聚乙烯吡咯烷酮
化学
吸附
纳米颗粒
面(心理学)
动能
动力控制
化学工程
各向异性
结晶学
纳米技术
化学物理
物理化学
高分子化学
有机化学
材料科学
催化作用
五大性格特征
人格
心理学
量子力学
社会心理学
工程类
物理
作者
Zhifeng Chen,Ji Woong Chang,Choumini Balasanthiran,Scott T. Milner,Robert M. Rioux
摘要
Polyvinylpyrrolidone (PVP) is used in the synthesis of Ag nanoparticles (NPs) with controlled shape, most commonly producing cubes. The mechanism for shape control is unclear but believed by many to be caused by preferential binding of PVP to Ag(100) facets compared to Ag(111) facets and assumed by most to be the result of thermodynamic control, whereby facets with lower interfacial free energy predominate. To investigate this mechanism, we measured adsorption isotherms of PVP on different-shaped Ag NPs, to determine the thermodynamics of PVP adsorption to Ag(100) and Ag(111) facets. The equilibrium adsorption constant is independent of PVP molecular weight and depends only weakly on NP shape (and thus Ag facet). The equilibrium adsorption constant for PVP on Ag(111) (2.8 M-1) is about half that on Ag(100) (5 M-1). From a Wulff construction, this difference is not nearly enough to produce cubes via thermodynamic control. This result indicates the importance of kinetic control of the Ag nanoparticle shape by PVP, as has recently been proposed.
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