Periodic Reporting for period 4 - Mol-2D (Molecule-induced control over 2D Materials)
Berichtszeitraum: 2023-04-01 bis 2024-03-31
Materials formed by atomic thin layers constitute a common topic of interest in physics, chemistry and materials science, with van der Waals (vdW) heterostructures playing a central role as they offer the opportunity to study fundamental physical phenomena, while developing applied research towards the design of novel materials and devices. In Mol-2D a molecular approach to 2D materials is developed, which aims at designing metal-organic 2D magnets and fabricating magnetic heterostructures showing emergent properties. In particular, a new class of heterostructures is created by combining functional magnetic molecules with 2D materials with the aim of tuning/improving the properties of the “all surface” 2D material through the interactions established with the molecular system. As molecules, we concentrate on bistable spin crossover complexes able to switch between two spin states upon the application of external stimuli (temperature, light, pressure, electrical field, etc.). The driving idea is that of tuning the properties of the 2D material via an active control of the hybrid interface. As distinguished from a conventional chemical functionalization, our approach makes a strong effort to prepare high-quality molecular/2D heterostructures suitable in nano/microelectronics.
This approach has provided an entire new class of 2D molecule-based magnets and smart heterostructures of direct application in highly topical fields like electronics, spintronics or energy storage. We have pioneered on the one hand the design of chemically stable metal-organic layered magnets, which can be exfoliated and characterized down to the monolayer, while tuning their structures and magnetic properties by varying their chemical composition. On the other hand, an exquisite control over the properties of a 2D material has been achieved by fabricating twisted magnetic heterostructures exhibiting tunable magneto-transport properties, or by combining stimuli-responsive spin crossover (SCO) molecules with graphene and other 2D materials to obtain smart devices whose properties can be tuned by applying an external stimulus. This has allowed us to prepare for the first time twisted magnetic bilayers affording ultrathin spin valve devices, robust electronic devices based on spin crossover/2D heterostructures, and energy storage devices based on magnetic/graphene nanocomposites showing a giant enhancement of the capacitance when a small magnetic field is applied.
This approach has provided an entire new class of 2D molecule-based magnets and smart heterostructures of direct application in highly topical fields like electronics, spintronics or energy storage. We have pioneered on the one hand the design of chemically stable metal-organic layered magnets, which can be exfoliated and characterized down to the monolayer, while tuning their structures and magnetic properties by varying their chemical composition. On the other hand, an exquisite control over the properties of a 2D material has been achieved by fabricating twisted magnetic heterostructures exhibiting tunable magneto-transport properties, or by combining stimuli-responsive spin crossover (SCO) molecules with graphene and other 2D materials to obtain smart devices whose properties can be tuned by applying an external stimulus. This has allowed us to prepare for the first time twisted magnetic bilayers affording ultrathin spin valve devices, robust electronic devices based on spin crossover/2D heterostructures, and energy storage devices based on magnetic/graphene nanocomposites showing a giant enhancement of the capacitance when a small magnetic field is applied.
The work performed in Mol-2D can be grouped around 3 classes of materials / heterostructures: I) inorganic 2D superconductors and magnets; II) molecule-based 2D magnets and hybrid molecular/2D heterostructures; III) 2D composite materials. The main achievements are:
For I, the magnetic characterization of the family of 2D antiferromagnets MPS3 (M= Mn, Fe, Ni) using nanomechanical resonators (this technique is used for the first time to probe magnetic transitions in membranes based on 2D magnets), and the preparation of novel vdW heterostructures and electronic devices incorporating quantum spin liquids (1T-TaS2), 2D superconductors (NbSe2) and 2D magnets (CrSBr) in the 2D limit. Emergent properties are observed in these vdW heterostructures. In particular, we note the hysteretic multistep magneto-transport behavior observed in orthogonally-twisted monolayers of the CrSBr magnet, a groundbreaking result of interest to fabricate ultrathin vdW spintronic devices with tunable properties.
For II, the isolation of magnetic monolayers based on metal-organic frameworks (MOFs) showing superior stability and a chemical control over the magnetic properties as compared with the inorganic analogs, and of smart molecular/2D heterostructures by interfacing SCO compounds of different dimensionalities — sublimable molecules, nanoparticles and 2D MOFs —¬ over graphene and other 2D materials. This approach has provided the first examples of robust electronic devices in which the spin transition can be sensed electrically and optically.
For III, the preparation of magnetic nanoparticles/graphene nanocomposites exhibiting a giant enhancement of the electrochemical capacitance induced by magnetic fields or electron beams, and the development of a novel synthetic approach to prepare in large amounts (Kg scale) electroactive layered metal hydroxides.
These results have been widely disseminated as invited talks in the prime scientific conferences devoted to molecular magnetism and spintronics, coordination chemistry and graphene, and published in high-impact journals of chemistry, physics and materials science. Results related to 2D nanocomposites have been patented and exploited to develop high-performance hybrid supercapacitors and robust electrocatalysts for green hydrogen production. In this last case a spin-off company was created in November 2021 (2D-Match gave rise in November 2023 to the R&D company MATTECO).
For I, the magnetic characterization of the family of 2D antiferromagnets MPS3 (M= Mn, Fe, Ni) using nanomechanical resonators (this technique is used for the first time to probe magnetic transitions in membranes based on 2D magnets), and the preparation of novel vdW heterostructures and electronic devices incorporating quantum spin liquids (1T-TaS2), 2D superconductors (NbSe2) and 2D magnets (CrSBr) in the 2D limit. Emergent properties are observed in these vdW heterostructures. In particular, we note the hysteretic multistep magneto-transport behavior observed in orthogonally-twisted monolayers of the CrSBr magnet, a groundbreaking result of interest to fabricate ultrathin vdW spintronic devices with tunable properties.
For II, the isolation of magnetic monolayers based on metal-organic frameworks (MOFs) showing superior stability and a chemical control over the magnetic properties as compared with the inorganic analogs, and of smart molecular/2D heterostructures by interfacing SCO compounds of different dimensionalities — sublimable molecules, nanoparticles and 2D MOFs —¬ over graphene and other 2D materials. This approach has provided the first examples of robust electronic devices in which the spin transition can be sensed electrically and optically.
For III, the preparation of magnetic nanoparticles/graphene nanocomposites exhibiting a giant enhancement of the electrochemical capacitance induced by magnetic fields or electron beams, and the development of a novel synthetic approach to prepare in large amounts (Kg scale) electroactive layered metal hydroxides.
These results have been widely disseminated as invited talks in the prime scientific conferences devoted to molecular magnetism and spintronics, coordination chemistry and graphene, and published in high-impact journals of chemistry, physics and materials science. Results related to 2D nanocomposites have been patented and exploited to develop high-performance hybrid supercapacitors and robust electrocatalysts for green hydrogen production. In this last case a spin-off company was created in November 2021 (2D-Match gave rise in November 2023 to the R&D company MATTECO).
Most of the results obtained in Mol-2D are beyond the current state-of-the-art. Just to mention a few, we can consider: i) magnetic characterization of 2D inorganic antiferromagnets, as well as molecular-based 2D magnets, using micromechanical resonators; ii) the magnetic, electrical and optical characterization of the semiconducting magnet CrSBr in the monolayer limit; iii) the investigation of spin-twistronics beyond moiré, with the exploitation of the magnetic anisotropy of CrSBr to prepare twisted spin valves exhibiting emergent and tunable properties. iv) isolation of monolayers of molecular-based magnets and magnetic characterization of thin layers of these antiferromagnets using micromechanical resonators; v) design of smart molecular/2D heterostructures using both a chemical approach and a deterministic physical positioning of the two components; vi) the exploitation of molecular/2D heterostructures based on spin crossover molecules to prepare robust electronic devices in which the spin switching can be thermally or optically triggered and readout via electrical or optical measurements; vii) the preparation of 2D magnetic nanocomposites that respond to a magnetic stimulus to significantly enhance their supercapacitive properties; viii) the integration of these 2D magnetic nanocomposites in hybrid supercapacitors with the final aim of reaching better performances than those obtained in the current hybrid devices; ix) the preparation in large amounts of very efficient electrocatalysts for water splitting based on layered metal hydroxides.