Supercrystallographic Reconstruction of 3D Nanorod Assembly with Collectively Anisotropic Upconversion Fluorescence.

Deng, Kerong; Huang, Xin; Liu, Yulian; Xu, Lili; Li, Ruipeng; Tang, Ji; Lei, Qun-Li; Ni, Ran et al. · Nano Lett · 2020

basic_science · Level V

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Abstract

Constructing three-dimensional (3D) metamaterials from functional nanoparticles endows them with emerging collective properties tailored by the packing geometries. Herein, we report 3D supercrystals self-assembled from upconversion nanorods (NaYF<sub>4</sub>:Yb,Er NRs), which exhibit both translational ordering of NRs and orientational ordering between constituent NRs in the superlattice (SL). The construction of 3D reciprocal space mappings (RSMs) based on synchrotron-based X-ray scattering measurements was developed to uncover the complex structure of such an assembly. That is, the two main orthogonal sets of hexagonal close-packing (<i>hcp</i>)-like SLs share the [110]<sub>SL</sub> axis, and NRs within the SL possess orientational relationships of [120]<sub>NR</sub>//[100]<sub>SL</sub>, [210]<sub>NR</sub>//[010]<sub>SL</sub>, and [001]<sub>NR</sub>//[001]<sub>SL</sub>. Notably, these supercrystals containing well-aligned NRs exhibit collectively anisotropic upconversion fluorescence in two perpendicular directions. This study not only demonstrates novel crystalline superstructures and functionality of NR-based 3D assemblies but also offers a unique tool for deciphering a wide range of complex nanoparticle supercrystals.

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