[Image above] Credit: Carolina Biological Supply Company; Flickr CC BY-NC-ND 2.0

Sometimes nature makes materials science look easy. (See: chitons, mollusks, sponges, and even penguins, among many more.)

Take, for instance, diatoms—single-celled marine algae that secrete beautifully intricate silica shells.

Diatom shells are incredibly strong despite their porous structure, which also gives them interesting photonic properties. So it’s no surprise that scientists working on a variety of different applications have tried to replicate the structure of diatom shells.


Diatom shells’ intricate structure. Credit: Picturepest; Flickr CC BY 2.0

Now researchers at the University of Manchester in the U.K. have devised a strategy that gives new use to diatom shells, using the silica shells as scaffolds for building atomic sheets of molybdenum disulfide.

Thin molybdenum disulfide is piezoelectric and has other great materials properties, making the material promising for electronic and optical applications. However, it’s hard to grow thin sheets of the material easily, quickly, and inexpensively—current methods rely on mechanical exfoliation or chemical vapor deposition.

But the Manchester researchers have figured out they can grow thin flakes of molybdenum disulfide by using diatom shells as a silica substrate.

To do so, the scientists simply mixed diatom-rich diatomaceous earth with molybdenum disulfide precursor materials (MoL4) in solution, and then dried and heated the resultant powder.

This simple process grew hexagonal flakes of crystalline molybdenum disulfide, just 1–6 atomic layers thick and about 132 nm in diameter, dotted over the surface of the silica scaffolds.

According to a C&EN article about the research, “The silica in the shells is a passive insulator material, making it an ideal scaffold for other functional materials. What’s more, the periodic arrangement of the pores helps the particles trap light and gives them a high surface area.”

Considering there are more than 100,000 species of diatoms, and that the technique could be adapted to grow other 2-D compounds beyond molybdenum disulfide, this method could be used to fabricate a vast diversity of scaffold geometries and nanocrystal morphologies and compositions—all in an easy, low-cost, and scalable process.

The authors write in the paper that the nano-and microstructure of the material is promising for catalytic applications, due to its high surface area and large number of edge sites, and for electrochemical energy storage and conversion and biosensor applications.

The paper, published in Chemistry of Materials, is “Diatom frustules as a biomineralized scaffold for the growth of molybdenum disulfide nanosheets” (DOI: 10.1021/acs.chemmater.6b01738).