Han Qiao-Feng, Chen Liang, Qiang Fei, Zhu Wen-Chao, Xu Bing, Wang Xin
Key Laboratory of Soft Chemistry and Function Material, Ministry of Education, Nanjing University of Science and Technology, Nanjing 210094, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 Nov;29(11):3011-4.
Ceria (CeO2) nanoparticles were prepared by precipitation method using cerium nitrate (Ce(NO3)3 x 6H2O) and ammonia (25 Wt%) as raw materials under the reaction for 3 h and ageing for 9 h at 80 degrees C without any surfactants and further calcination. The powder X-ray diffraction (XRD) pattern shows the as-prepared CeO2 crystals belong to the cubic phase and are well crystallized. Transmission electron microscopic (TEM) studies reveal that the appearance of as-prepared CeO2 is hexagonal, which is proposed to be the projection of polyhedral shape. The regular fringes spacing of 0.31 nm is in agreement with the d value of (111) lattice planes of cubic phase CeO2 from high-magnification TEM image. Reaction conditions such as the concentration of precipitant, reaction temperature and ageing duration exert important influence on the purity and morphology of the product. Ce(OH)3 was detected when the reaction was processed at lower pH (< 9) or with ageing duration less than 8 h at 80 degrees C. The size of polyhedral ceria nanoparticles increased with longer ageing time (> 15 h). If the reaction went on at a temperature lower than 40 degrees C, a large quantity of rodlike Ce(OH)3 was produced according to TEM observation. Raman spectra of CeO2 nanocrystallines exhibit a Raman shift at 465 cm(-1), corresponding to a F2g Raman band from the space group Fm3m of a cubic fluorite structure, while the Raman shift at about 600 cm(-1) may be attributed to the second Raman vibration mode of O2- vacancy due to Ce3+ impurity. Photoluminescence spectrum of CeO2 shows an emission at 465 nm at room temperature, which may be explained by charge transition from the 4f band to the valence band of CeO2.
以硝酸铈（Ce(NO₃)₃·6H₂O）和氨水（25 wt%）为原料，采用沉淀法制备二氧化铈（CeO₂）纳米颗粒。在无任何表面活性剂的情况下，于80℃反应3小时并老化9小时，然后进行进一步煅烧。粉末X射线衍射（XRD）图谱表明，所制备的CeO₂晶体属于立方相且结晶良好。透射电子显微镜（TEM）研究显示，所制备的CeO₂外观为六边形，推测这是多面体形状的投影。高倍TEM图像中0.31 nm的规则条纹间距与立方相CeO₂（111）晶格平面的d值一致。沉淀剂浓度、反应温度和老化时间等反应条件对产物的纯度和形态有重要影响。当反应在较低pH值（<9）下进行或在80℃老化时间少于8小时时，检测到Ce(OH)₃。多面体二氧化铈纳米颗粒的尺寸随老化时间延长（>15小时）而增大。如果反应在低于40℃的温度下进行，根据TEM观察会生成大量棒状Ce(OH)₃。CeO₂纳米晶体的拉曼光谱在465 cm⁻¹处出现拉曼位移，对应于立方萤石结构空间群Fm3m的F2g拉曼带，而约600 cm⁻¹处的拉曼位移可能归因于Ce³⁺杂质导致的O²⁻空位的第二拉曼振动模式。CeO₂的光致发光光谱在室温下于465 nm处有发射，这可能是由从CeO₂的4f带向价带的电荷转移来解释。
