Self‐assembled colloidal crystals (CCs) or nanoparticle (NPs) superlattices have attracted significant attention due to their potential applications in many fields. However, due to the complex interactions that govern the self‐assembly, it is difficult to predict and control the superstructure organization of CCs. Herein, a facile yet effective way is demonstrated to fabricate oriented CCs from capillary assembly of polymer‐tethered gold NPs (AuNPs). Assembly mechanism of polymer‐tethered AuNPs and their superlattice structures are systematically studied by in situ small‐angle X‐ray scattering (SAXS) technology. The results show that the oriented CCs of polymer‐tethered AuNPs can be obtained upon solvent evaporation in a capillary tube and the oriented structure is mainly determined by the chain length of polymer ligands and size of AuNPs. Assembly of AuNPs tethered by short‐chain ligand can result in oriented face‐centered cubic (fcc) superlattice, whereas AuNPs tethered by long‐chain ligand can assemble into an oriented body‐centered tetragonal (bct) superlattice structure. Interestingly, in situ SAXS study shows that for the sample of bct superlattice structure, a transformation from fcc to bct superlattice upon solvent evaporation is observed, which strongly depends on chain length of ligands. This work provides a useful guide for polymer‐tethered AuNPs to prepare orientation colloidal crystals.

The two-dimensional (2D) superlattice obtained by self-assembly of gold nanoparticle (NPs) at the air−liquid interface shows a wide range of potential applications in catalysis, sensing, electronic storage, and molecular recognition. However, the dynamic assembly process of the gold NPs at the air−liquid interface is still unclear. In this study, gold NPs grafted with thiolterminated polystyrene homopolymers (AuNPs@PS) were used as the assembly unit, and the 2D superlattice of AuNPs@PS was prepared by spreading and evaporating the AuNPs@PS toluene suspension at the air/diethylene glycol interface. The effects of polymer chain length, grafting density, and toluene vapor atmosphere on the microstructure of the superlattice were investigated as well. The microstructural evolution process of the AuNPs@PS superlattice at the air/diethylene glycol interface was monitored by the in situ grazing incident small-angle X-ray scattering (GISAXS) technique. The results demonstrate that the transition of longchain polymer-tethered NPs from random packing to face-centered-cubic packed superlattice followed by two-dimensional hexagonal packing can be observed under a toluene vapor atmosphere. Additionally, by varying the polymer chain length and solvent vapor atmosphere, the spreading rate and superlattice interparticle spacing can be well mediated. This work provides a useful guide to prepare an ordered 2D superlattice with polymer-tethered inorganic NPs.

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