【作者】 黄博达；

【导师】 夏曰源；

【作者基本信息】 山东大学 ， 光学工程， 2005， 博士

【摘要】 纳米材料与器件作为21世纪最重要的纳米科学与技术的分支,近年来得到了飞速的发展,显现出巨大的潜力和生命力。目前这一交叉学科已成为学术界最为前沿的研究领域之一,也是各国投入巨资极力发展的未来科学技术的制高点。在各种新兴的纳米材料中,碳纳米管以其特殊的结构、优良的性能、极高的稳定性受到了非常广泛的关注。而它所具有的各种独特性质在显示出无穷魅力的同时,也造就了许多新概念和新技术。 碳纳米管作为一种一维管状分子,可以视作由石墨片卷曲而成。这种独特的结构使其具有极高的表面积,对气体、液体等分子表现出较强的吸附性能;同时其管状空腔具有较大的容积,能够作为高效的分子存储介质。研究发现,通过毛细作用,碳纳米管可以将氢气等气体分子吸入并存储在管内。通过提高储氢量,碳管有可能在未来成为氢燃料的重要载体。 除了氢等气体分子外,其他分子或者溶液,以及DNA、蛋白质等生命物质也能够被吸附到碳纳米管之中。在研究这些吸附和输运现象时,水的作用是人们最关注的。水分子广泛存在于自然环境、化学试剂以及生物体中。研究证明,水分子对于维持生物细胞的输运畅通与电化学势平衡发挥着至关重要的作用。这些跨膜的蛋白质输运通道与碳纳米管的管状结构有相似之处。作为一种研究生物化学反应的基本模型,碳纳米管中的生命分子和溶液的传输是揭示众多未知生命现象的重要途径。 将碳纳米管作为分子传输通道的应用前景是十分广阔的。在纳米机械制造领域,拥有高机械强度的碳纳米管可以被用来构建基本的流体运送管网。在纳米医学领域,可以用碳纳米管探针来进行分子传输,如核酸、蛋白质或其他化学物质,甚至将来有望实施细胞手术,比如将药物直接送达癌细胞的细胞核内部。目前,日本已经成功的利用附有碳纳米管探针的原子力显微镜(AFM)观察活细胞的核子,并使纳米探针穿透细胞膜和核膜,直接到达细胞核。这就为更精确、更有效地杀灭癌细胞创造了条件。然而在这些应用中,我们面临的一个突出问题就是如何有效地对碳纳米管中的流体进行控制。纳米量级的微观物更多还原

【Abstract】 Nanomaterial and Nanodevice is one of the most important fields of nano science and technology in the 21th century, the development of which has got great promotion in recent years. Now, this cross-disciplinary field has been the most important frontier research subject receiving huge number of investment all over the world. Among nanomaterials, carbon nanotubes attract particular research attentions benefiting from its unique properties.Conceptually, carbon nanotubes can be formed by rolling up graphite sheets into tubular structures. This unique structure leads to high surface area with high adsorbability to gas, liquid and other molecules. Scientists found that carbon nanotubes can adsorb hydrogen and other gas molecules into their open cages by capillary filling. High capacity of gas adsorption will facilitate the applications of carbon nanotube acting as molecular storage and carriers of hydrogen fuel cell.Besides gases, other molecules and solutions, including DNA and protein, can be adsorbed into the cavity of carbon nanotubes. The most important agent in these processes is the most common solvent in nature, water. Water is widespread in natural environment, chemical reagents, and all living cells. It was proved that water molecules take an important role in maintaining the unblocked transport and the chemical potential balance near the cell membranes. Carbon nanotubes are very similar to these cross-membrane channels of living tissues, which can be used as the model for the study of biochemical interactions to reveal the unknown phenomena in nano-world and biosystems.The future of using carbon nanotubes as the molecules transport channels is very attractive. In nano-manipulate and nano-manufacture fields, carbon nanotubes can be built up into interlaced pipe networks. In the applications of nano-medicine, carbon nanotube probes can be used to transport nucleic acid, protein, and other chemical molecules, in order to deliver drugs into cells directly. Recently, Japanese scientistshad achieved this goal.However, the crucial problem in these applications is how to control the nanofluid inside carbon nanotubes. If we can not find an effective way to master the molecules in nanotubes, the success of molecules transportation devices will be impossible. Previous studies in the world did not deal well with it.Based on deepgoing analyses of molecular interactions, we proposed the "Controllable Transport Channel of Water NanofluicT concept, a way of controlling the transport of nanofluid through single-walled carbon nanotubes (SWNTs). By modifying the net charge of carbon nanotubes, we achieved the goal of controlling the transport properties of polar water molecules inside the carbon nanotubes. We also find the "Water Nanotubes" structures inside and outside carbon nanotubes, formed at room temperature. Recently, the model we proposed has been proved by experiments.Since carbon nanotubes can adsorb gas and liquid, the similar capillary filling of SWNTs should occur in the case of fused ionic crystals in liquid state. Then the recrystallization process of crystal molecules under special confinement from the carbon nanotubes during the cooling process will be a very important issue to investigate. For many reasons, experimental studies about these materials mainly focused on the crystals with heavy species. With the aid of supercomputers, we used ab initio quantum chemical method to calculate the interactions in the Carbon Nanotube-NaCl Crystal Complexes (CNNCC) for carbon nanotubes with various diameters and chiralities. Analyses of the dynamic interactions in the complex will provide essential information for experimentally exploring the potential applications of this material. Besides the dynamics simulations, we also computed the electronic properties and light absorption performance of the CNNCC.The following is the content list of key results of this dissertation.Chapter 4.In the works of this chapter, we study the interactions between various carbon nanotubes with different charges and water molecules, by combining the methods of Classical Molecular Dynamics Simulation and ab initio quantum chemical theory.We find that water molecules can be adsorbed into the cavity of opened carbon nanotubes, displaying polarized orientations. The ’Water Nanotubes" are formed inside and outside the carbon nanotubes with regular structures and regular density distributions.The electric field produced by the charged carbon nanotube makes the motion behavior of water molecules modulated, acting as the Transport Speed Regulator to control the penetration properties of water inside the carbon nanotube channels. These results are also very important for investigations of the liquid penetration and chemical potential balance of the pores or channels in biosystems and other related aqueous systems. The electron density distributions are also investigated by using ab initio quantum chemical method.Chapter 5.By investigating the interactions between single-walled carbon nanotubes charged with different charges and fused NaCl crystals, we find that the fused NaCl can fill up the cavity of carbon nanotubes. When the system is cooled down, the NaCl recrystallize into crystals and form the CNNCC. In this process, confinement from the carbon nanotube makes the NaCl crystal deformed remarkably, with the wall of the SWNT less deformed.However, NaCl inside the negatively charged carbon nanotubes can not form the normal simple cubic crystal structures. Instead, confined "Multi-walled NaCl Nanotubes" are formed. This structure is composed of alternated Na tubes and Cl tubes, which is totally different from the normal NaCl crystal structure.Chapter 6.Based on ab initio quantum chemical theory, we analyzed the dynamics properties and electronic structures of the CNNCC. It is found that the same NaCl crystal can be contained by carbon nanotubes with various diameters and types. Under the confinement from carbon nanotubes, NaCl crystals can represent stretchedor squashed type. In the deforming process, carbon nanotubes affect the Na+ ions greater than the Cl" ions. We point out that the simple van der Waals model cannot describe all the subtle forces in these systems. We also analyzed the key electronic properties of this complex by the computations of the band structure, the PDOS, and the density distributions of electrons.Chapter 7.In the works of this chapter, we used more accurate CI theory in conjunction with effective semi-empirical method to calculate the excited states and optical absorption properties of the CNNCC. Our results show that the confined NaCl ionic crystal can modulate substantially the optical absorption properties of carbon nanotube. Interactions between carbon nanotubes with different diameters and the confined NaCl crystals lead to different optical spectra. The results may promote researches on applications of the CNNCC structures on the field of the tunable infrared detector and the tunable polarizer device.更多还原