Vakil Parth N, Hardy David A, Strouse Geoffrey F
Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States.
ACS Nano. 2018 Jul 24;12(7):6784-6793. doi: 10.1021/acsnano.8b01992. Epub 2018 Jun 21.
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)), 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.
随着各向异性纳米结构的重要性以及表面在催化、磁光和电磁干扰屏蔽等应用中的作用不断提升，需要为这类纳米结构开发高效且经济的合成路线。本文描述了循环微波功率在快速合成高度分支的纯相面心立方晶体镍多脚纳米结构中的应用，该结构的多脚占比超过99%。通过循环控制输送到反应混合物的功率，能够对金属纳米结构的生长动力学实现卓越控制，从而形成由不同纵横比的臂组成的多脚结构。在由乙酰丙酮镍（Ni(acac)）、油胺（OAm）和油酸（OAc）组成的简单反应体系中，在环境条件下，通过对镍纳米种子上的（111）外延生长角进行选择性加热，几分钟内即可形成多脚结构。角部的选择性加热通过“避雷针”效应导致沿〈111〉方向的自催化生长加速。其长度与微波（MW）开启循环的长度和次数成正比，而核心尺寸则由连续的微波功率输送控制。本文还探讨了材料合成过程中加热模式（循环加热与可变功率加热与对流加热）的作用，从而提出了一种关于循环微波能量如何实现快速多脚演化的机制。
