| The photocatalysis has attracted great interest for its low energy consumption and innocuity. Due to their unique physical and chemical properties, ZnO and Cu2O, as the new type multifunction inorganic materials, have wide application in treatment of environment pollution which is closely correlated with the survival and health of human beings. Therefore, the synthesis, modification and photocatalytic performance of ZnO and Gu2O have received tremendous attention. In this paper, the transition metal oxide photocatalysts (Cu2O and ZnO) were prepared and their photocatalytic performances were investigated in detail. This work mainly includes the following aspects:1. Preparation and characterization of Cu and Cu2O quantum dotsCu2O quantum dots were prepared by one-step chemical precipitation method using KBH4 as reductant. The obtained samples were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD). The results indicated that the sizes of Cu2O quantum dots could be tuned by varying the dosage of oleic acid and PVP. When 0.5 mL oleic acid and 0.5 g PVP were added, the as-prepared Cu2O quantum dots were uniform, and the average diameter was 2.2 nm. On the other hand, Cu quantum dots were prepared via hydrothermal method using oleic acid and oleylamine as the surfactant and reductant, respectively. The phase composition and size were characterized by XRD, TEM and high-resolution TEM (HRTEM). The influence of various synthetic parameters on the structure and phase composition of Cu quantum dots was systematically investigated, such as reaction temperature, reaction time, the dosage of oleic acid, oleylamine and water, respectively. The results showed that the dosage of water was the main factor that affected the formation of quantum dots. Oleic acid surves as the surfactants, and oleylamine acts both as the surfactant and the reducing agent.2. Self-assembly of Cu2O quantum dots and their photocatalytic performanceCu2O nanoparticles were prepared by self-assembly of Cu2O quantum dots with different morphology by using Cu2O quantum dots as basic building blocks. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), inductive coupled plasma emission spectrometer (ICP), respectively. The influence of different solvents and the dosage of diethyl carbonate for the morphology of self-assembly Cu2O were investigated in detail. The results indicated that the dosage of diethyl carbonate was the main factor for the morphology of self-assembly Cu2O, the kinds of solvents were the secondary factor. Secondly, Cu2O quantum dots was assembled into colloidal spheres by emulsion-based bottom-up self-assembly(EBS) strategy. Then the noble metal Au was deposited on the surface of colloidal spheres. The photocatalytic performance was investigated by photocatalytic degradation of methyl orange under UV-light irradiation. The results indicated that Cu2O-Au nanocomposites exhibited higher photocatalytic performance in comparison with pure Cu2O. Notably, when the content of Au was 0.61%, the photocatalytic degradation efficiency could reach 90%. Furthermore, the band gap was investigated by the UV-vis diffuse reflectance spectrum, and the separation efficiency of the electron-hole pairs was detected by fluorescence spectra. The results showed that the dopping of Au could reduce the band gap and increase the separation efficiency of the electron-hole pairs.3. Preparation and photocatalytic performance of ZnO and ZnO-Au25 colloidal spheresUsing zinc acetate as raw materials, ZnO colloidal spheres were synthesized in the presence of oleylamine, diethylene glycol and KOH solution at 120 ℃. It is obvious that the as-obtained ZnO nanospheres are uniform with an average diameter of ca.50 nm. Then, ZnO-Au25 nanocomposites were synthesized by doping Au25 nanoclusters into the porous ZnO nanospheres. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), inductive coupled plasma emission spectrometer (ICP), EDS-mapping and UV-vis absorption spectroscopy, respectively. The photocatalytic performance was investigated by photocatalytic degradation of rhodamine B under UV-light irradiation. The results indicated that, compared to pure ZnO and ZnO-Au nanoparticles, ZnO-Au25 colloidal spheres exhibited more higher photocatalytic activity. When the content of Au25 was 1.16%, the photocatalytic degradation efficiency could reach 99.8%. Furthermore, the band gap was investigated by the UV-vis diffuse reflectance spectrum, and the separation efficiency of the electron-hole pairs was detected by fluorescence spectrum. The results showed that the dopant of Au25 could reduce the band gap and increase the separation efficiency of electron-hole pairs. |
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