posted on 2020-03-04, 20:14authored byMengwen Yan, Sean M. Collins, Paul A. Midgley, Jeremy I. Feldblyum
Advances in the production of two-dimensional
(2D) materials such
as graphene and MoS2 during the past two decades have spurred
the search for other van der Waals materials with distinct functional
properties. However, reducing the dimensionality of bulk van der Waals
materials can lead to structural rearrangement and chemical degradation,
especially in the presence of air. These challenges have slowed the
progress of the discovery and analysis of chemically diverse 2D materials.
Here, we provide a case study on the shear exfoliation of a class
of wide band gap van der Waals materials termed II–VI layered
hybrids (II–VI LHs) and show how reducing their dimension influences
their structural and chemical stabilities. ZnSe(butylamine) and ZnSe(octylamine)
are exfoliated, yielding shear-thinned material whose resistance toward
degradation via oxidation is studied in depth by a variety of macro-
and microscopic characterization techniques. Mechanical energy input,
solvent–ligand interaction, and exposure to ambient conditions
all play important roles in the stability of these materials. Our
findings suggest that moderately coordinating alkylamine layers stabilize
2D materials that would otherwise degrade during exfoliation and exposure
to air.