石墨烯、二氧化钛纳米线组装体的功能化设计及可控合成

发布时间：2019-07-02 10:19

【摘要】：以一维纳米纤维、纳米棒、纳米管等几何形貌为代表的低维纳米结构体系蕴含丰富多彩的化学、物理现象,一直是材料领域的研究前沿和热点。由于单一材料已然无法突破性能上的限制,对它们进行有效集成、组装是实现性能突破的有效途径。本文围绕石墨烯、Ti02纳米线的有序组装和可控合成,获得一类新颖的二维还原氧化石墨烯(RGO)／钛酸纳米线网状滤膜,在连续流反应中,对水中污染物吸附性能优良。本文还可控制备了新型一维RGO/TiO2纳米线,创新性地开展了对单根纳米线的电学性能的探索性研究。主要内容包括如下：(1)采用超声破碎法对改性Hummer法制备的氧化石墨烯(GO)大小进行精细调控,GO大小由2.3 μm逐渐降低0.5 μm以下。随着超声破碎增加至32min, GO发生还原反应导致生成RGO。因此,本文将超声破碎的时间优化为16 min,此时GO大小小于0.5 gm,并保持氧化状态,便于后续开展与Ti02的组装工作。(2)以P25为前驱物,采用水热法可控合成钛酸纳米线,其生长机理为：i)在水热反应,Ti02颗粒首先发生熟化,即较小粒径的颗粒逐渐溶解,较大粒径的颗粒逐渐长大,同时NaOH溶液中的OH-和H20进入Ti02晶粒并与晶格中的钛原子或氧原子反应,生成钛羟基,导致Ti02颗粒酥松多孔,逐渐形成多孔大直径球状物。ii)随着反应的进行,由于Na+离子的插层作用,生成钛酸钠,在球状颗粒表面形成钛酸钠纳米带,片层不断往外延伸生长,最终导致球体瓦解,剩下钛酸钠纳米带。iii)在劈裂机理作用下,钛酸钠片层发生割裂,形成有序的纳米线束形态,超声分散后,线束中纳米线分离,最终形成纳米线。此外,通过精细调控水热反应的碱种类、水热时间以及酸洗条件,获得了四种不同形貌的钛酸纳米材料：多孔纳米球、纳米带、纳米线、纳米管。将大小不同的石墨烯,按照不同配比与钛酸钠纳米线进行复合,复合生成“海胆状”、“交织膜状”、钛酸纳米管与氧化石墨烯有序交织状的复合物。(3)将钛酸纳米线与GO进行可控组装,获得二维(RGO)／钛酸纳米线网状滤膜。其组装机理为：i)在以范德华力为主的非共价键作用下,GO进攻钛酸纳米线；ii) GO片自发卷曲,包覆在一根或相邻的多根钛酸纳米线表面；iii)加入水合肼后,GO被还原为RGO,为减少的表面自由能,不同纳米线上的RGO相互吸引；在节点处的RGO吸引更多在溶液中游离的RGO至表面,使得交联点的RGO增厚,交联更加稳固。最终,形成二维RGO／钛酸纳米线网状膜。(4)设计了一套新颖的微滤成膜装置,由注射器、微量进样器、滤头组成。通过精细调控成膜过程的流速、体积、压力、时间等变量,使钛酸纳米线和RGO快速、均匀组装成膜。利用此装置制备的二维RGO/钛酸纳米线网状滤膜表面平滑、颜色均匀,且可自我支撑,在多次弯曲后,仍保持滤膜结构完整。选用罗丹明B的水溶液作为模型,RGO/钛酸纳米线滤膜,脱色率高达98%以上,可高效去除水溶液中的有机污染物。其中,钛酸纳米线作为骨架支撑石墨烯并有效避免其团聚,石墨烯裸露丰富的吸附活性位,发挥高效的吸附作用。该滤膜在吸附饱和后,采用次氯酸水溶液去除被吸附的有机物,可获得再生。(5)采用静电纺丝法制备RGO/TiO2纳米线,在透射电子显微镜(TEM)腔室中搭建单根RGO/TiO2纳米线电学测试平台,采用原位电学表征技术,成功测量到单根纤维的整流曲线。通过多次通电,观察到纳米线微观结构的变化规律。这对于后期的研究中,一维纤维的电学性能的数据分析有着重要的意义。
[Abstract]:The low-dimensional structure system represented by the geometrical morphology of one-dimensional nano-fiber, nano-rod, nanotube and the like contains rich and colorful chemical and physical phenomena, and has been a leading edge and a hot spot in the field of materials. The effective integration and assembly of single material is an effective way to achieve the breakthrough of performance. In this paper, a new type of two-dimensional redox graphene (RGO)/ nano-wire mesh filter is obtained by the ordered assembly and controlled synthesis of the graphene and Ti02 nanowires, and the adsorption performance of the pollutants in the water is excellent in the continuous flow reaction. In this paper, a new one-dimensional RGO/ TiO2 nanowire is also controlled, and an exploratory study on the electrical properties of a single nanowire has been developed. The main contents are as follows: (1) The size of the oxidized graphene (GO) prepared by the modified Hummer method is finely controlled by adopting the ultrasonic crushing method, and the size of the GO is gradually reduced by less than 0.5. m As the ultrasonic crushing increased to 32 min, the reduction reaction of GO resulted in the formation of RGO. Therefore, the time of ultrasonic crushing is optimized to be 16 min. At this time, the size of GO is less than 0.5gm, and the oxidation state is kept, so that the assembly work with Ti02 can be carried out. (2) adopting a hydrothermal method to controllably synthesize the titanate nanowire with the P25 as a precursor, the growth mechanism of which is: i) in the hydrothermal reaction, the Ti02 particles are first cured, that is, the particles of the smaller particle size are gradually dissolved, and the particles of the larger particle size gradually grow, And the OH-and H20 in the NaOH solution enter the Ti02 crystal grain and react with the titanium atom or the oxygen atom in the crystal lattice to generate the titanium hydroxyl group, so that the Ti02 particles are loose and porous, and the porous large-diameter ball is gradually formed. Ii) as the reaction proceeds, the sodium titanate is formed due to the intercalation action of the Na + ions, the sodium titanate nano-band is formed on the surface of the spherical particles, the sheet layer continuously extends out and grows, and finally the sphere is broken, and the sodium titanate nano-band is left. And iii) under the action of the splitting mechanism, the sodium titanate layer is separated to form an ordered nanowire bundle form, and after the ultrasonic dispersion, the nanowires in the wire harness are separated, and finally the nano-wire is formed. In addition, four kinds of nano-materials with different shapes are obtained by finely adjusting the alkali kind, the hydrothermal time and the acid-washing condition of the hydrothermal reaction, and the porous nano-spheres, the nanoribbons, the nanowires and the nanotubes are obtained. The graphene which is different in size is compounded with the sodium titanate nano wire according to different proportions to generate a composite of the "sea urchin", the "interweave film", the titanate nano tube and the graphene oxide ordered interweave. And (3) carrying out controllable assembly of the titanate nano wire and the GO to obtain a two-dimensional (RGO)/ titanate nanowire mesh filter membrane. The assembly mechanism of the GO is as follows: i) the GO attacks the titanate nanowire under the non-covalent interaction with the Van der Waals force; ii) the GO sheet is spontaneously rolled and coated on one or adjacent multiple titanate nano wire surfaces; and iii) after the water is added, the GO is reduced to RGO, so that the reduced surface free energy can be reduced, The RGO on different nanowires is attracted to each other; the RGO at the node attracts more free RGO to the surface in the solution, so that the RGO of the cross-linking point is thickened and the cross-linking is more stable. And finally, a two-dimensional RGO/ titanate nanowire mesh film is formed. And (4) a novel microfiltration membrane-forming device is designed, which consists of a syringe, a micro sample injector and a filter head. Through the fine regulation of the flow rate, volume, pressure, time and other variables of the film-forming process, the titanate nano-wire and the RGO are quickly and uniformly assembled into a film. The two-dimensional RGO/ titanate nano-wire mesh filter membrane prepared by the device is smooth in surface, uniform in color and self-supporting, and the membrane structure is still intact after multiple times of bending. The aqueous solution of rhodamine B is used as a model, the RGO/ titanate nano-wire filter membrane and the decoloring rate are as high as 98%, and the organic pollutants in the aqueous solution can be effectively removed. In which, the titanate nanowire is used as a framework for supporting the graphene and effectively avoids the agglomeration of the graphene, and the graphene has rich adsorption activity bits and has an efficient adsorption effect. After the filter membrane is saturated, the adsorbed organic matter is removed by using an aqueous solution of hypochlorous acid and can be regenerated. (5) RGO/ TiO2 nanowires were prepared by electrostatic spinning, and a single RGO/ TiO2 nanowire electrical test platform was set up in a transmission electron microscope (TEM) chamber, and the rectification curve of a single fiber was successfully measured by in-situ electrical characterization technology. The change of the micro-structure of the nano-wire was observed by multiple times of power-on. This is of great significance for the data analysis of the electrical properties of one-dimensional fiber in the later study.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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