The liquid exfoliation of graphene in polar solvents

• DOI: 10.1016/j.apsusc.2021.149046
• Publication Date: 2021-01-21T23:00:04Z
• Authors: Cristian Vacacela...; Marco Guevara; Talia Tene; Luis Villamagua; Gabriela Tubon Usca; Frank Maldonado; Carlos Tapia; Antonino Cataldo; Stefano Bellucci; Lorenzo S. Caputi
• Keywords: 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 7. Clean energy; 0104 chemical sciences

Abstract Graphene is the most attractive 2D nanomaterial with interesting applications from smart coating to high frequency electronics. Its production through liquid exfoliation of graphite in suitable solvents is the most practical approach to prepare graphene dispersions. In recent years, the production of graphene through a short sonication time has attracted huge attention, trying to find a balance between the quality and cost. However, little is known about how the technical parameters (solvent type, graphite amount, sonication time, centrifugation time and centrifugation speed) affect the exfoliation process. By combining different spectroscopical (UV–vis, EDS, IR, XRD and Raman) and morphological (SEM and TEM) characterizations, statistical analysis, and ab initio simulations, we present a detailed experimental and theoretical investigation seeking to explain the liquid exfoliation of graphene in polar solvents at short sonication time (up to 7 h). In particular, we demonstrate that the short-time exfoliation process can only be optimized by dispersing graphene in dimethylformamide (DMF). Raman measurements show that edge-type defects are most noticeable when graphene is exfoliated in ethanol, which is corroborated by SEM analysis. TEM results show well-exfoliated graphene nanosheets in DMF, but depend on the centrifugation speed. Computational studies (considering one- and two-graphene layers) predict that the orientation of the molecule and the number of layers affect the final adsorption energy.