Synthesis of Highly Uniform Nickel Multipods with Tunable Aspect Ratio by Microwave Power Control
Synthesis of Highly Uniform Nickel Multipods with Tunable Aspect Ratio by Microwave Power Control
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DOI：
10.1021/acsnano.8b01992
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发表时间：
2018-07-01
期刊：
影响因子：
17.1
通讯作者：
Strouse, Geoffrey F.
中科院分区：
文献类型：
--
作者：
Vakil, Parth N.;Hardy, David A.;Strouse, Geoffrey F.
随着各向异性纳米结构的重要性和表面的作用在催化、磁光和电磁干扰屏蔽等应用中不断上升，需要针对此类纳米结构的高效且经济的合成路线。该文章描述了循环微波功率在快速合成高度支化纯相面心立方晶体镍多脚纳米结构（多脚数量 >99%）中的应用。通过循环控制向反应混合物的功率输送，可以实现对金属纳米结构的生长动力学的卓越控制，从而形成由具有不同长宽比的臂组成的多足体。在环境条件下，通过在 Ni 纳米种子上的 (111) 过度生长角选择性加热，在由乙酰丙酮镍 (Ni(acac)(2))、油胺 (OAm) 和油酸 (OAc) 组成的简单反应体系中，在几分钟内形成多足结构。拐角处的选择性加热通过“避雷针”效应导致沿（111）方向加速自催化生长。长度与微波 (MW) 开启周期的长度和数量成正比，而磁芯尺寸则由连续 MW 功率传输控制。探索了材料合成过程中加热模式（循环、可变功率与对流加热）的作用，从而提出了循环微波能量如何允许快速多足进化的机制。
As the importance of anisotropic nanostructures and the role of surfaces continues to rise in applications including catalysis, magneto-optics, and electromagnetic interference shielding, there is a need for efficient and economical synthesis routes for such nanostructures. The article describes the application of cycled microwave power for the rapid synthesis of highly branched pure-phase face-centered cubic crystalline nickel multipod nanostructures with >99% multipod population. By controlling the power delivery to the reaction mixture through cycling, superior control is achieved over the growth kinetics of the metallic nanostructures, allowing formation of multipods consisting of arms with different aspect ratios. The multipod structures are formed under ambient conditions in a simple reaction system composed of nickel acetylacetonate (Ni(acac)(2)), oleylamine (OAm), and oleic acid (OAc) in a matter of minutes by selective heating at the (111) overgrowth corners on Ni nanoseeds. The selective heating at the corners leads to accelerated autocatalytic growth along the (111) direction through a "lightning rod" effect. The length is proprtional to the length and number of microwave (MW)-on cycles, whereas the core size is controlled by continuous MW power delivery. The roles of heating mode (cycling versus variable power versus convective heating) during synthesis of the materials is explored, allowing a mechanism into how cycled microwave energy may allow fast multipod evolution to be proposed.