Final Report Summary - NANOMESH (Boron Nitride Nanomesh as a Scaffold for Nanocatalysts, Nanomagnets and Functional Surfaces)
Researchers have long been trying to develop self-assembly in nanostructures for use in science and high-tech applications. A new material, called nanomesh, has an extremely tiny honeycomb pattern (each whole being at 2 nm), forming a strong coating that can be used in applications such as spintronics, nanocatalysis, quantum computing and data storage.
The main objectives of the 'Boron nitride nanomesh as a scaffold for nanocatalysts, nanomagnets and functional surfaces' (Nanomesh) project were to understand the self-assembly processes leading to this highly interesting and non-trivial nanostructure, to find routes for controlling the mesh parameters and for mass production, and to demonstrate its prospects for future applications as a sturdy oxygen- and carbon-free template for the production of nanocatalysts, nanomagnets and functionalized surfaces. Rather than taking a broad approach on self-assembly in general, the Nanomesh project thus focused on this particular h-BN material. It brought together leading specialists in Europe with unique expertise in synthetic chemistry as well as novel experimental and theoretical techniques to investigate the processes leading to the self-assembly of the nanomesh in situ, and to explore new combinations of chemical precursors and substrates in order to control the mesh size and shape. It also included the expertise for fabricating self-assembling hydrogen-bonded molecular networks in order to try to achieve higher hierarchies of self-assembly on top of the nanomesh, leading to regular structures that bridge the nanoscopic and the mesoscopic scale, and to demonstrate the design of functionalised surfaces for sensing and biological applications. An industrial partner has investigated the nanomeshes as potential substrates for electronic devices, specifically for spintronic and quantum computing applications.
The Nanomesh consortium consisted of nine partners (eight academic and one industrial) from four EU Member States and one Associated Country. The project provided the critical mass of resources and the required synthetic, experimental and theoretical expertise by including following leading universities and laboratories.
The key scientific issues of the project were efficiently tackled in three work packages. Specifically, the self-assembly processes of the h-BN nanomesh were studied in situ using complementary analytical and theoretical techniques. In parallel, new paths to nanomesh synthesis were be explored, using various alternative precursors and substrates, including low-cost metallic thin films. In parallel, promising applications of the nanomesh were evaluated and partly demonstrated, centred around nanocatalysis and nanomagnetism, as well as functional surfaces. The size of the mesh units, as well as its ruggedness, make the nanomesh a prime candidate for a self-assembling scaffold material for future nanotechnologies. For this reason most of the consortium partners will continue working with this template surface also beyond the end of the project period with alternative funding.
The objectives of Nanomesh were addressed in a multi-disciplinary way, using state-of-the-art chemical synthesis methods for new high-purity boron nitride precursors and a variety of organic molecules for nanomesh functionalisation, highly optimised molecular-beam epitaxy (MBE) and pulsed-laser deposition (PLD) methods for thin film growth of various transition metal substrates, a wide variety of novel and standard surface science and materials science techniques, such as scanning tunnelling microscopy (STM) (including a very fast high temperature version), X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle-resolved photoemission (ARPES), surface X-ray diffraction (SXRD), low-energy electron diffraction (LEED) including also spot-profile analysis (SPA-LEED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and finally very powerful theoretical tools such as density functional theory (DFT) and molecular dynamics simulations.
At the end of this three-year project (that had been granted a cost-neutral extension of three months) one can look back on a manifold of scientific results that provide a clear understanding of the nanomesh structure and a good understanding of the precursor decay and self-assembly mechanisms. Alternative precursors and substrates that could in principle be used for large-scale production of nanomesh films have been identified and successfully tested. The trapping functionality of the nanomesh pores for organic molecules to form vast molecular arrays has been fully established and is understood, while the functionality as a periodic template for the nucleation of monodisperse metallic clusters for catalytic or magnetic applications is less evident and needs more work. In the following paragraphs a few highlights of the project are briefly summarized.
At the outset of the project, it was believed that the structure of the h-BN nanomesh on Rh(111) consists of an atomic bilayer. After the first year we reported that alternative structures were being considered, one of which consisted of a single, buckled h-BN monolayer. Detailed theoretical work and further experiments have definitely settled the issue in favour of the latter structure.
Unfortunately, attempts towards direct nanomesh-based electronic device applications by the industrial partner have been unfruitful. No viable concept for transferring the mesh periodicity to a semiconductor substrate could be found. The main problem arises due to the fairly thick Rh layer needed to grow the nanomesh, which is incompatible with any established device technology. Nevertheless, the extraordinary stability of the nanomesh in application-friendly environments (ambient, water, organic solvents) that was demonstrated in this project has generated interest in other application sectors not anticipated at the beginning of the proposal. Funding is currently sought for investigating the formation of ordered molecular arrays, and functional surfaces resulting from them, by simple dip coating techniques or through electrochemical means. Last but not least, boron nitride monolayers, and in particular the nanomesh, may become an important functional element in graphene-based technologies, as insulating layers of ultimate thinness and atomic definition, due to near-perfect lattice match and related bonding properties.
Dissemination and use
The dissemination of the results from the Nanomesh project has been continuously stepped up over the project period. Numerous presentations have been given at various national and international conferences, either as invited talks, contributed talks or posters, and a number of scientific papers have been published in or submitted to international peer-reviewed journals. The nanomesh as a highly interesting template surface has become well known within the nanoscience and surface science communities through this project. Further research involving the nanomesh will be pursued by some partners and by other international research groups, therefore the dissemination of the Nanomesh results will continue in the future. Finally, a 'nanomesh' entry has been made in Wikipedia in order to share the knowledge also with the general public.
The main objectives of the 'Boron nitride nanomesh as a scaffold for nanocatalysts, nanomagnets and functional surfaces' (Nanomesh) project were to understand the self-assembly processes leading to this highly interesting and non-trivial nanostructure, to find routes for controlling the mesh parameters and for mass production, and to demonstrate its prospects for future applications as a sturdy oxygen- and carbon-free template for the production of nanocatalysts, nanomagnets and functionalized surfaces. Rather than taking a broad approach on self-assembly in general, the Nanomesh project thus focused on this particular h-BN material. It brought together leading specialists in Europe with unique expertise in synthetic chemistry as well as novel experimental and theoretical techniques to investigate the processes leading to the self-assembly of the nanomesh in situ, and to explore new combinations of chemical precursors and substrates in order to control the mesh size and shape. It also included the expertise for fabricating self-assembling hydrogen-bonded molecular networks in order to try to achieve higher hierarchies of self-assembly on top of the nanomesh, leading to regular structures that bridge the nanoscopic and the mesoscopic scale, and to demonstrate the design of functionalised surfaces for sensing and biological applications. An industrial partner has investigated the nanomeshes as potential substrates for electronic devices, specifically for spintronic and quantum computing applications.
The Nanomesh consortium consisted of nine partners (eight academic and one industrial) from four EU Member States and one Associated Country. The project provided the critical mass of resources and the required synthetic, experimental and theoretical expertise by including following leading universities and laboratories.
The key scientific issues of the project were efficiently tackled in three work packages. Specifically, the self-assembly processes of the h-BN nanomesh were studied in situ using complementary analytical and theoretical techniques. In parallel, new paths to nanomesh synthesis were be explored, using various alternative precursors and substrates, including low-cost metallic thin films. In parallel, promising applications of the nanomesh were evaluated and partly demonstrated, centred around nanocatalysis and nanomagnetism, as well as functional surfaces. The size of the mesh units, as well as its ruggedness, make the nanomesh a prime candidate for a self-assembling scaffold material for future nanotechnologies. For this reason most of the consortium partners will continue working with this template surface also beyond the end of the project period with alternative funding.
The objectives of Nanomesh were addressed in a multi-disciplinary way, using state-of-the-art chemical synthesis methods for new high-purity boron nitride precursors and a variety of organic molecules for nanomesh functionalisation, highly optimised molecular-beam epitaxy (MBE) and pulsed-laser deposition (PLD) methods for thin film growth of various transition metal substrates, a wide variety of novel and standard surface science and materials science techniques, such as scanning tunnelling microscopy (STM) (including a very fast high temperature version), X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle-resolved photoemission (ARPES), surface X-ray diffraction (SXRD), low-energy electron diffraction (LEED) including also spot-profile analysis (SPA-LEED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and finally very powerful theoretical tools such as density functional theory (DFT) and molecular dynamics simulations.
At the end of this three-year project (that had been granted a cost-neutral extension of three months) one can look back on a manifold of scientific results that provide a clear understanding of the nanomesh structure and a good understanding of the precursor decay and self-assembly mechanisms. Alternative precursors and substrates that could in principle be used for large-scale production of nanomesh films have been identified and successfully tested. The trapping functionality of the nanomesh pores for organic molecules to form vast molecular arrays has been fully established and is understood, while the functionality as a periodic template for the nucleation of monodisperse metallic clusters for catalytic or magnetic applications is less evident and needs more work. In the following paragraphs a few highlights of the project are briefly summarized.
At the outset of the project, it was believed that the structure of the h-BN nanomesh on Rh(111) consists of an atomic bilayer. After the first year we reported that alternative structures were being considered, one of which consisted of a single, buckled h-BN monolayer. Detailed theoretical work and further experiments have definitely settled the issue in favour of the latter structure.
Unfortunately, attempts towards direct nanomesh-based electronic device applications by the industrial partner have been unfruitful. No viable concept for transferring the mesh periodicity to a semiconductor substrate could be found. The main problem arises due to the fairly thick Rh layer needed to grow the nanomesh, which is incompatible with any established device technology. Nevertheless, the extraordinary stability of the nanomesh in application-friendly environments (ambient, water, organic solvents) that was demonstrated in this project has generated interest in other application sectors not anticipated at the beginning of the proposal. Funding is currently sought for investigating the formation of ordered molecular arrays, and functional surfaces resulting from them, by simple dip coating techniques or through electrochemical means. Last but not least, boron nitride monolayers, and in particular the nanomesh, may become an important functional element in graphene-based technologies, as insulating layers of ultimate thinness and atomic definition, due to near-perfect lattice match and related bonding properties.
Dissemination and use
The dissemination of the results from the Nanomesh project has been continuously stepped up over the project period. Numerous presentations have been given at various national and international conferences, either as invited talks, contributed talks or posters, and a number of scientific papers have been published in or submitted to international peer-reviewed journals. The nanomesh as a highly interesting template surface has become well known within the nanoscience and surface science communities through this project. Further research involving the nanomesh will be pursued by some partners and by other international research groups, therefore the dissemination of the Nanomesh results will continue in the future. Finally, a 'nanomesh' entry has been made in Wikipedia in order to share the knowledge also with the general public.
