Figure 1. Temperature-dependent solution stabilities of the 2D materials in water.

(a) Photographs of solutions of five 2D materials dispersed in deionized water for one month. The laser light across the solution bottles provides visual assistance because some suspended materials such as h-BN are not clearly visible. The long-term solution stabilities of (b) graphene, (c) h-BN and (d) MoS₂ sonicated at the high (60 °C) and low (30 °C) temperature and stored at high (60 °C) and low (20 °C) temperatures. In (b–d), squares and triangles denote high and low temperature sonication and solid and blank denote high and low temperature storage, respectively. In (b), two types of triangles almost overlap because of fast precipitation.