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.

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

“…37 The competitive interaction of carboxylic and phosphonic acids with metal oxide surfaces has been known from the studies dealing with structures formed by the adsorption of carboxyalkylphosphonic acids on transition metal oxide powders. 42,43,45 These studies pointed out that phosphonic acids bind selectively to metal oxides and form densely packed layers covering their surface. Phosphor compounds also bind to metal oxide surfaces more strongly than carbon compounds.…”

SALDI-MS Signal enhancement using oxidized graphitized carbon black nanoparticles

“…The signal at 13.8 ppm, which probably corresponds to carboxylic protons, was notably shifted to the low-field region. This could be attributed to the extent of hydrogen bonding between the surface-bound carboxylic groups [25,26]. The acidic properties of the carboxylic groups could also be amplified by electron delocalization over the large network of aromatic rings in the graphene structure.…”

Amphiphilic Ruthenium Sensitizer with 4,4‘-Diphosphonic Acid-2,2‘-bipyridine as Anchoring Ligand for Nanocrystalline Dye Sensitized Solar Cells

“…14 Also, self-assembling of ω-alkylphosphonic acids on a wide range of metal oxide surfaces has been of great scientific and practical interest due to the ability to form robust and compact monolayers. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Hence, it is of great interest to design and synthesize amphiphilic ruthenium sensitizers containing the phosphonic acid group for dye sensitized solar cells. In this paper we report on the synthesis and photophysical and photoelectrochemical behavior of an amphiphilic sensitizer (coded as Z-955, Figure 1) endowed with 4,4′-diphosphonic acid-2,2-bipyridine (dpbpy) as the anchoring ligand.…”