稀碱溶液中水热法制备柔性TiO2纳米须薄膜的生长机制及表征

以柔性不锈钢基底上经磁控溅射沉积的钛膜为钛源, 在1 mol·L^-1的低浓度NaOH溶液中水热法制备了朝基底上方取向生长的大长径比柔性TiO₂纳米须薄膜, 考察了钛膜沉积条件对纳米须薄膜的影响, 系统研究了水热反应条件对薄膜生长过程的影响及TiO₂纳米须薄膜的形成机制. 通过场发射扫描电镜(FESEM)、X射线能谱仪(EDS)、高分辨透射电子显微镜(HRTEM)、X射线衍射仪(XRD)等对样品进行了表征. 结果表明, 与室温沉积的钛膜相比, 600 ℃下沉积的钛膜水热后得到的纳米线薄膜与基底的附着力更好. 所得TiO₂纳米须为单晶锐钛矿, 经由Na₂Ti₂O₄(OH)₂、H₂Ti₂O₅·H₂O转变而来. 纳米须形成于水热阶段, 平行于Na₂Ti₂O₄(OH)₂的(100)晶面择优取向生长, 纳米须经历了纳米片→纳米线束→纳米线的裂解生长过程. 朝基底上方取向生长的纳米须薄膜的形成是低浓度NaOH溶液与较高水热温度(220 ℃)协同作用的结果. 进一步在Na₂SO₄溶液中研究了薄膜电极的光电化学性能, 结果表明, TiO₂纳米须薄膜的光电性能明显优于零维纳米颗粒薄膜和二维纳米片薄膜, 显示了良好的应用前景.

Growth Mechanism and Characterization of Flexible TiO2 Nanowhisker Films Hydrothermally Synthesized in Dilute Alkaline Solution

Flexible oriented TiO₂ nanowhisker films with large aspect ratios were hydrothermally prepared in 1 mol·L^-1 NaOH solution from Ti film deposited by magnetron sputtering on a flexible stainless steel substrate. The influence of the Ti film deposition conditions on the resulting TiO₂ nanowhisker films was investigated. We also systematically studied the effects of the hydrothermal parameters on the nanowhisker films and their growth mechanism. The samples were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and high resolution transmission electron microscopy (HRTEM). The results showed that nanowhisker film prepared from Ti film deposited at 600 ° C had stronger adhesion to the substrate compared with that prepared from Ti film deposited at room temperature. The as-prepared TiO₂ nanowhiskers were single crystalline anatase and were the result of transformation of Ti into Na₂Ti₂O₄(OH)₂ and H₂Ti₂O₅·H₂O. The nanowhiskers took shape during the hydrothermal synthesis, preferably oriented parallel to (100) crystal face of Na₂Ti₂O₄(OH)₂, and experienced splitting conversion from nanobelts to nanowire harnesses and nanowires. The formation of vertical nanowhisker films was ascribed to a cooperative effect of the dilute NaOH solution and the higher hydrothermal temperature (220 ° C). The photoelectrochemical properties of the films were investigated in Na₂SO₄ solution, and the results showed that the as-prepared TiO₂ nanowhisker film exhibited better photoelectrochemical properties than those of zero-dimensional nanoparticle films and two-dimensional nanobelt films, indicating a good potential for practical application.