| In recent years, monodisperse hollow structure materials have attracted much attention due to their unique properties such as low density and high specific surface area. They are widely used in many fields such as catalysis, drug controlled release, micro reactor, lithium ion batteries and so on. The synthetic strategies for hollow structures are broadly categorized into:traditional hard template method, sacrifice template method, soft template method, and free-template method. The most effective strategy is hard template method, which requires no additional surface functionalization and chemical reaction or calcinations to remove templates, so sacrifice template method is most promising. But in general, the hard template method has several intrinsic flaws:first, multistep synthesis process is difficult to achieve high yield; second, the shell may get to collapse or deformation after remove templates. Soft template method is easy template removal and efficient encapsulation of therapeutic and bioactive molecules. However, soft templates are usually thermodynamically unstable and can be influenced by factors such as the solution polarity, pH value and ionic strength of the solution; it is difficult to obtain monodisperse spherical structure. Template-free strategies can overcome the demerits of template strategies. However, this strategies also have their own limitations, such as the ostwald ripening is only suitable for the synthesis of hollow spheres from certain metal oxide structure. So, there’s a challenge need to explore new method of assembly hollow materials, especially the preparation of unique optical/electrical properties of semiconductor materials and hybrid semiconductor materials.PMAA polymer microsphere by distillation precipitation polymerization method to synthesis with a narrow size, excellent monodispersity, and carboxyl surface, so as to satisfy the inside conditions as a sacrifice template, can contribute to surface adsorption of metal precursor and surface deposition of nanoparticles. Based on the polymer microspheres with uniform size we have done the following research:(1) We synthesized hollow ZnS microspheres through a facile and efficient one-pot DMF solvent heat method and use the PMAA polymer microsphere as self-sacrifice template. Tuning of the cavity diameter, the shell thickness and the size of the crystal shape of ZnS microspheres can be achieved by changing the molar ratio of Zinc (Ⅱ) acetylacetonate with thioacetamide (TAA) and the heating time. The resultant semiconductor nano-materials were characterized by means of different techniques including transmission electron microscopy (TEM) indicate that these materials exhibit stable high surface area nanoporous frameworks with well-defined external morphology, X-ray diffraction(XRD), TGA, FT-IR studied the sacrifice of the template removal mechanism and the formation process of the hollow shell, and through UV-vis, PL, XPS, ASAP experiments and other testing method analyzes the physical properties of materials. The photocatalytic activity of the as-prepared hollow microspheres was tested by degrading dyes methyl orange, the results show that hollow microspheres with higher photocatalytic activity than commercial ZnS.(2) In order to study the commonality of PMAA polymer microsphere as sacrifice template, we integrated PMAA with sodium acetate to form PMAANa salt and dispersed in ethanol, then cation exchange with various metal nitrates, such as In2+, Cu2+, Fe3+, Zn2+, Mn2+, Sn2+, Co2+, etc., and form PMAAM salt precursor polymer microspheres.Then we get a series of different multilevel hollow structure of metal oxide nanomaterials, such as Fe2O3, InO, CuO, MnO, SnO2, Co3O4, etc., by precise control of heating rate and calcination to remove the PMAA microspheres core. In the other hand, we try to spread PMAAM precursor in the tertiary butyl alcohol solution and control spin-coating speed, and then calcined PMAA core to expect to get a good3D hollow metal oxide film. The resultants characterized by TEM, SEM, XRD, TGA experiment.This method is facil and using cation exchange with metal nitrate as the precursor, making this method is simple, general and suitable for mass synthesising most of the metal oxide hollow structure or hybrid hollow metal oxide. |
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