We use 1H and 31P solution nuclear magnetic resonance spectroscopy to analyze the binding of phosphonic acid ligands to wurtzite CdSe quantum dots (CdSe QDs). CdSe QDs synthesized with phosphonic acids as a surfactant have a ligand shell composed of phosphonic acid and phosphonic acid anhydride moieties. Titrations of as-synthesized QDs with excess oleic acid do not induce desorption of phosphonic species, whereas titration of oleic-acid-exchanged QDs with excess phosphonic acid shows that the latter quantitatively replaces the oleic acid with a 1:1 stoichiometry. Both the stoichiometry of the oleic acid/phosponic acid exchange interaction and the ratio between the Cd surface excess and the ligand density indicate that phosponic acids bind as hydrogen phosphonates to the CdSe surface.

Interactions between phenol and cationic cetyltrimethylammonium bromide (CTAB) micelles have been investigated by means of nuclear magnetic resonance spectroscopy. The combined use of 1 H and NOESY techniques revealed that phenol has different preferred locations of interaction depending on the pH. At neutral pH (6.70) conditions, phenol molecules are preferentially located in the outer micelle region, at the micelle-water interface, while at more basic pH (9.94), the deprotonated phenol molecules (C 6 H 5 O -) are immersed into the palisade layer of the micelle. In addition, quantitative estimates of the solubilized fraction of phenol were obtained by using PFG-NMR. The results indicate that the phenol-CTAB interactions, although already present in neutral pH conditions, are largely favored in basic conditions as a consequence of the strong electrostatic interaction between the negatively charged phenolate ions and the positive charge of the cationic surfactant head group.(e)

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.

Binding of the SDS to the polymer via two mechanisms - monomeric anti-cooperative and micellar cooperative - leads to surfactant-concentration-specific macroscopic changes in the viscosity. Binding of the surfactant to the polymer drives a conformational rearrangement, and an associated redistribution of the polymer end-groups and linker associations throughout the hydrophobic domains. The composition and size of these domains are sensitive to the polymer architecture. Therefore, there is a complex balance between polymer molecular weight, ethylene oxide block size, and number of urethane linkers, coupled with the size of the hydrophobic end-groups. In particular, the urethane linkers are shown to play a hitherto largely neglected but important role in driving the polymer association.