On May 4th, 2020, Prof. Shern-Long Lee’s group published a new paper in Nanoscale (JCR 1, if=6.97). The title of the work is named Nanoscale Tailoring of Supramolecular Crystals via an Oriented External Electric Field. The research was finished by Xingming Zeng, Sadaf Bashir Khan, Ayyaz Mahmood, and Shern-Long LEE*.

The abstract for this publication is as follows: 

The orientated external electric field of scanning tunneling microscope (STM) has recently been adapted for controlling the chemical reaction and supramolecular phase transition at surfaces with molecular precision. However, to date, advance controls using such electric-fields for crystal engineering have not been achieved yet. Here, we present how the directional electric-field of STM can be utilized to harness supramolecular crystallization on a solid surface. We show that a glass-like random-tiling assembly comprised of p-terphenyl-3,5,3’,5’-tetracarboxylic acid can transform to close-packed periodic assemblies under positive substrate bias conditions at the liquid/solid interface. Importantly, the nucleation and subsequent crystal growth for such field-induced products can be artificially tailored at the early stage in a real-time fashion. Through this method, we were able to produce a two-dimensional supramolecular single crystal. The as-prepared crystals with apparent brightness are ascribed to a spectroscopic feature linked to the electron density of states, which is thus strongly STM bias dependent.

Paper Link: https://pubs.rsc.org/en/content/articlelanding/2020/nr/d0nr01946a#!divAbstract

Fig 1. A scheme to show our method for preparing single crystal from selective nucleation and subsequent tailored growth of TPTC via STM.

Fig 2. The consecutive images showing the dynamics of the formation of a supramolecular single crystal.

Fig 3. The consecutive images of STM revealing the re-assembly dynamics of the self-repairing in the inner structure of the close-packing.