Using Interaction of Nano Dipoles to Control the Growth of Nanorods

Breaking Radial Dipole Symmetry in Planar Macrocycles Modulates Edge-to-Edge Packing and Disrupts Cofacial Stacking

Dipolar interactions are ever-present in supramolecular architectures, though their impact is typically revealed by making dipoles stronger. While it is also possible to assess the role of dipoles by altering their orientations by using synthetic design, doing so without altering the molecular shape is not straightforward. We have now done this by flipping one triazole unit in a rigid macrocycle, tricarb. The macrocycle is composed of three carbazoles (2 Debye) and three triazoles (5 Debye) defining an array of dipoles aligned radially but organized alternately in and out. These dipoles are believed to dictate edge-to-edge tiling and face-to-face stacking. We modified our synthesis to prepare isosteric macrocycles with the orientation of one triazole dipole rotated 40°. The new dipole orientation guides edge-to-edge contacts to reorder the stability of two surface-bound 2D polymorphs. The impact on dipole-enhanced π stacking, however, was unexpected. Our stacking model identified an unchanged set of short-range (3.4 Å) anti-parallel dipole contacts. Despite this situation, the reduction in self-association was attributed to long-range (~6.4 Å) dipolar repulsions between π-stacked macrocycles. This work highlights our ability to control the build-up and symmetry of macrocyclic skeletons by synthetic design, and the work needed to further our understanding of how dipoles control self-assembly.

Halide Ions Regulating the Morphologies of PbS and Au@PbS Core-Shell Nanocrystals: Synthesis, Self-Assembly, and Electrical Transport Properties

The geometry and surface state of nanocrystals (NCs) strongly affect their physiochemical properties, self-assembly behaviors, and potential applications, but there is still a lack of a facile method to regulate the exposed facets of the NCs, especially metal@semiconductor core-shell NCs. Herein, we present a reproducible approach for tuning the morphology of PbS NCs from nanocubes to nano-octahedrons by introducing lead halides as precursors. Excitingly, the method can be easily extended to the synthesis of metal@PbS core-shell NCs with single-crystalline shells and specific exposed facets. In addition, the halide passivation layers on the NCs are found to greatly improve their antioxidant ability. Therefore, the Cl-passivated NCs can self-assemble into atomic-coupled monolayer films via oriented attachment under ambient conditions, which exhibit enhanced electrical conductivities compared with uncoupled counterparts. The precise synthesis of nanocrystals with tunable shapes and the construction of self-assembled films provide a way to expand their application in high-performance optoelectronic devices.

Symmetry driven: the synthesis of co-substituent octasilsesquioxanes

Cubic octasilsesquioxanes with mixed substituents were directly synthesized through a sol–gel process using the mixture of i-butyl(triethoxysilane) and other alkoxysilanes.