pH值、离子强度和粒径对氧化石墨烯稳定性的影响
The effects of pH, ionic strength and particle size on the stability of graphene oxide
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摘要: 氧化石墨烯(Graphene oxide,GO)表面具有丰富的官能团和较高的比表面积,能够作为膜材料应用于膜分离技术.然而,目前合成GO的技术很难保证其横向尺寸的均一性.此外,GO在自然水环境中分散性的稳定性受环境中pH值和离子强度的影响.本文研究了横向尺寸、pH值和离子强度对GO表面双电层电荷或结构组装所需的相互作用力的影响.从原位原子力显微镜(Atomic force microscope,AFM)获得的力-距离曲线(F-D)可以看出,溶液条件对DLVO力的作用.GO的双电层静电斥力随着pH值的升高而增大,这可能是由于表面官能团的电离作用增强所致.但随着离子强度的增加,双电层斥力减小,得到的数据与DLVO理论一致.通过Zeta电位和开尔文探针力显微镜(Kelvin probe force microscopy,KPFM)测量,确定了氧化石墨烯片层表面电荷的不均匀性.Abstract: High specific surface area and abundance of functional groups have facilitated the potential application of graphene oxide(GO) as a suitable material for membrane technology. However, synthesis techniques have not ensured the uniformity of GO transverse size required for membrane generation. In addition, poly-dispersity of GO in natural water attributed to variation in stability of GO as a function of pH and ionic strength. In this article, we studied the role of transverse size and pH and ionic strength on GO's electric double layer charge or interaction forces required for designing assembled structures. The role of solution parameters on DLVO forces were identified from the force-distance curve (F-D) obtained from in situ Atomic force microscope (AFM). The electrostatic repulsive force on GO tended to increase with the rise in pH possibly due to enhance ionization of the surface functional moieties. However, increasing ionic strength reduced the electrical double layer repulsive force and the obtained data was in coherence with DLVO theory. Particle size-dependent surface charge inhomogeneity of GO-platelets were determined from zeta potential and Kelvin probe force microscopy (KPFM) measurements.
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Key words:
- graphene oxide /
- force curve /
- electrical double layer
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