Widening the view on dispersant-pigment interactions in colloidal dispersions with saturation transfer difference NMR spectroscopy.

The application of Saturation Transfer Difference (STD) NMR spectroscopy for the characterization of dispersant particle interactions is introduced. STD NMR has hitherto been applied, with great success, to the characterization of ligand-protein interactions and is currently a standard tool in biomolecular NMR spectroscopy. Nevertheless, the STD NMR technique has so far not yet crossed the boundaries of the biomolecular field. Here, we demonstrate that in spite of clear differences between a protein binding site and the surface of a pigment nanoparticle, the latter can also be subjected to STD NMR analysis, allowing us to detect (screen for) binding ligands, discriminate ligand from nonligand, and obtain information on the binding epitope. The approach should be generally applicable as long as the nanoparticle is comprised of a dense network of hydrogens, implicating almost all organic molecular nanocrystals. Thus it provides a novel investigative tool for the study of dispersions that is highly complementary to existing ones.