Li Zhiwei, Qian Chang, Xu Wenjing, Zhu Chenhui, Yin Yadong
Department of Chemistry, University of California, Riverside, CA 92521, USA.
Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, USA.
Sci Adv. 2021 Sep 10;7(37):eabh1289. doi: 10.1126/sciadv.abh1289.
Morphological and magnetic anisotropy can be combined in colloidal assembly to create unconventional secondary structures. We show here that magnetite nanorods interact along a critical angle, depending on their aspect ratios and assemble into body-centered tetragonal colloidal crystals. Under a magnetic field, size-dependent attractive and repulsive domains develop on the ends and center of the nanorods, respectively. Our joint experiment-computational multiscale study demonstrates the presence of a critical angle in the attractive domain, which defines the equilibrium bonding states of interacting rods and leads to the formation of non–close-packed yet hard-contact tetragonal crystals. Small-angle x-ray scattering measurement attributes the perfect tetragonal phase to the slow assembly kinetics. The crystals exhibit brilliant structural colors, which can be actively tuned by changing the magnetic field direction. These highly ordered frameworks and well-defined three-dimensional nanochannels may offer new opportunities for manipulating nanoscale chemical transformation, mass transportation, and wave propagation.
形态学和磁各向异性可以在胶体组装中结合起来，以创造出非常规的二级结构。我们在此表明，磁铁矿纳米棒会沿着一个临界角相互作用，这取决于它们的纵横比，并组装成体心四方胶体晶体。在磁场作用下，纳米棒的端部和中心分别形成了与尺寸相关的吸引域和排斥域。我们联合进行的实验-计算多尺度研究表明，吸引域中存在一个临界角，它定义了相互作用纳米棒的平衡键合状态，并导致形成非密排但硬接触的四方晶体。小角X射线散射测量将完美的四方相归因于缓慢的组装动力学。这些晶体呈现出明亮的结构色，可以通过改变磁场方向进行主动调节。这些高度有序的框架和定义明确的三维纳米通道可能为操纵纳米级化学转化、质量传输和波传播提供新的机会。
