TiO₂/ZnO/Ag nanostructures did not display any discernible decrease after four degradation cycles.The superior properties of the nanostructures could be ascribed to the unique structure of TiO₂/ZnO and the SPR effect of Ag QDs.Notably,the Ag QDs introduced into the semiconductor-semiconductor heterojunctions provide a new strategy for designing new photocatalysts for waste water treatment.