| Methylene blue(MB)has strong biological toxicity and can even cause diseases such as cancer.With the development of industrial process,only biodegradation method is not enough to solve the issue of environmental pollution caused by MB wastewater discharge,so it is particularly important to develop new treatment technology for dye wastewater.Photocatalytic technology is one of the environmentally friendly,economical and efficient pollutant treatment technologies proposed in recent decades.It has been widely used in many fields,e.g.dye degradation,air purification,preparation of hydrogen and oxygen,carbon dioxide reduction and etc.The most important thing of photocatalytic technology is to prepare efficient photocatalyst.Polyoxometalates have been considered as an excellent photocatalyst and have been widely used in the field of pollutant treatment,among which phosphotungstic acid(H3PW12O40,POM)has attracted wide attention because of its unique electronic properties and stability.However,POM itself cannot absorb visible light due to its wide energy band.To improve the photocatalytic efficiency,the preparation of hybrid materials consisting of POM and organic compounds has attracted much attention from researchers.In view of this,organic-inorganic hybrid materials based on POM were fabricated in this dissertation and applied to degradation of MB.The specific contents of the dessertation include three parts as follows.In chapter 1,some relevant background information was introduced and the research status at domestic and overseas of organic-inorganic hybrid materials based on polyoxometalates and degradation of dye molecules by photocatalytic technology in recent years were summarized.On this basis,the purpose of this dissertation was proposed.In chapter 2,based on ionic self-assembly strategy,organic-inorganic hybrid materials(POM-IL(Ci2))were prepared by the combination of POM with carboxyl functionalized surface active ionic liquid N-dodecyl-N’-carboxymethyl imidazolium bromide([N-C12,N’-COON-Im]Br,abbreviated as "IL(C12)" for convenience).TEM and SEM techniques were used to observe the morphologic evolution over time for the hybrids materials from nanoparticles to nanofibers.The results of mechanism investigation show that the main driving force of the morphologic evolution were hydrogen bond and hydrophobic interaction.We also obtained nano fibers by the living self-assembly method.It is found that this strategy can significantly reduce the energy barrier during the process of morphologic evolution,resulting in the time to form nanofibers from 7 d to 24 h.In addition,we also studied the photodegradation performance of POM-IL(C12)hybrid materials to MB under sunlight.In chapter 3,organic-inorganic hybrid nano fibers with excellent charge transfer properties were prepared by the strategy of bottom-up hierarchical self-assembly.Firstly,POM and IL(C12)were used to construct POM-IL(C12)nanoparticles.Then,the perylene imide(PDI)molecule with strong ability to absorb visible light and the POM-IL(C12)supermolecule were assembled to form PDI/POM-IL(C12)nanofibers by means of the rapid solution dispersion method.The morphology and structure of the hybrid materials were characterized by TEM,SEM,SAXS and XRD,respectively.The results of EDS showed that PDI and POM-IL(C12)were successfully assembled together.The results of fluorescence spectra,fluorescence lifetime and quantum yield show that the hybrid materials have strong charge transfer performance.In addition,DRS spectra showed that the absorption band edge of PDI/POM-IL(C12)hybrid materials was wider than that of single component,which helped to reduce the band gap energy.Finally,the photodegradation performance of the hybrid materials was evaluated by MB,and the possible photodegradation mechanism was speculated by Gaussian calculation.The PDI/POM-IL(C12)hybrid materials fabricated in this chapter has a good application prospect in the field of dye wasterwater treatment. |
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