蒙脱石层电荷密度对其二维纳米片剥离的影响

Effect of Layer Charge Density on the Exfoliation of Montmorillonite to Prepare Two-Dimensional Nanosheets

以2种典型不同层电荷密度的蒙脱石为研究对象,通过烷基铵法测定了2种蒙脱石的层电荷密度,分别为0.342和0.439。研究了层电荷密度对蒙脱石二维剥离及其剥离后纳米片表面电性的影响。通过分子动力学模拟解释了层电荷密度对蒙脱石剥离二维纳米片和水化膨胀能力的影响机理。结果表明:层电荷密度低的蒙脱石具有更好的水化膨胀能力,更易剥离制备二维纳米片。层电荷密度高的蒙脱石剥离的二维纳米片单位面积的电负性更大。蒙脱石层电荷密度越低,其晶层表面对水分子吸附作用越弱,层间阳离子水化能力更强,水化膨胀能力大,也解释了层电荷密度低的蒙脱石更易剥离成二维纳米片的原因。

Two typical montmorillonite samples,with layer charge densities of 0.342 and 0.439,measured by using alkylammonium method,were selected in this study.The effects of layer charge density on the two-dimensional(2D)exfoliation of montmorillonite and the surface electrical properties of the nanosheets after exfoliation were studied.The mechanisms of the exfoliation and hydration swelling ability of montmorillonite were explained using molecular dynamics simulation.It was found that montmorillonite with relatively low layer charge density exhibited stronger hydration and swelling ability and thus was easier to be exfoliated into 2D nanosheets.The exfoliated 2D nanosheets from the montmorillonite with higher layer charge density had larger electronegativity per unit area.The lower layer charge density of montmorillonite,the weaker adsorption of water molecules on the surface of montmorillonite crystal layer,the stronger interlayer cation hydration and greater hydration swelling ability,could be used to explain the fact that the montmorillonite with low layer charge density was more easily exfoliated into 2D nanosheets.