Whiskey-phase exfoliation: exfoliation and printing of nanosheets using Irish whiskey

Abstract

Recent advances in the liquid-phase exfoliation (LPE) of layered materials have facilitated significant progress in the creation of functional inks. While ethanol/water blends have been shown to yield reasonable nanosheet dispersions with the potential for refinement into printable inks, the exfoliated mass is typically too low for practical use. Here, we show that Irish whiskey can be used as a dispersant for nanosheets of graphene, BN and WS2, yielding stable dispersions at reasonably high concentrations. We see some benefits compared to exfoliation in simple ethanol/water mixtures which we attribute to the presence of organic compounds in the whiskey. Size selection yields nanosheets which are relatively thin, with photoluminescence spectroscopy confirming the presence of monolayer tungsten disulfide (WS2). We also show that whiskey-dispersed nanosheets of graphene and WS2 can be printed into networks. These can be combined in heterostructures to produce thin-film transistors whose current can be modulated using ionic liquid (IL) gating. These devices show on:off ratios up to 340 and mobilities up to 1.5 × 10−3 cm2 V−1 s−1. The fact that these networks can be gated at all demonstrates the robustness of nanosheet networks against external additives while the mobility reported here should represent a performance-floor for future devices.