Design Rules for discovering 2D materials from 3D crystals (2016)
Undergraduates: Eleanor Brightbill, Patrick C. O'Brien Tyler W. Farnsworth, Adam H. Woomer, Kaci L. Kuntz
Faculty Advisor: Scott Warren
Department: Chemistry
Two-dimensional (2D) materials, due to the extreme change in properties that accompanies a transition from bulk to a quantum-confined state, are championed as potential components for novel technologies. The optoelectronic, magnetic, and mechanical properties of existing 2D materials have been investigated for applications such as catalysis, spintronic devices, and biological sensors. However, the current library of stable 2D materials is limited to a relatively small number of material systems, and attempts to identify novel 2D materials have found only a small subset of potential 2D material precursors. As a result, there remains a need to expand the library of 2D materials and their resulting applications. Here a rigorous, yet simple, set of criteria to identify 3D crystals that may be exfoliated into stable 2D materials is presented and applied to a database of naturally occurring layered minerals. These design rules harness two fundamental properties of crystals - Mohs hardness and melting point - to enable a rapid and effective approach to identify candidates for exfoliation. We hypothesize that, in layered systems, Mohs hardness is a predictor of inter-layer (out-of-plane) bond strength while melting point is a measure of intra-layer (in-plane) bond strength. We effectively demonstrate this concept by using liquid exfoliation to produce novel 2D materials from layered minerals that are characterized by a large melting point to Mohs hardness ratio.