Different paths take 2D material to different places

Physicists at the University of Bath in the UK have developed a flexible process for synthesizing a wide range of novel nanomaterials with various morphologies, which have potential applications in areas such as optics and sensors. The physicists report their work in a paper in ACS Nano.

The nanomaterials are formed from tungsten disulphide –a type of transition metal dichalcogenide (TMD) – and can be grown on insulating planar substrates without requiring a catalyst. TMDs are layered materials, and in their two-dimensional form can be considered the inorganic analogues of graphene.

The physicists synthesized various tungsten disulphide morphologies, including two-dimensional sheets growing parallel to the substrate, nanotubes and a nanomesh resembling a 'field of blades' growing outwards from the substrate. These morphologies were all possible thanks to the PhD research of Zichen Liu at the University of Bath, in which he experimented with splitting the growth process into two distinct stages. Through this decoupling, the growth process could be routed down different paths, allowing it to be guided to produce all the different morphologies.

So far, the 'field of blades' morphology has shown powerful optical properties, including strong non-linear effects such as second harmonic generation. This involves doubling the frequency and halving the wavelength of laser light, changing its color as it does so. The strength of these effects opens up a range of optical applications for the material.

"The simplicity of this process is important from the standpoint that it allows us to obtain practically all phases of this transition metal dichalcogenide, from in-plane to out-of-plane, as well as from two-dimensional sheets to one-dimensional nanotubes and everything between," said Adelina Ilie from the University of Bath's Department of Physics, who led the research. "Usually different processes are used to create the two-dimensional or the one-dimensional morphologies. Our process, instead, leads to tunable materials with tunable properties.

"The 'field of blades' morphology is entirely new, and due to its very large effective surface area, might be of interest not only for the non-linear optical properties we showed so far, but also for application in various sensing technologies. We are exploring all these avenues now."

"We haven't actually been able to test the upper limits of the optical effects yet because the signal is too strong for the equipment we used to probe it," added Ventsislav Valev, also from the University of Bath's Department of Physics, who tested the nanomesh for optical properties. "We are talking about a material that is one or two atoms in thickness; it is quite extraordinary. Its arrangement into a 'field of blades' clearly increases the signal."

The team plans to continue exploring the properties of these novel nanomaterials.

This story is adapted from material from the University of Bath, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.