Redoxable nanosheet crystallites of MnO2 derived via delamination of a layered manganese oxide
Redoxable nanosheet crystallites of MnO2 derived via delamination of a layered manganese oxide
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DOI：
10.1021/ja021364p
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发表时间：
2003-03-26
影响因子：
15
通讯作者：
Watanabe, M
中科院分区：
文献类型：
--
作者：
Omomo, Y;Sasaki, T;Watanabe, M
本文报道了层状质子锰氧化物H0.13MnO2.0.7H（2）O在四丁基氢氧化铵（TBA）溶液中的溶胀和剥离行为以及单层二维MnO 2微晶的形成和表征。在低剂量的TBA离子，层状锰氧化物被观察到进行正常的插层，产生一个TBA插层相的画廊高度为1.25 nm。在大量过量的TBA离子的情况下，发生渗透溶胀，产生3.5-7 nm的非常大的片间分离。在中间TBA浓度范围内，样品表现出广泛的X-射线衍射曲线与叠加的衍射特征，由于插层和渗透溶胀。通过以不同的速度将混合物搅拌两次来分离负责宽轮廓的组分，并且将回收的胶体鉴定为一堆MnO 2纳米片，对应于前体层状氧化锰的单个宿主层。通过透射电子显微镜和原子力显微镜的观察发现，具有高的二维各向异性，横向尺寸为亚微米，厚度约为0.8 nm。纳米片表现出宽的光学吸收，在374 nm处具有峰值（λ = 1.13 × 10（4）mol（-1）dm（3）cm（-1））。胶态MnO 2纳米片的重新堆叠过程之后是在95%的相对湿度下老化胶体。由于剥离片的宽衍射图案随时间减弱，并最终分解成两个明显不同的轮廓，这归因于片间间距为1.72 nm的TBA插层化合物和在非常早期阶段具有> 10 nm的膨胀溶胀水合物。随着干燥的进行，前一相变得更加丰富，而层间距离没有变化，而后一相的溶胀度逐渐降低至2.7 nm，在进一步老化时保持不变。随后在较低湿度下干燥使2.7nm相塌陷。通过在150 ℃下加热使所得的单一1.72 nm相脱水以产生具有1.3 nm的收缩层间距的相。
This paper reports on the swelling and exfoliation behavior of a layered protonic manganese oxide, H0.13MnO2.0.7H(2)O, in a solution of tetrabutylammonium (TBA) hydroxide and the formation and characterizations of unilamellar two-dimensional crystallites of MnO2. At low doses of TBA ions, layered manganese oxide was observed to undergo normal intercalation, yielding a TBA intercalated phase with a gallery height of 1.25 nm. With a large excess of TBA ions, osmotic swelling occurred, giving rise to a very large intersheet separation of 3.5-7 nm. In an intermediate TBA concentration range, the sample exhibited a broad X-ray diffraction profile with superimposed diffraction features due to intercalation and osmotic swelling. The component responsible for the broad profile was isolated by centrifuging the mixture twice at different speeds, and the recovered colloid was identified as a pile of MnO2 nanosheets, corresponding to the individual host layer of the precursor layered manganese oxide. Observations by transmission electron microscopy and atomic force microscopy revealed high two-dimensional anisotropy with a lateral dimension of submicrometers and a thickness of similar to0.8 nm. The nanosheet exhibited broad optical absorption with a peak at 374 nm (epsilon = 1.13 x 10(4) mol(-1) dm(3) cm(-1)). The restacking process of the colloidal MnO2 nanosheets was followed by aging the colloid at a relative humidity of 95%. The broad diffraction pattern due to the exfoliated sheets weakened with time and eventually resolved into two sharp distinct profiles attributable to a TBA intercalation compound with an intersheet spacing of 1.72 nm and an osmotically swollen hydrate with > 10 nm at a very early stage. As drying progressed, the former phase became more abundant without a change in interlayer distance, while the degree of swelling of the latter phase gradually decreased to 2.7 nm that remained unchanged on further aging. Subsequent drying at a lower humidity collapsed the 2.7 nm phase. The resulting single 1.72 nm phase was dehydrated by heating at 150 degreesC to produce a phase with a contracted interlayer spacing of 1.3 nm.