Formation and characterization of self-organized TiO2 nanotube arrays by pulse anodization.
Formation and characterization of self-organized TiO2 nanotube arrays by pulse anodization.
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DOI：
10.1021/ja076092a
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发表时间：
2008-01
影响因子：
15
通讯作者：
W. Chanmanee;A. Watcharenwong;C. R. Chenthamarakshan;P. Kajitvichyanukul;N. R. de Tacconi;K. Rajeshwar
中科院分区：
文献类型：
--
作者：
W. Chanmanee;A. Watcharenwong;C. R. Chenthamarakshan;P. Kajitvichyanukul;N. R. de Tacconi;K. Rajeshwar
本文描述了利用脉冲电压波形对钛衬底进行阳极氧化制备的二氧化钛纳米管阵列。在脉冲波形的下限，脉冲电压在20~-4V或20~0V之间，持续时间从2到16 S。在本实验中，使用氟化铵或氟化钠(及其混合物)作为电解液，添加或不添加介质改性剂(甘油、乙二醇或聚乙二醇(PEG400))。对脉冲波形进行了优化，以在阴极电流流区内电化学生长纳米管并对其管壁进行化学刻蚀。与传统的连续阳极氧化法生长的样品相比，所得到的纳米管阵列显示出更高质量的纳米管阵列形态和光响应。与其他脉冲宽度相比，在20V/-4V脉冲序列和负电压下脉宽为2 S的情况下生长的薄膜具有更好的光响应性能。具体地说，脉冲的负电压限制(-4V)及其持续时间促进了NH4+物种的吸附，进而抑制了电解液F-物种对生长的氧化物纳米结构的化学侵蚀。负电压下的脉冲周期越长，纳米管壁越厚，长度越短。不同的是，在0V的低电压下，脉冲宽度越长，氧化物纳米管壁越薄，这表明氟离子的化学侵蚀不会被NH3/NH4+物种的吸附所抵消，这与-4V时的界面情况不同。最后，本研究结果为支持现有的氧化物纳米管阵列在母材表面的阳极生长和自组装的机理模型提供了有用的证据。
This paper describes TiO2 nanotube arrays prepared by anodic oxidation of Ti substrates using pulse voltage waveforms. Voltages were pulsed between 20 and -4 V or between 20 and 0 V with varying durations from 2 to 16 s at the lower limit of the pulse waveform. Ammonium fluoride or sodium fluoride (and mixtures of both) was used as the electrolyte with or without added medium modifier (glycerol, ethylene glycol, or poly (ethylene glycol) (PEG 400)) in these experiments. The pulse waveform was optimized to electrochemically grow TiO2 nanotubes and chemically etch their walls during its cathodic current flow regime. The resultant TiO2 nanotube arrays showed a higher quality of nanotube array morphology and photoresponse than samples grown via the conventional continuous anodization method. Films grown with a 20 V/-4 V pulse sequence and pulse duration of 2 s at its negative voltage limit afforded a superior photoresponse compared to other pulse durations. Specifically, the negative voltage limit of the pulse (-4 V) and its duration promote the adsorption of NH4+ species that in turn inhibits chemical attack of the growing oxide nanoarchitecture by the electrolyte F- species. The longer the period of the pulse at the negative voltage limit, the thicker the nanotube walls and the shorter the nanotube length. At variance, with 0 V as the low voltage limit, the longer the pulse duration, the thinner the oxide nanotube wall, suggesting that chemical attack by fluoride ions is not counterbalanced by NH3/NH4+ species adsorption, unlike the interfacial situation prevailing at -4 V. Finally, the results from this study provide useful evidence in support of existing mechanistic models for anodic growth and self-assembly of oxide nanotube arrays on the parent metal surface.