Differential sedimentation (DS) is a popular processing method for dispersions of 2D materials, enabling production of subpopulations with narrowed lateral size and layer thickness distributions. However, characterization and optimization of this centrifugation cascade methodology has relied on surface analysis characterization techniques with limited precision. Here, we use analytical ultracentrifugation (AUC) to characterize liquid-phase subpopulations of graphene sheets generated through DS. AUC characterization enables observation of distribution tails and evaluation of processing parameters in the DS cascade. We also demonstrate the strategy of applying an additional cycle(s) of centrifugation at the same or at reduced acceleration to the pellet at each DS cascade step, resulting in significant reduction of the dispersity of each DS cascade produced subpopulation relative to the common one-cycle methodology. Additional characterization of these narrow subpopulations using surface analysis methods, including atomic force microscopy (AFM) and scanning electron microscopy (SEM), are also described and compared with AUC-derived results.

Analysis of 2D material dispersions partitioned by differential sedimentation using analytical ultracentrifugation

ACS Spring Meeting 2021

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