Positively charged nanosheets derived via total delamination of layered double hydroxides
Positively charged nanosheets derived via total delamination of layered double hydroxides
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DOI：
10.1021/cm0510460
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发表时间：
2005-08-23
影响因子：
8.6
通讯作者：
Sasaki, T
中科院分区：
文献类型：
--
作者：
Li, L;Ma, RZ;Sasaki, T
通过将结晶良好的层状双氢氧化镁（LDH）硝酸盐直接分层，合成了横向尺寸为微米的带正电纳米片。甲酰胺对10 μ m大小的LDH晶体的作用导致透明溶液。从溶液中离心的胶状胶体上的X射线衍射测量检测到在小角度范围内的宽特征，同时完全失去前体结晶化合物的尖锐反射。宽分布与基于LDH结构计算的结构因子的平方非常相似，这为LDH晶体完全剥离成其单层提供了有力的证据。在氮气流中原位老化后，宽图案逐渐转化为尖锐的基底衍射图案，表明分子LDH纳米片的重新堆叠以恢复原始堆叠形式。通过透射电子显微镜和原子力显微镜的观察显示，分层的纳米片与几个微米的横向尺寸和0.8 nm的厚度。电子衍射数据和元素分析结果以及这些形态特征支持单层LDH片的形成。LDH纳米片可以组装层与阴离子聚合物，聚（苯乙烯4-磺酸钠）（PSS），到固体表面上，以产生纳米复合材料薄膜，证明其作为带正电荷的层状纳米块的有用性。纳米结构的多层组装体的形成被证实由逐步增强的UV吸光度由于PSS和X-射线衍射峰的演变显示出类似于2.0 nm的重复距离。
Positively charged nanosheets with a lateral dimension of micrometers have been synthesized by directly delaminating a well-crystallized Mg-Al layered double hydroxide (LDH) in the nitrate form. The action of formamide on LDH crystals 10 mu m in size led to a transparent solution. X-ray diffraction measurement on a glue-like colloid centrifuged from the solution detected a broad feature at small angular range, while completely losing the sharp reflections for the precursor crystalline compound. The broad profile was very similar to the square of the structure factor calculated based on the LDH structure, which provides strong evidence for the total exfoliation of the LDH crystals into their single sheets. Upon in situ aging in a stream of nitrogen gas, the broad pattern was gradually converted into a sharp basal diffraction pattern, indicating the restacking of molecular LDH nanosheets to restore the original stacked form. Observations by transmission electron microscopy and atomic force microscopy revealed delaminated nanosheets with a lateral size of several micrometers and a thickness of 0.8 nm. The electron diffraction data and elemental microanalysis results as well as these morphological features supported the formation of unilamellar LDH sheets. The LDH nanosheets could be assembled layer-by-layer with an anionic polymer, poly(sodium styrene 4-sulfonate) (PSS), onto the solid surface to produce ultrathin nanocomposite films, demonstrating their usefulness as a positively charged lamellar nanoblock. The formation of nanostructured multilayer assemblies was confirmed by the progressive enhancement of UV absorbance due to PSS and the evolution of X-ray diffraction peaks showing a repeating distance of similar to 2.0 nm.