【作者】 张小俊；

【导师】 ??；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2007， 博士

【摘要】 介孔材料由于具有很高的比表面和孔洞率，孔壁上存在大量的不饱和键或悬空键而具有很高的活性，纳米微粒的表面活性也很高，且具有很多不同于块体材料的特性。将纳米颗粒组装到介孔固体中形成的介孔复合体，不但使纳米微粒的许多特性得到充分的发挥，而且由于孔壁和纳米微粒之间的相互作用，使复合体极易产生一些分散纳米微粒和介孔固体本身所不具备的物性。因此探索一种操作性强，对分散纳米粒子易于控制的制备方法对介孔复合体乃至纳米粒子的物性的全面考察都有着重要的意义。有鉴于此，本文主要做了以下几方面的工作：1．将sol-gel过程和γ-射线辐照相结合发展了一种制备介孔复合体的新方法，成功合成了纳米Cu／SiO₂及Cu₂O／SiO₂介孔复合体，并用XRD，电镜（TEM），XPS和紫外-可见光吸收测量等对复合体进行了表征，揭示了SiO₂基质对介孔中Cu微粒光学性质的影响，并将处理金属微粒光学性质的经典理论与量子效应相结合并借助于X-射线光电子能谱（XPS）对Cu／SiO₂介孔复合体的光学性质进行了分析和讨论，说明了材料的光学性质是Cu纳米粒子内在的量子尺寸效应和外在基质的影响（通过界面相互作用）共同调制的结果。2．考虑到基底和金属粒子之间的影响，将具有很好光学性质的TiO₂引入到SiO₂基底中，制备了SiO₂-TiO₂复合薄膜，然后利用Gamma辐照和水热还原的方法制备了不同的Cu／SiO₂-TiO₂介孔复合体，并且利用XRD，TEM，UV等对制备的介孔复合体进行了表征，结果证明，利用辐照方法制备的Cu／SiO₂-TiO₂介孔复合体中铜的粒径更小，分散性更好，也更均匀。在对其光学性质进行研究后，证明不但基质对金属粒子的光学性质有影响，且金属粒子对基质的光学性质也有影响。3．通过两步溶胶凝胶法成功制备了TiO₂／SiO₂介孔复合物，并且研究了在不同热处理温度下对甲基红的光降解作用。随着处理温度的升高，催化性能先升高后由小幅的下降。与相同条件下制备的TiO₂粉体的催化性能相比，在低温处理后，TiO₂／SiO₂介孔复合物的催化性能略小于TiO₂粉体，但在高温处理后，TiO₂／SiO₂介孔复合物的催化性能要远远的大于TiO₂粉体。因此，我们认为两步溶胶凝胶法制备的TiO₂／SiO₂介孔复合物可能在高温条件下具有良好的催化性能。4．利用抗坏血酸作为配位剂和还原剂，在表面活性剂PVP的辅助下，使用柠檬酸三钠作为助发泡剂，制备出了具有多孔结构的四方柱状结构的铜纳米棒，此种铜纳米棒具有较大的比表面，可望在金属催化性能上得到展示。5．利用草酸作为沉淀剂，成功的制备了10-100nmCuO纳米颗粒，并研究了其电化学性质。第一次放电的时候粒子越小，比表面越大，放电容量就越高；而第二次放电过程中，粒子越小，放电容量就越低。而通过XRD和SEM对放电后样品的研究证实，CuO颗粒基本都转变为Cu颗粒，且得到的Cu颗粒的粒径和制备出的CuO颗粒的粒径基本一致，因此，我们认为利用电化学方法，通过制备不同粒径的CuO纳米颗粒作为正极材料可以用来制备不同粒径的Cu纳米颗粒。更多还原

【Abstract】 Mesoporous solids possess high surface energy and chemical activity, because of the high specific surface area, great porosity rate and a large number of unsaturated bonds existing on their pore walls. Nanoparticles also hold high activity attributed to the size dependent properties and quantum size effect. Mesoporous nanocomposites prepared by nanoparticles incorporated into the pores of the mesoporous solids, not only retain the excellent properties of the dispersed nanoparticles sufficiently, but also will exhibit many new peculiarities resulting from the interactions of the particles and the matrix, which didn’t appear as either of them existed lonely. So it is significative to find an operable and easy sample nanoparticles preparation method in investigating the physical properties of the nanoparticles as well as the mesoporous composites. Based on the above, the work from five aspects below has been processed:1. The sol-gel process and theγ-ray irradiation were combined together to develop a new preparation method of mesoporous nanocomposite. We have successfully prepared the mesoporous SiO₂ composites with the small Cu₂O, Cu particles or clusters dispersed in the pores and were examined by x-ray diffraction （XRD）, transmission electron microscope （TEM）, x-ray photoelectron spectroscopy （XPS）, and the optical absorption spectroscopy. The optical absorption of the Cu/SiO₂ mesoporous composite revealed the matrix’s effect on the optical properties of the dispersed particles. The optical properties of the nanocomposites were analysed and discussed by combining the classical eletrodynamic theory and the quantum effects, and XPS were used to investigate the interaction between the Cu particles, and finally concluded that the optical properties of the CU/SiO₂ composite are collectively decided by the quantum size effect （QSE） and the effect from the matrix （through the interface interactions）.2. Based on the effect of the matrix on the nanoparticles, we introduced the TiO₂ that owns good optical properties to the SiO₂ matrix, and prepared the SiO₂-TiO₂ composite matrix. And then, we have successfully prepared various mesoporous SiO₂-TiO₂ composites with the Cu particles or clusters dispersed in the pores by theγ-ray irradiation and reductive methods. The structures of these composites were examined by x-ray diffraction （XRD）, transmission electron microscope （TEM）, x-ray photoelectron spectroscopy （XPS）, and the optical absorption spectroscopy. The particles prepared byγ-ray irradiation are smaller, more dispersive and more symmetrical than those prepared by reductive methods. And the study of the optical properties told us not only the matrix made an effect on the optical character of the metal nanoparticles, but also metal nanoparticles made an effect on the optical character of the matrix.3. TiO₂/SiO₂ composite were synthesized successfully by two step sol-gel method and its effect on the optical degradation of methyl red under heat treatment at different temperatures was studied. With the temperature of heat treatment increasing, the catalytic capability improved at first and then decreased a little. Compared with the catalytic capability of TiO₂ powder prepared under the same conditions, the catalytic capability of TiO₂/SiO₂ composite with low temperature treatment is a little less than that of TiO₂ powder, but after the high temperature treatment, the catalytic capability of TiO₂/SiO₂ composite is much more than that of TiO₂ powder. So we think that two step sol-gel preparation of TiO₂/SiO₂ composite may have excellent catalytic capability under high temperature.4. With the existence of the PVP as surfactant, porous copper nanorods with rectangular cross sections of column shape have been successfully prepared with the ascorbic acid as ligand and reducer, and the trisodium citrate as the assistant vesicant. The resultant porous copper nanorods may provide interesting possibilities for further applications in catalyzing for the large surface area.5. Well-dispersed cupric oxide （CuO） nanoparticles with the size from 10 nm to 100 nm were successfully synthesized by thermal decomposition of CuC₂O₄ precursor. The electrochemical tests showed an interesting phenomenon that the larger average size and the smaller surface of the particles are, the smaller discharge capacity of the first time is, while that of the second time is larger. However, by the study of the discharged sample with the XRD and SEM, almost all the CuO particles have changed as Cu particles. So, we believe that electrochemical method can synthesize Cu particles with different sizes by using the CuO particles with different sizes as the positive electrode.更多还原