Synthesis of TiO2 nanocrystals controlled by means of the size of magnetic elements and the level of doping with them
Synthesis of TiO2 nanocrystals controlled by means of the size of magnetic elements and the level of doping with them
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DOI：
10.1088/0953-8984/21/6/064214
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发表时间：
2009-02
期刊：
影响因子：
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通讯作者：
H. Nakano;N. Hasuike;K. Kisoda;Koji Nishio;T. Isshiki;H. Harima
中科院分区：
文献类型：
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作者：
H. Nakano;N. Hasuike;K. Kisoda;Koji Nishio;T. Isshiki;H. Harima
采用水解结合热处理的方法合成了TiO 2纳米晶。通过控制前驱体溶液的pH值，选择性地合成了具有金红石和金红石结构的TiO 2纳米晶，并通过改变反应温度来控制晶粒尺寸。此外，通过向前驱体溶液中添加Co，还合成了具有金红石结构的Co掺杂TiO 2纳米晶。在测试的样品中不存在诸如Co沉淀物和Co氧化物的第二相，其中[Co]<10摩尔%。随着Co掺杂水平的增加，447 cm-1处的Eg-phonon信号变宽并向较低频率偏移，表明Co掺入金红石TiO 2主晶格和晶格膨胀。光吸收光谱表明，Co掺杂后，TiO 2的吸收边在3.0 eV处对应于金红石型TiO 2的带隙，并向低能侧移动。这些结果表明，通过Co掺杂的金红石型TiO 2的带隙工程的可能性。另一方面，O 2 p和Co 3d轨道之间的电荷转移间隙也观察到与Co的样品，这表明在金红石型TiO 2纳米晶，通过可见光照射获得的光致磁性的可能性。
TiO2 nanocrystals were synthesized by a hydrolysis method combined with a thermal treatment. TiO2 nanocrystals with rutile and anatase structure were selectively synthesized by controlling the pH level in the precursor solution, and the crystallite size was controlled by changing the reaction temperature. Moreover, Co-doped TiO2 nanocrystals with rutile structure were also synthesized by means of the addition of Co to the precursor solution. Secondary phases such as Co precipitates and Co oxide were not present in the sample tested, with [Co]<10 mol%. With an increase in the Co doping level, the Eg-phonon signal at 447 cm−1 was broadened and shifted to a lower frequency, indicating the incorporation of Co into the rutile TiO2 host lattice and lattice expansion. Optical absorption spectra showed that the absorption edge at ∼3.0 eV corresponded to the band gap of rutile TiO2 and shifted to the lower energy side upon Co doping. These results indicated the possibility of band gap engineering of rutile TiO2 via Co doping. On the other hand, the charge transfer gap between O 2p and Co 3d orbitals was also observed for samples with Co, suggesting the possibility of photo-induced magnetism in rutile TiO2 nanocrystals, obtained by visible light irradiation.