Construction of Highly Ordered Lamellar Nanostructures through Langmuir-Blodgett Deposition of Molecularly Thin Titania Nanosheets Tens of Micrometers Wide and Their Excellent Dielectric Properties
Construction of Highly Ordered Lamellar Nanostructures through Langmuir-Blodgett Deposition of Molecularly Thin Titania Nanosheets Tens of Micrometers Wide and Their Excellent Dielectric Properties
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DOI：
10.1021/nn900104u
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发表时间：
2009-05-01
期刊：
影响因子：
17.1
通讯作者：
Sasaki, Takayoshi
中科院分区：
文献类型：
--
作者：
Akatsuka, Kosho;Haga, Masa-aki;Sasaki, Takayoshi
剥离的单层二氧化钛纳米片的Ti 0.87O2的横向尺寸为10-30 μ m的沉积层到不同的基板上通过Langmuir-Blodgett程序，以产生高度有序的层状纳米膜。分散在含有季铵离子作为支持电解质的水性悬浮液中的纳米片自发地漂浮在空气/液体界面处，并且它们在表面压缩后被成功地转移到基底上。纳米片的整齐平铺可以在优化的表面压力下实现。将由此获得的膜暴露于UV光以使基底表面亲水，这有助于单层沉积的稳定重复。通过UV-可见吸收光谱确认逐层生长，其显示由于纳米片的吸收带的逐渐增强。横截面透射电子显微镜图像可视化均匀沉积在基底表面上的纳米薄膜，并且在更高的放大倍数下清楚地分辨出逐层组装的纳米片的层状边缘。薄膜的X射线衍射数据显示出高达第七阶的尖锐基底反射，并且图案的Williamson-Hall分析表明，薄膜相对于X射线在整个厚度上是相干的，并且晶格应变非常小。此外，第一基底反射伴随着小的卫星峰，这是由劳厄干涉函数占。所有这些特征清楚地表明，形成了高度有序的层状纳米结构的二氧化钛纳米片可比的人工晶格薄膜通过现代气相沉积工艺生产。所获得的膜显示出上级介电和绝缘性能作为高度组织的膜纳米结构的反映。
Exfoliated unilamellar titania nanosheets of Ti0.87O2 with a lateral size of 10-30 mu m were deposited layer-by-layer onto various substrates by Langmuir-Blodgett procedure to produce a highly ordered lamellar nanofilms. The nanosheets dispersed in an aqueous suspension containing quaternary ammonium ions as a supporting electrolyte floated spontaneously at the air/liquid interface, and they were successfully transferred onto the substrate after surface compression. Neat tiling of the nanosheets could be realized at an optimized surface pressure. The film thus obtained was exposed to UV light to turn the substrate surface hydrophilic, which was helpful for stable repetition of monolayer deposition. Layer-by-layer growth was confirmed by UV-visible absorption spectra, which showed progressive enhancement of an absorption band due to the nanosheet. Cross-sectional transmission electron microscopy images visualized the ultrathin film homogeneously deposited on the substrate surface and a lamellar fringe of the layer-by-layer assembled nanosheets was clearly resolved at a higher magnification. X-ray diffraction data on the films showed sharp basal reflections up to the seventh order, and Williamson-Hall analysis of the pattern indicated that the film was coherent across the total thickness with respect to X-ray and that the lattice strain was extremely small. In addition, the first basal reflection was accompanied by small satellite peaks, which are accounted for by the Laue interference function. All these features clearly indicate the formation of a highly ordered lamellar nanostructure of the titania nanosheets comparable to artificial lattice films produced via modern vapor-phase deposition processes. The obtained films showed superior dielectric and insulating properties as a reflection of the highly organized film nanoarchitecture.