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Electrically Tunable Functional Lanthanide Nanoarchitectures on Surfaces

Periodic Reporting for period 1 - ELECNANO (Electrically Tunable Functional Lanthanide Nanoarchitectures on Surfaces)

Reporting period: 2018-09-01 to 2020-02-29

Lanthanide metals are ubiquitous nowadays, finding use in luminescent materials, optical amplifiers and waveguides, lasers, photovoltaics, rechargeable batteries, catalysts, alloys, magnets, bio-probes, and therapeutic agents. In addition, they bear potential for high temperature superconductivity, magnetic refrigeration, molecular magnetic storage, spintronics and quantum information.

Surprisingly, the study of lanthanide physico-chemical properties on surfaces is at its infancy, particularly at the nanoscale. To address this extraordinary scientific opportunity, we will research the foundations and prospects of lanthanide elements to design functional nanoarchitectures on surfaces and we will study their inherent physico-chemical phenomena in distinct coordination environments, targeting novel approaches for sensing, nanomagnetism and electroluminescence. Importantly, our studies will encompass both metal substrates and decoupling surfaces including ultra-thin film insulators and graphene. Nurturing from these studies and in parallel, we will focus on graphene voltage back-gated supports (devices), thus surpassing the seminal knowledge on electrically-inert substrates and enhancing the scope of our research to address the overarching objective of the proposal, i.e. the design of electrically tunable functional lanthanide nanomaterials.
In order to study the properties and functionalities of lanthanides at the nanoscale, the project focuses on the design and study of three distinct nanomaterials embedding lanthanide elements: metal-organic networks, metalated porphyrinoids and molecular species containing rare-earths.
To this aim, we rely on a powerful instrumentation based on surface science techniques. First, we have designed and deployed a state-of-the-art low-temperature nc-AFM-STM.

In parallel, we have started Work Package 1 (lanthanide directed metal-organic networks), the core of the project, targeting the development of unique lanthanide metal-organic networks both on metals and on sp2-materials (graphene). We have shown that it is feasible to design such arrays on graphene, not only on metals. In addition, we have discovered that it is possible to tune the magnetic anisotropy of lanthanides by coordination with ligands, of paramount importance for one core goal of the project, the use of such elements as single atom magnets. Furthermore, under some coordination and ligand size, the lanthanides can interact with each other forming bands and thus anticipating fascinating avenues for topological non-trival materials based on lanthanides, a highly unexpected result, but of timely relevance and highly importance. Related with this discovery, we have also found that surface-supported 2D metal-organic networks based on 3d metals can be highly conductive, which is of crucial importance for ferromagnetism and topological band theory. Thus, we envision fascinating discoveries following the development of Work Package 1.

Work Package 2 (metalated porphyrinoids) is also started, though there are two major deviations from our plans. First, it is unfeasible to sublimate many expanded porphyrins and it is also quite difficult to tune the synthesis to make them sublimable, which is limiting our playground of experiments. Second, the metalation of regular macrocyclic species is not working as expected, since the lanthanide is being buried beneath the macrocycle, instead of being exposed to the vacuum. Nevertheless, progress into the properties of such systems are being made, revealing the capabilities of lanthanides to induce unpaired spins in porphyrins. In addition, a new homocoupling reaction on surfaces has been discovered, which has allowed us to synthesize unique pi-conjugated nanomaterials.
In summary, the project is being developed satisfactorily, producing relevant science and even opening totally unexpected lines of research such as topological non-trivial materials and pi-conjugated polymers.
The culmination of ELECNANO project will provide strategies for:

1.-Design of functional nanomaterials on high-technological supports.
2.-Development of advanced coordination chemistry on surfaces.
3.-Rationale of the physico-chemical properties of lanthanide-coordination environments.
4.-Engineering of lanthanide nanoarchitectures for ultimate sensing, nanomagnetism and electroluminescence.
5.-Atomistic insights of electrically tunable materials and unprecedented fundamental studies of charged-molecule/metal physics on devices.

This ERC project will be in the vanguard of knowledge of physics and chemistry, and will be skippered by our expertise of complex surface characterization with scanning probe microscopies and spectroscopy. The funding of this project would consolidate us as leading pioneers in the innovative field of lanthanides at the nanoscale.
Kepler tessellation of Au(111) by dysprosium-directed carbonitrile networks