Engineered inorganic-organic composite nanomaterials have received significant interest as tunable, platform materials for next generation sensors, (photo) catalysts, and sorbents, among other applications. For such materials with dynamic surface coatings (e.g. soft, flexible, responsive, etc.), in most cases, fundamental understanding of aqueous behavior remains outstanding. In this presentation, we will quantitatively describe the specific role of organic coating(s) for inorganic-organic nanomaterials (here as discreet particles), systematically in terms of colloidal stability for highly controlled manganese oxide (MnxOy) core materials (three sizes, one shape - spherical 14, 18, and 25 nm; termed NPs). Colloidal stability and (relative) aggregation density were correlated with (surface) ligand length and functionality, with results differing from what would be expected based on the classic Schulze-Hardy rule. Interestingly, poly(maleic anhydride-alt-1-octadecene,) coated NPs are more colloidally stable at the point of zero charge (PZC) than at pH 7 with critical coagulation concentrations (CCC) for NaCl at 334 mM and CaCl2 at 1.5 mM (pH 7), compared to CCC values of 807.2 mM in NaCl and 209.8 mM in CaCl2 at PZC (pH 2.5) Overall, the change in polymer conformation (shrinkage), as a function of pH and ionic strength, dramatically increases colloidal stability, although NPs effectively lose surface charge – thus implicating the role of steric stabilization. Lastly, polymer conformation dynamics as a function of water chemistry are quantified using quartz crystal microbalance with dissipation monitoring.

Quantifying nanoparticle stability and aggregation dynamics as a function of organic coating structure and density

254th National Meeting (2017)

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