(13e) Analysis of 2D Material Dispersions Partitioned By Differential Sedimentation Using Analytical Ultracentrifugation

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 and MoS₂ 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 a second cycle of centrifugation at the same 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, such as layer number distributions, are also described and compared against literature reported relations for flake size and optical properties.