Summary: A group of researchers at the National University of Singapore has built up a technique to utilize selenium doping in creating nanocrystals, which can result readymade removable molecules. Ultimately, this innovation has produced nanostructures which are more selective and structurally precise than those prepared earlier, opening up new possibilities for on-surface synthesis techniques.
The Power of Flexing
Generally, on-surface synthesis has been studied before for conformationally rigid precursors. In contrast, conformationally flexible precursors represent uncharted territory for the NUS team that exhibits much promise for enabling the synthesis of complex functional nanomaterials.
Herein the precursor, mTBPT with three meta-bromophenyl group as ligand for HT-LnMOF. Its flexibility, two possible symmetry elements (one for each conformation) and double X-axis make this a good example. The addition of only 0.01 monolayer of selenium at temperatures ranging from room temperature to 365K doping the system was necessary for high selectivity in favoring the C3h conformer, within a range indicated by experimental results.
One benefit of this selective process was the creation of organized 2D metal-organic frameworks (MOFs), which greatly increased structural uniformity of their nanostructures. By using several advanced techniques, such as high resolution scanning tunneling microscopy and spectroscopy, and non-contact atomic force microscopy at low temperature (4K), the researchers were able to study the transformation between the different conformers induced by selenium doping.
The Selenium Advantage
Given the rejuvenated interest in on-surface synthesis and two-dimensional selenides, the results of the research team underline the necessity to consider doping effects from selenium.
Prof Andrew Wee from the Department of Physics at NUS will use insights gained from this project to work on making metal-organic and covalent organic framework nanostructures with a variety of properties in a more controllable manner.
Density functional theory calculations were applied to simulate the interconversion of Cs-Cu and C3h-Cu moieties on the Cu(111) substrate. These simulations shed light on the pronounced topology selectivity of the C3h conformers realised by selenium doping.
In doing so, the NUS team has demonstrated new opportunities in engineering selenium-based nanomaterials with well-defined structures and functionalities as a result of the inherent nature of selenium. The technique, which can be applied to produce highly ordered porous films from nanoparticles for a variety of applications, including electronics and optoelectronics28 as well as catalysis and energy storage29–31, opens up the possibility of creating new types of advanced nanomaterials.
Conclusion
While a simple practice approach of selenium doping developed by the NUS team had showcased considerable promise to realize highly selective, structurally uniform nanostructured materials. In doing so, they have unraveled new ways for structurally tailoring nanomaterials that require them to control on their morphology or microstructure by taking the flexibility of precursors into account. This new dimension in on-surface synthesis not only has key potential for future applications in electronics and energy storage, but could open pathways towards revolutionary breakthroughs within the domain of nanotechnology.
