MATERIAL FEATURES & APPLICATIONS FOR INDUSTRY
Molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are semiconducting analogs of famous graphene. Especially MoS2 is used in the industry already now, as a catalyst for oil desulfurization reaction (multi-billion industry) and as an additive in lubricants (multi-million industry). But it is also believed that thanks to the remarkable physical, chemical, optical and mechanical properties, the material will find use in future industries. Many excellent scientific groups across the globe are working to convert this vision to reality. Currently, there is a significant research interest here. Noteworthy, MoS2 can be found in nature as a relatively abundant mineral – molybdenite, which is a scalability resource.
We were the first to discover a way to significantly improve the properties of natural MoS2 by introducing perfect and highly controllable edges in the material. These edges follow the crystallographic axes of the material and thus form perfect hexagonal nanostructures. Based on this we formed a start-up company and filed a patent application. In a sense, we have invented a way to convert a standard MoS2 into a ”composite” MoS2 where useful properties of edges are combined with useful properties of planes in the same material.
- Since catalytic sites are located at the edges, our method allows us to significantly improve catalytic activity by exposing the edges. Moreover, since we create perfect edges of the right catalytically-relevant zigzag topology, we can convert nearly all surface of the material into a catalytically-useful area. The standard MoS2 is already known as a catalyst in photo/electrochemical water splitting (hydrogen evolution reaction), desulfurization of oil (removing hazardous sulfur-containing impurities), and electrochemical CO2 reduction to CH2OH. The catalytic activity of our perfect hexagonal MoS2 will significantly beat the standard one.
- The material is highly bendable, but at the same time mechanically strong. By introducing highly controllable ideal hexagonal holes, we can make the material impenetrable for large objects, like biopolymers, viruses, bacteria, microplastics, and alike (depending on the feature size, which we can control), but still penetrable for small molecules, like water, ethanol, oxygen and so on. The size of the holes we create can be accurately controlled from a few nanometers to tens of microns. These small features can be applied together with micro and nanofluidics.
- The material has extremely high (n>4 in the visible range) and anisotropic (n_o-n_e>2) optical refractive index in the visible and near-infrared spectrum. By introducing nanoscale features, we can control the color of the reflected or transmitted light across the entire visible range – from blue to red. We can also create flat optics (lenses, gratings, waveguides, resonators), so-called metasurfaces, out of our material, which can affect the nanophotonics industry.
- The zigzag edges that we create are ferromagnetic and metallic, unlike the semiconducting planes. Thus, by creating an edge-plane composite, we can affect the electronic and magneto-electronic properties of the ”mesh” material, which will be entirely different from the standard one. For example, due to inclusions of symmetry-broken edge states, the new material is expected to be piezoelectric and ferromagnetic. This will in turn allow manipulating the electronic transport properties by external electric, mechanical, and magnetic fields. Yet even the standard material is believed to play a role in future electronics as MoS2 allows creating transistors smaller than Si and MoS2 photodetectors can be made in a monolayer MoS2 form. Due to nearly atomically sharp edges, our method allows creating channel width as narrow as 3 nanometer, more than 10x better than the currently reported state of the art.
- Standard MoS2 is used as a biosensor and gas sensor (NH3, NOx, SOx), thanks to the surface chemistry properties of the exposed S-bonds. Our new material exposes not only S-bonds of the basal plane but also S-bonds and Mo-bonds at the zigzag edge. This will allow us to extend the sensitivity to other gases, in particular H2, and to significantly improve the performance of existing sensors.
- The method has a high scalability potential due to the abundance of MoS2 and the wet-etching nature of our method. The material can be prepared in large quantities in colloidal solutions, sprays, and powder forms. The natural molybdenite contains a small amount of useful impurities, typically Re, Ru, Cu, and Fe. Exposing these sites by our method will greatly enhance its application potential in terms of catalysis and sensing, at the same time allowing to keep production cost low (the natural mineral is extremely cheap raw material).