Molybdenum disulfide created with the new low-cost method. Photo: University of Texas at Austin.
Molybdenum disulfide created with the new low-cost method. Photo: University of Texas at Austin.

An international team of researchers has found a way to refine and reliably produce an unpredictable and hard-to-control material that could impact environmental conservation, energy and consumer electronics.

The material, molybdenum disulfide (MoS2), is a flexible and capable semiconductor, and holds tremendous potential for numerous applications in energy storage, water treatment, and gas, chemical and light sensing. But high costs and fabrication challenges have held back wider use.

"There are many different ways to fabricate this material, but no one has yet been able to make it in a controlled and tunable dimension in large quantities, in a low-cost, reproduceable fashion," said Donglei (Emma) Fan, an associate professor in the Cockrell School of Engineering's Walker Department of Mechanical Engineering and Texas Materials Institute at the University of Texas at Austin.

As reported in a paper in Advanced Materials, Fan and her colleagues have now developed a low-cost method for fabricating thin nanoribbons of MoS2 at a large scale. Previously, researchers have only been able to make the material in small amounts, attached at random to silicon substrates. This limited the material's use, and when attached to the substrate it became very challenging to manipulate.

MoS2 is produced by adding sulfur to a morphed 'pre-cursor' material. Splitting this process into two steps – first performing the sulfurization at a lower temperature and then upping the heat – represented one of the key innovations in making MoS2 more controllable.

This allowed the research team to create a free-standing version of MoS2 in a powder form that can be dispersed into solutions for several different applications, most notably water treatment. Yun Huang, graduate student and first author of the paper, said their new process has cut the cost of fabricating a gram of the material by 3000 times, compared to previous methods for producing MoS2 nanoribbons.

These methods were also only been able to create a microscopic amount of the material. However, the researchers were able to obtain a 'spoonful' of MoS2 nanoribbons with a single synthesis, and say there no barriers to hold back scaling up the procedure to create larger quantities of the material.

Removing the dangerous element mercury from water represents one of the most impactful uses of MoS2, Fan said. A 2016 study led by the US Geological Survey found that mercury contamination is widespread at various levels across the western US, in air, soil, sediment, plants, fish and wildlife. High levels of mercury can lead to brain and kidney damage, especially in younger people. Aside from contaminated water, humans are most exposed to mercury through eating fish, which can pile up high concentrations of the element in their bodies as they consume other organisms that have been exposed.

When added to water, the team's powder version of MoS2 becomes dispersed, allowing it to soak up mercury from the water. There are several methods for removing mercury from water already, but with these new low-cost and large-scale manufacturing capabilities, MoS2 makes for a promising alternative solution.

"This is an attractive material because it has unique properties for various applications with potential to change people's lives. Being able to make the material with controlled dimensions and in a large quantity, assemble it and integrate it with pre-made devices brings MoS2 a step closer to practical applications, not just staying in the lab," Fan said.

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