Quantitative analysis of the role played by poly(vinylpyrrolidone) in seed-mediated growth of Ag nanocrystals.
Quantitative analysis of the role played by poly(vinylpyrrolidone) in seed-mediated growth of Ag nanocrystals.
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DOI：
10.1021/ja210047e
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发表时间：
2012-01-25
影响因子：
15
通讯作者：
Xia, Younan
中科院分区：
文献类型：
--
作者：
Xia, Xiaohu;Zeng, Jie;Oetjen, L. Kyle;Li, Qingge;Xia, Younan
本文提出了一个定量分析的作用，聚乙烯吡咯烷酮（PVP）在种子介导的银纳米晶体的生长。以{100}晶面包裹的银纳米立方体为晶种，根据溶液中PVP的浓度，得到的纳米晶体可以具有不同的形状。如果浓度高于临界值，则种子简单地生长成仍被{100}面包围的较大立方体。当浓度低于临界值时，种子将演变成由{100}和{111}面混合包围的立方八面体，并最终完全被{111}面覆盖的八面体。结合两种测量方法的结果，我们得到了PVP在Ag（100）表面上的覆盖密度：i）在固定PVP初始浓度下，跟踪立方晶种的生长，以确定{111}面开始出现在表面上的时间;和ii）使立方体晶种在降低的PVP初始浓度下生长，以观察在何种浓度下{111}从一开始就出现了小面。我们可以计算的PVP的覆盖密度的差异，在PVP的浓度和总表面积的银纳米立方体之间的这两个样品。对于边长为40 nm的立方晶种，发现分子量为55，000和10，000 g/mol的PVP的覆盖密度分别为140和30个重复单元/nm 2。当使用100 nm的Ag立方体作为晶种时，这些值分别略微下降到100和20个重复单元/nm 2。
This article presents a quantitative analysis of the role played by poly(vinyl pyrrolidone) (PVP) in seed-mediated growth of Ag nanocrystals. Starting from Ag nanocubes encased by {100} facets as the seeds, the resultant nanocrystals could take different shapes depending on the concentration of PVP in the solution. If the concentration was above a critical value, the seeds simply grew into larger cubes still enclosed by {100} facets. When the concentration fell below a critical value, the seeds would evolve into cuboctahedrons enclosed by a mix of {100} and {111} facets and eventually octahedrons completely covered by {111} facets. We derived the coverage density of PVP on Ag(100) surface by combining the results from two measurements: i) cubic seeds were followed to grow at a fixed initial concentration of PVP to find out when {111} facets started to appear on the surface; and ii) cubic seeds were allowed to grow at reduced initial concentrations of PVP to see at which concentration {111} facets started to appear from the very beginning. We could calculate the coverage density of PVP from the differences in PVP concentration and the total surface area of Ag nanocubes between these two samples. The coverage density was found to be 140 and 30 repeating units per nm2 for PVP of 55,000 and 10,000 g/mol in molecular weight, respectively, for cubic seeds of 40 nm in edge length. These values dropped slightly to 100 and 20 repeating units per nm2, respectively, when 100-nm Ag cubes were used as the seeds.
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