Spiral Square Nanosheets Assembled from Ru Clusters

Spiral two-dimensional (2D) nanosheets exhibit unique physical and chemical phenomena due to their twisted structures. While self-assembly of clusters is an ideal strategy to form hierarchical 2D structures, it is challenging to form spiral nanosheets. Herein, we first report a screw dislocation involved assembled method to obtain 2D spiral cluster assembled nanosheets (CANs) with uniform square morphology. The 2D spiral Ru CANs with a length of approximately 4 μm and thickness of 20.7 ± 3.0 nm per layer were prepared via the assembly of 1-2 nm Ru clusters in the presence of molten block copolymer Pluronic F127. Cryo-electron microscopy (cryo-EM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) demonstrate the existence of screw dislocation in the spiral assembled structure. The X-ray absorption fine structure spectrum indicates that Ru clusters are Ru3+ species, and Ru atoms are mainly coordinated with Cl with a coordination number of 6.5. Fourier-transform infrared (FT-IR) spectra and solid-state nuclear magnetic resonance hydrogen spectra (1H NMR) indicate that the assembly process of Ru clusters is formed by noncovalent interactions, including hydrogen bonding and hydrophilic interactions. Additionally, the Ru-F127 CANs exhibit excellent photothermal conversion performance in the near-infrared (NIR) region.