利用低温生长法制备水纳米团簇及二维冰
发布时间：2019-05-21 20:13
【摘要】：水是生命所依赖的最重要物质,无论是在自然界,还是在科学技术领域,水都具有重要的应用价值。水-固界面一直是材料、生命科学、物理和化学领域研究的热点,从基础研究的角度看,关于界面水的研究不仅有助于理解氢键的本质,还可以探索氢原子的迁移机制。此外,界面水还有助于加深对大气科学以及天体物理等方面的认识。本实验利用低温生长法,在低温扫描隧道显微镜(LT-STM)下研究了水分子在高定向裂解石墨(HOPG)表面的吸附生长。研究发现,在不同的覆盖度下,水分子在石墨表面表现出不同的结合方式。低覆盖度下,在石墨表面观察到了水分子二聚体、三聚体及不同结构的水分子团簇。受到石墨衬底的六角对称性影响,水分子团簇的结构多选择三角或六角对称分布。此外,由于石墨表面的疏水性,水分子在石墨表面表现出很好的迁移性,不容易直接生长得到水分子单体,我们通过对探针施加脉冲的方式在石墨表面观察到了单个水分子,并在液氦温度(4.7K)下看到了水分子单体的分子轨道。随着覆盖度的增加,在样品由液氮温度(78K)升到室温的过程中,水分子形成单分子层厚的二维水膜,其面内结构是非共边的六边形蜂窝状结构,类似于体材料的Ice-II相。根据水分子在石墨表面沉积量的不同,水膜尺寸也由几十纳米到几微米不等。此外,我们在二维水膜表面观察到了多种形式的莫尔条纹,表明水膜与石墨衬底之间存在非共度关系。通过傅立叶变换研究发现,二维水膜在石墨表面发生了转动,莫尔条纹随着转动角度的不同表现出不同的形式,这也证明了水与石墨衬底之间存在较弱的范德瓦尔斯力。
[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.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB383.1
[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.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB383.1
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1 高兴球,张开明,高而震;双原子气体分子在石墨表面——(0001)的吸附结构[J];应用科学学报;1989年04期
2 刘强,，
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