Boron nitride nanomesh is a novel inorganic nanostructured two-dimensional material discovered at the University of Zurich, Switzerland in 2003. It is similar in structure to graphene, consisting of a single layer of boron and nitrogen atoms.
Unlike graphene, nanomesh is not completely planar - a lattice mismatch between the material and the substrate it is formed on result in strong interactions which create a regular mesh assembly of pores and raised areas.
The nanomesh structure has a nanometer scale feature size, with the distance between two pore centers around 3 nm. Each pore has a diameter of about 2 nm and depth of about 0.05 nm. The lower regions of the nanomesh are strongly bound to the underlying metal, while the upper regions are bound to the surface by strong cohesive forces within the layer.
Boron nitride (BN) nanomesh is stable under air, vacuum and in some liquids, and also up to temperatures of 796°C (1465°F). It has the ability to capture and hold metallic clusters and molecules within its pores, if they are of a similar size to the pore diameter.
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Boron nitride nanomesh has a highly regular structure of nanopores and ridges caused by interactions with the substrate. Image Credits: Wikipedia.
Discovery of 2-Dimensional Boron Nitride
The first mesh of 2D hexagonal boron nitride was developed in 2003 by researchers at the University of Zurich. The material had a 2 nm hole size and 3 nm periodicity on a Rh(111) single crystalline surface by self-assembly, and was inert and stable up to temperatures of 1000K.
The nanomesh was created by exposing clean rhodium surface to borazine, producing two layers of the 2D material. Hole formation in the mesh is driven by lattice mismatch of the rhodium substrate and the film. With around 400 boron and nitrogen atoms in the mesh unit cell, the mesh can be observed using scanning tunneling microscopy under process conditions.
The edges of the pores of the mesh allow stable covalent attachment of biological or organic molecules, allowing the creation of well-structured functional surfaces.
The attachment of large molecules can lead to the formation of self-assembling supramolecular structures that can be used for biotechnology applications.
In addition, metal deposited on the nanomesh produce highly monodisperse metallic nanoclusters that are vital for catalysts with high selectivity and activity.
Applications of Boron Nitride Nanomesh
Some of the applications of 2D boron nitride films include the following:
- Nanocatalysis
- Spintronics
- Optoelectronics, mainly as deep UV light emitters
- Surface functionalization for assembling biosensors, nanotransistors, etc.
- Data storage media
- Quantum computing.
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Hexagonal boron nitride has a similar structure to graphene - this makes it ideal for use as a substrate to preserve graphene's properties, for example in graphene-based dielectrics. Image Credits: Lawrence Berkely Lab
Conclusion
The recent boom in graphene research has stimulated interest in investigating other 2D nanomaterials. Boron nitride nanostructures such as nanomesh are well positioned to take advantage of this boost in interest, as hexagonal boron nitride is an isoelectric analog of graphene, so it shares some of its structural characteristics, but some properties, like the bandgap, differ greatly between the two materials.
The main type of 2D boron nitride nanostructures include nanomeshes, nanoribbons and nanosheets.
Nanomeshes are variations of nanosheets supported on certain metal substrates where interactions between the substrate and the nanosheet result in periodic shallow regions on the surface of the nanosheet.
Another set of nanostructured materials which has drawn research attention is graphene/BN hybrid materials, either with alternating layers of the two materials, or in-plane nanocomposites. The heterolayer structures in particular are interesting materials for nanoelectronics research, as they act as excellent dielectric substrates for graphene electronic devices.
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