Colloidal Stability, Sedimentation, and Aggregation of Crystalline Two-Dimensional Crumpled Birnessite Flakes, Their Dye Adsorption and Immune Cell Response.

Highly crystalline two-dimensional (2D) flakes of birnessite, a polymorph of manganese oxide with a MnO chemistry, were synthesized by reacting manganese oxide, MnO, at 80 °C with aqueous solutions of tetramethylammonium hydroxide (TMAH) for tens of hours. Their colloidal stability, aggregation, and sedimentation were studied as a function of ionic strengths of Na and Li cations. After reaction, a water-based stable colloidal suspension (ζ-potential ∼ -31 ± 1 mV) was obtained.