Synthesis, Self-assembly And Properties Of Semiconductor Hollow Nanospheres

Semiconductor hollow nanospheres have attracted great attention in recent years. Semiconductors are well known for their optical, electrical and magnetic properties. Excellent properties can be achieved through designing the morphology and species of the hollow nanospheres. In this study, we focused on preparation of semiconductor hollow nanospheres such as PS/ZnS, PS/Au/CdS and investigated properties of the corresponding nanofilms.(1) In the first chapter, we present a simple and effective strategy to construct a UV photodetector based on ZnS hollow-spheres by oil-water interfacial assembly of polystyrene (PS)/ZnS colloidal nanospheres followed by annealing treatment. In this approach, PS/ZnS colloidal nanospheres were prepared and then self-assembled into a closely-packed PS/ZnS nanofilm at a "hexane-water" interface. By annealing this precursor nanofilm under an optimal condition, a ZnS hollow-sphere nanofilm with a densely-packed network structure was obtained. The particle size and morphology of the PS/ZnS colloidal nanospheres and the as-transformed ZnS hollow spheres were characterized with TEM, HRTEM and SEM. Finally, a UV photodetector was successfully constructed from the as-transformed ZnS hollow-sphere nanofilm. Moreover, the photocurrent is nearly30times greater than a single-crystalline ZnS nanobelt based UV photodetector presented in recent literature. Besides, the as-prepared photodetecor has low dark current and good repeatability, which makes it suitable for application in photodetection field.(2) In the second chapter, we present the first successful fabrication of well-ordered bilayer nanofilm-based photodetectors consisting of abundant wurtzite ZnS and ZnO hollow nanospheres using the oil-water interfacial self-assembly technology. Their photo-responsive behavior was found to depend considerably on the stacking orders of the hollow microspheres in the multilayer films. The optimal performance of these bilayer nanofilm-based photodetectors was significantly enhanced compared with that of monolayer-nanofilm based devices reported in previous works. Its photocurrent is comparable with that of commercial GaN-based UV photodetectors, which implicates its potential application in commercial field. (3) In the third chapter, we present a simple method to prepare PS/Au/CdS composite nanospheres. In this approach, HAuCl4which was used as precursor was transformed to Au nanoparticles without adding any reducing agent. The number of loaded Au particles can be tailored by the concentration of its precursor. PS/Au/CdS composite nanospheres and its corresponding nanofilms were then prepared with Cd(Ac)2and TAA via oil-water interfacial self-assembly technology. The PEC performance is tested and discussed. The CdS-Au sample is more photoactive as compare to the pure CdS sample. The photocurrent increases up to220μA at0.5V. Besides, the electrode was proved to have good stability and fast respond speed.