Novel Photocatalytic And Antibacterial Materials: Wet Chemistry Synthesis And Properties

The application of photo catalytic technology for pollution treatment has attracted a lot of attention in all countries.The preparation and application of the photocatalysts with high activity and effective under the sunlight have become hot topics in the areas of materials science,chemistry,environmental science and energy science.TiO₂ photocatalyst is widely regarded as a promising material for photocatalytic application due to its low cost,non-toxicity,chemically stability,high photocatalytic activity,and antibacterial property.However,TiO₂ is flawed from its wide bandgap and high recombination of photo-generated electrons and holes,which make it only effective under ultraviolet irradiation and decrease its photocatalytic efficiency.Therefore,it is meaningful to fabricate with high photocatalytic efficiency and synthesize photocatalysts effective under visible light irradiation.The synthesis and modification of TiO₂ nanotubes,mesoporous TiO₂,TiO₂ with multiple phases,and BiVO₄ were discussed in the present dissertation.And the antibacterial properties of Ag/TiO₂ composites were also discussed.Some new and interesting results were achieved and listed as follows.A chemical deposition-photoreduction approach was proposed to fabricate Ag/TiO₂-NTs composites with TiO₂-NTs prepared via a hydrothermal method as substrates.It was found that Ag nanoparticles with sizes of 3-5nm were highly and tightly dispersed on the surface of TiO₂-NTs when the content of Ag was 2.50 at.% and the concentration of NaOH solution was 0.30 mol·L^-1.Deposition of Ag could effectively enhance the photocatalytic efficiency of TiO₂-NTs.And the Ag/TiO₂-NTs composites with an Ag/Ti atomic ratio of 2.5 at.%showed the highest photocatalytic efficiency.Ag/TiO₂-NTs composites also showed excellent antibacterial performance to E.coli and S.aureus in the absence of UV irradiation.Ag is located on the surface of TiO₂-NTs in zero oxidation state.Schottky barrier is generated when Ag/TiO₂-NTs composites are irradiated under ultraviolet light.The recombination of electrons and holes is inhibited due to the existence of Schottky barrier,thus the improvement of the photocatalytic efficiency of TiO₂-NTs.Copper ions surface-doped TiO₂-NTS were prepared via a surface chemical reaction method.The effects of Cu doping concentration and calcination temperature on the crystal structure and morphology of the samples were investigated.TiO₂-NTs surface doped with a suitable amount of copper ions showed higher efficiency than the undoped TiO₂-NTs for photocatalysis of Rhodamine B.And the doped TiO₂-NTs with a Cu/Ti atomic ratio of 0.3 at.%showed the highest photocatalytic efficiency. Two kinds of copper species of Cu²⁺ and Cu⁺ were found on the surface of TiO₂-NTs. Cu²⁺ and Cu⁺ play roles as electron trappers facilitating the separation of photo-generated electrons and holes of TiO₂-NTs,improving the photocatalytic efficiency of TiO₂-NTs.The bandgap of TiO₂-NTs is narrowed due to the surface doping of copper ions,which enhances the absorption of TiO₂-NTs in the visible light zone.A simple ultrasonic-hydrothermal approach was proposed to fabricate Fe doped mesoporous TiO₂ microspheres with a combination of regular morphology,large specific surface area and high crystallinity.The effects of experimental parameters on the morphology and mesoporous structure of the samples were discussed.When the Fe doping concentration was 0.50 at.%,reaction temperature was 150℃,reaction time was 20h,and calcination temperature was 450℃,the sample possessed the largest specific surface area of 182.75m²Â·g^-1,an average pore diameter of 4.39nm,and a pore volume of 0.196cm³Â·g^-1.Fe³⁺ions act as electron and hole trappers facilitating the separation of photo-generated electrons and holes of TiO₂,improving the photocatalytic efficiency of the samples.The bandgap of mesoporous TiO₂ microspheres is narrowed due to the doping of Fe ions,which enhances the absorption of samples in the visible light zone.TiO₂ with multiple phases were prepared by hydrothermal methods.The effects of experimental parameters on the phase compositions and morphologies of the samples were discussed.Novel maple fruit-like,leaf-like,and flower-like TiO₂ nanoparticles were controlled synthesized.Multiple phased TiO₂ with a phase composition of 37.4%anatase,35.8%rutile,and 26.8%brookite showed the higher reaction rate constant for photodegradation of MO anatase TiO₂-NTs.Deposition of Ag could effectively enhance the photocatalytic efficiency of multiple phased TiO₂. And the Ag/multiple phased TiO₂ composites with an Ag/Ti atomic ratio of 2.0 at.% showed the highest photocatalytic efficiency.A simple hydrothermal method was proposed to prepare monoclinic BiVO₄ with regular morphologies.The effects of pH and surfactant on the crystal structure and morphologies of the samples were discussed.BiVO₄ nanorods,cuboids,cubic plates, and flower-like structures were obtained via tailoring the pH of reaction solution and using CTAB.A brief growth mechanism of the samples with various morphologies was proposed.The bandgap of the as-prepared monoclinic BiVO₄ is 2.40 eV.Those BiVO₄ showed much high efficiency for photodegradation of MO under the sunlight than TiO₂-NTs.