Two-dimensional molecular networks via on-surface reactions

The assembly of individual molecular units into molecular networks mediated by on-surface reactions is an exciting emerging paradigm for the synthesis of novel two-dimensional (2D) systems and materials. A famous recent example of such assembly is the formation of graphene nanoribbons starting from small precursor molecules adsorbed on an atomically flat gold surface, which then diffuse and subsequently react with each other to create the ribbon [1].

Concurrently, recent advances in scanning probe microscopy (most notably in non-contact atomic force microscopy) have allowed one not only to image individual molecules on atomically flat surfaces with unprecedented resolution [2], but also to identify various products of staged on-surface reactions [3] and, in this way, “visualise” the reaction.

Here we extend such principles to a novel class of molecules (borazatruxenes and congeners) to be used as molecular precursors for the assembly of 2D, graphene-inspired molecular networks: their structure, symmetry and interconnectivity can be varied allowing one to tune the assembly of different 2D networks, which can hence be made to have bespoke electronic properties controlled by the arrangement of molecules in the network. Most importantly, due to the synthetic approach, we will be able to assemble isomeric networks, whereby the same number and type of atoms are interconnected in different ways leading to new materials with new properties. Finally, the electronic properties of the assembled networks will also be investigated (field effect transistors and OLEDs with tuneable properties are just two possible outcomes of these new materials).

Moreover, we will attempt to assemble not only on metallic surfaces (which are traditionally used), but also on functional surfaces (such as insulators, graphene or other 2D materials) - if successful, this would represent an extremely powerful, highly flexible route towards the synthesis of novel stacked 2D hybrid heterostructures and multilayer systems, which will be instrumental for the design of entirely novel quantum electronic components.

The research is highly interdisciplinary, providing excellent opportunities for training at the interface between physics, chemistry, surface science, and materials science; and underpinned by the close collaboration between the two supervisors, Dr. Adelina Ilie (Lead supervisor) in the Physics Department, and Dr. Dan Pantos in the Chemistry Department. The core of the work, to be undertaken in the Physics Department, is performing atomically-resolved scanning probe microscopy (i.e. non-contact atomic force and scanning tunneling microscopies) and the associated surface science for both structural and electronic characterization of the on-surface assembled networks; while bespoke molecular precursors will be obtained (design and synthesis of precursor molecules) in collaboration with Dr. Pantos, who will also advise on the on-surface chemistry of the precursors.

The PhD student will be embedded in two cross-University research centres, the Centre for Graphene Science, the Centre for Nanoscience and Nanotechnology (CNAN), as well as in the Centre for Precursor Design of the Chemistry Department; and will also participate in the strong international collaborations on related themes of the two supervisors.

Anticipated start date: 2 October 2017.