Structural studies of zirconium alkylphosphonate monolayers and multilayer assemblies

Abstract

Zirconium organophosphonates form thermally stable surface multilayers of predictable ellipsometric thickness. Fluorescence and nonlinear optical properties of dyes incorporated in such films indicate organized structures; however, other data place limits on the degree of order obtained. Here, we present evidence gleaned from IR, XPS, and cyclic voltammetry that Zr phosphonate multilayers are less perfect than previously thought and contain defects arising in the initial stages of film growth. We still consider the transition metal phosphonate matrix to be attractive for constructing novel optical materials, but in fabricating active structures it will be necessary to compensate for defects. Approaches to doing so are under evaluation.

Dynamics within a Single Molecular Layer. Aggregation, Relaxation, and the Absence of Motion

“…There is evidence in the literature that the packing density of the organic portions of the ZP structures is mediated by the lateral spacing of the inorganic interlayer linking functionalities. 13, 53,54 The ZP lattice has been shown to cause disorder in layers because the spacing it enforces is larger than the molecular area of most organic moieties. 9,55 This means that the spacing between individual chromophores may be larger than the intermolecular distance that is optimum for aggregate formation, so that, even if the chromophores are deposited onto the surface as pairs, they are likely to separate over time, giving rise to the spectral "annealing" we observe.…”

Strategies for the growth of self-assembled phospholipid adlayers

“…We expect that DMPA will form a strong complex with Zr 4+ based on a wealth of literature covering the formation of Zrphosphates and phosphonates [3,[12][13][14][15][16][17][18][19][20][21][22][23][25][26][27][28][29]31,[34][35][36][37][38]. For the other phospholipid head groups, intuition suggests that steric considerations would preclude the efficient formation of a ZP complex with a phospholipid.…”

DNA-Functionalized MFe2O4 (M = Fe, Co, or Mn) Nanoparticles and Their Hybridization to DNA-Functionalized Surfaces

“…Particles treated with only tetradecanephosphonate, and presumably bearing alkylphosphonates in an outer surfactant layer, can form loose suspensions in deionized water that settle out within minutes, while untreated particles do not break apart from a dried assembly upon exposure to water. From this observation, it appears that phosphonate groups on the outer surface are conferring some hydrophilicity, but such groups are known to stick together 23 when mediated by transition metal ions, and this hydrophilicity is likely to be affected by salt concentration and pH, so it is not surprising that alkylphosphonates alone do not result in a stable aqueous colloid. This suggests the strategy of replacing the outer phosphonates with a different surfactant.…”