High yield production of inorganic graphene-like materials (MoS₂, WS₂, BN) through liquid exfoliation testing key parameters

Abstract

Inorganic graphene-like materials such as molybdenum disulfide (MoS₂), tungsten sulfide (WS₂), and boron nitride (BN) are known to have electronic properties. When exfoliated into layers and casted onto carbon nanofilms, they can become potentially cheap and efficient electronic materials for magnetic sensing and energy storage devices. The goal of this experiment is to use a general liquid-phase method to exfoliate and optimize a number of parameters that can yield the highest concentration of layered quantities of MoS₂, WS₂, and BN. The key parameters optmized were material concentration, surfactant concentration, sonication method and duration, and centrifuge speed. Therefore, different concentrations of the three materials were mixed with different concentrations of the surfactant, sodium cholate hydrate (C₂₄H₃₉NaO₅ · xH₂O), to make suspensions. These suspensions were then sonicated and centrifuged at different durations and speeds, respectively. Absorption was measured for all of the suspensions using ultraviolet-visible spectrometer to determine what parameters yielded the highest concentration of the three materials since a high UV absorption generally equated to a high yield of the layered materials. The final optimal parameters that yielded the highest concentration of each material were: 3 mg/ml material concentration, 3 mg/ml surfactant concentration, 30-minute continuous tip sonication method, and 1-hr 500 RPM centrifugation. Droplets of these optimal suspensions were then casted onto carbon nanofilms, and transmission electron microscopy (TEM) was performed on the films to confirm the layered, flaked characteristics and the hexagonal structures of MoS₂, WS₂, and BN.