超临界二氧化碳辅助构筑的乳液环境中制备二维层状材料及其功能化应用研究

发布时间：2018-10-25 17:53

【摘要】：二维层状材料在光电、传感、催化、机械、生物和能量储存等领域展现出了巨大的潜能。二维层状纳米材料的制备对于发挥其全面的性能起到至关重要的作用。主要方法有:外延生长法、水热法、化学气相沉积、微机械剥离法、液相超声剥离法、插层剥离法等。此外,超临界二氧化碳(SC CO2)由于具有高的扩散系数及低的表面张力也被应用于剥离二维层状材料。众所周知,在SC CO2和水的界面上引入表面活性剂或者纳米粒子能够形成乳液环境。通过改变CO2压力、温度、PH等影响因素,能够调控乳液的性质和界面的相行为。本文将层状材料引入到SC CO2构筑的乳液环境中来实现层状材料的高效剥离,并且研究了剥离出的二维层状材料分别在电化学、生物及机械方面的性能。主要内容如下:(1)在SC CO2构筑的Pickering乳液中剥离Mo S2及其在细胞荧光标定中的应用研究利用SC CO2、水以及Mo S2构筑形成Pickering乳液,通过高速搅拌在乳液中水和CO2界面上形成巨大的剪切力,实现Mo S2从块体材料上的剥离。在剥离过程中,乙醇作为共溶剂在剥离的效率上起到了很大的作用。此外,该方法制备的Mo S2纳米薄片展现了优异的光致发光性能,并且验证了其在生物细胞荧光标记领域展现出巨大的应用价值。(2)在由SC CO2/表面活性剂/水体系构筑的乳液微环境中剥离层状材料的研究在CO2和水之间引入表面活性剂PVP来构筑乳液微环境。改变CO2的压力能够产生强烈的驱动力来调节乳液微环境中的界面张力以及表面活性剂膜层的曲率。由于PVP必须能够紧紧吸附在层状材料的表面,表面活性剂膜层的弯曲可以克服层状材料间的范德华力,并驱动二维纳米薄片从块体材料表面的剥离。因此,本工作在CO2/PVP/H2O体系构筑的乳液微环境中成功剥离了石墨烯、Mo S2、WS2以及BN等典型的层状材料。而且,本工作也研究了CO2/PVP/H2O体系构筑的乳液的相行为以及解释层状材料在乳液微环境中剥离的机理。此外,也研究了CO2压力、乙醇/水比例以及初始粉末浓度对剥离效率的影响。(3)制备的二维层状材料在电化学、生物、机械等领域的应用研究本工作研究了制备的二维层状材料在电化学、生物、以及机械等方面的性能。首先,将剥离的石墨烯作为“墨水”刷在普通的A4纸上来制备成石墨烯薄膜,将其装配成超级电容器并测试其电化学性能,石墨烯展现了优异的电学性能。同时,将调控剥离的Mo S2的尺寸,得到尺寸小于120 nm的Mo S2纳米薄片,并将其作为荧光探针来进行荧光标定。在荧光标定前,测试了Mo S2的荧光性能以及对细胞的毒性,Mo S2都展现出了良好的性能。此外,利用剥离的BN纳米薄片制备了BN/PVA复合薄膜,并测试了复合薄膜的机械性能。实验结果显示,微量的BN的加入就可以明显增加PVA机械强度。
[Abstract]:Two-dimensional layered materials exhibit great potential in the fields of photoelectricity, sensing, catalysis, mechanical, biological and energy storage. The preparation of two-dimensional layered nanomaterials plays an important role in giving full play to their comprehensive properties. The main methods are as follows: epitaxial growth method, hydrothermal method, chemical vapor deposition, micromechanical stripping method, liquid phase ultrasonic stripping method, intercalation stripping method and so on. In addition, supercritical carbon dioxide (SC CO2) has been used to peel two-dimensional layered materials due to its high diffusion coefficient and low surface tension. It is well known that the introduction of surfactants or nanoparticles at the interface between SC CO2 and water can form an emulsion environment. By changing the pressure, temperature and PH of CO2, the properties of emulsion and the phase behavior of the interface can be regulated. In this paper, layered materials are introduced into the emulsion environment of SC CO2 to realize the efficient delamination of layered materials, and the electrochemical, biological and mechanical properties of the two dimensional layered materials are studied. The main contents are as follows: (1) stripping Mo S2 from Pickering emulsion constructed by SC CO2 and its application in cell fluorescence calibration; using SC CO2, water and Mo S2 to construct Pickering emulsion. A large shear force was formed on the interface between water and CO2 in emulsion by high speed stirring, and the stripping of Mo S2 from bulk material was realized. Ethanol, as a co-solvent, plays an important role in peeling efficiency during peeling. In addition, the Mo S2 nanocrystals prepared by this method exhibit excellent photoluminescence properties. It is proved that it has great application value in the field of biological cell fluorescence labeling. (2) the study of delamination of layered materials in the emulsion microenvironment constructed by SC CO2/ surfactant / water system introduced surface activity between CO2 and water. The property agent PVP was used to construct the microenvironment of emulsion. Changing the pressure of CO2 can produce a strong driving force to adjust the interfacial tension and the curvature of surfactant film in microemulsion environment. Because PVP must be able to adhere tightly to the surface of the layered material, the bending of the surfactant film can overcome the van der Waals force between the layered materials and drive the delamination of the two-dimensional nanosheet from the surface of the bulk material. Therefore, the typical layered materials such as graphene, Mo S2WS2 and BN were successfully stripped in the emulsion microenvironment constructed by CO2/PVP/H2O system. Moreover, the phase behavior of the emulsion constructed by CO2/PVP/H2O system and the mechanism of explaining the delamination of layered materials in the emulsion microenvironment were also studied in this work. In addition, the effects of CO2 pressure, ethanol / water ratio and initial powder concentration on the stripping efficiency were also studied. In this paper, the electrochemical, biological and mechanical properties of two-dimensional layered materials were studied. Firstly, graphene films were prepared by brushing the exfoliated graphene on ordinary A4 paper as "ink". The graphene films were assembled into supercapacitors and their electrochemical properties were tested. Graphene showed excellent electrical properties. At the same time, the size of the stripped Mo S2 was adjusted to obtain the Mo S2 nanocrystals with the size less than 120 nm, which was used as a fluorescence probe to carry out the fluorescence calibration. Before fluorescence calibration, the fluorescence properties and cytotoxicity of Mo S2 were tested. Mo S2 showed good performance. In addition, BN/PVA composite films were prepared by peeling BN nanocrystals and the mechanical properties of the composite films were tested. The experimental results show that the mechanical strength of PVA can be significantly increased by adding a small amount of BN.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TB383.2

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