【摘要】：水是生命所依賴的最重要物質,無論是在自然界,還是在科學技術領域,水都具有重要的應用價值。水-固界面一直是材料、生命科學、物理和化學領域研究的熱點,從基礎研究的角度看,關于界面水的研究不僅有助于理解氫鍵的本質,還可以探索氫原子的遷移機制。此外,界面水還有助于加深對大氣科學以及天體物理等方面的認識。本實驗利用低溫生長法,在低溫掃描隧道顯微鏡(LT-STM)下研究了水分子在高定向裂解石墨(HOPG)表面的吸附生長。研究發(fā)現(xiàn),在不同的覆蓋度下,水分子在石墨表面表現(xiàn)出不同的結合方式。低覆蓋度下,在石墨表面觀察到了水分子二聚體、三聚體及不同結構的水分子團簇。受到石墨襯底的六角對稱性影響,水分子團簇的結構多選擇三角或六角對稱分布。此外,由于石墨表面的疏水性,水分子在石墨表面表現(xiàn)出很好的遷移性,不容易直接生長得到水分子單體,我們通過對探針施加脈沖的方式在石墨表面觀察到了單個水分子,并在液氦溫度(4.7K)下看到了水分子單體的分子軌道。隨著覆蓋度的增加,在樣品由液氮溫度(78K)升到室溫的過程中,水分子形成單分子層厚的二維水膜,其面內結構是非共邊的六邊形蜂窩狀結構,類似于體材料的Ice-II相。根據(jù)水分子在石墨表面沉積量的不同,水膜尺寸也由幾十納米到幾微米不等。此外,我們在二維水膜表面觀察到了多種形式的莫爾條紋,表明水膜與石墨襯底之間存在非共度關系。通過傅立葉變換研究發(fā)現(xiàn),二維水膜在石墨表面發(fā)生了轉動,莫爾條紋隨著轉動角度的不同表現(xiàn)出不同的形式,這也證明了水與石墨襯底之間存在較弱的范德瓦爾斯力。
[Abstract]:Water is the most important material on which life depends. Water has important application value both in nature and in the field of science and technology. Water-solid interface has always been a hot topic in the fields of material, life science, physics and chemistry. From the point of view of basic research, the study of interfacial water is not only helpful to understand the nature of hydrogen bond, but also to explore the migration mechanism of hydrogen atoms. In addition, interfacial water also helps to deepen the understanding of atmospheric science and Astrophysics. The adsorption growth of water molecules on the surface of highly directional cracked graphite (HOPG) was studied by low temperature scanning tunneling microscope (LT-STM) by low temperature growth method. It is found that water molecules exhibit different binding modes on graphite surface under different coverage. At low coverage, water dimer, trimer and water molecular clusters with different structures were observed on the surface of graphite. Due to the hexagonal symmetry of graphite substrate, the structure of water molecular clusters is triangular or hexagonal symmetry distribution. In addition, because of the hydrophobicity of graphite surface, water molecules show good mobility on graphite surface, so it is not easy to grow water molecular monomers directly. We observed a single water molecule on graphite surface by applying pulse to the probe. The molecular orbitals of water molecular monomers were observed at liquid Helium temperature (4.7 K). With the increase of coverage, when the sample rises from liquid nitrogen temperature (78K) to room temperature, water molecules form a two-dimensional water film with monolayer thickness, and its in-plane structure is non-concomitant hexagonal honeycomb structure, which is similar to the Ice-II phase of bulk material. According to the amount of water molecules deposited on graphite surface, the size of water film varies from tens of nanometers to several micrometers. In addition, many forms of moire fringes have been observed on the surface of two-dimensional water film, indicating that there is a non-cooperative relationship between water film and graphite substrate. Through Fourier transform, it is found that the two-dimensional water film rotates on the graphite surface, and the moire fringes show different forms with the different rotation angles, which also proves that there is a weak van der Waals force between water and graphite substrate.
【學位授予單位】：西南大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TB383.1

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1 高興球,張開明,高而震;雙原子氣體分子在石墨表面——(0001)的吸附結構[J];應用科學學報;1989年04期

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本文編號：2482359