title: 1H fast MAS NMR studies of hydrogen-bonding interactions in self-assembled monolayers.
abstract: The structures formed by the adsorption of carboxyalkylphosphonic acids on metal oxides were investigated by (1)H fast magic angle spinning (MAS), heteronuclear correlation (HETCOR), and (1)H double-quantum (DQ) MAS solid-state NMR experiments. The diacids HO(2)C(CH(2))(n)PO(3)H(2) (n = 2, 3, 11, and 15) were adsorbed on TiO(2) and two types of ZrO(2) powders having average particle sizes of 20, 30, and 5 nm, respectively. Carboxyalkylphosphonic acids bind selectively via the phosphonate group, forming monolayers with pendant carboxylic acid groups. Whereas dipolar coupled P-OH protons are detected on TiO(2), there are only isolated residual P-OH groups on ZrO(2), reflecting the relative binding strengths of phosphonic acids on these two substrates. From a comparative (1)H MAS NMR study with an analogous monolayer system, HO(2)C(CH(2))(7)SH coated gold nanoparticles, the hydrogen-bonding network at the monolayer/air interface is found to be quite disordered, at least for SAMs deposited on nonplanar substrates. Whereas only hydrogen-bonded homodimers occur in the bulk diacids, hydrogen bonding between the carboxylic and phosphonic acid groups is present in multilayers of the diacids on the ZrO(2) nanopowder.
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 2K6.
authors.forename: Shane
authors.initials: S
authors.lastname: Pawsey
authors.forename: Mark
authors.initials: M
authors.lastname: McCormick
authors.forename: Susan
authors.initials: S
authors.lastname: De Paul
authors.forename: Robert
authors.initials: R
authors.lastname: Graf
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: Linda
authors.initials: L
authors.lastname: Reven
authors.forename: Hans W
authors.initials: HW
authors.lastname: Spiess