Formation of alkane‐phosphonic acid self‐assembled monolayers on alumina: an in situ SPR study

One of the molecules which has been noted to form self-assembled monolayers on aluminium oxide is the phosphonic acid molecule. A variety of chain lengths and solvents have been discussed in state of the art literature. No global consensus about the adsorption mechanism and its limitations has been found yet. In this study, we present the continuation of previous analysis of the adsorption of n-octylphosphonic acids on chemically and morphologically optimised aluminium oxides. An ex situ analysis approach, using atomic force microscopy, X-ray photoelectron spectroscopy and Visible Ellipsometry (VISE) is presented. It can be seen that from ethanol, the molecules adsorb on the surface. This occurs in a very unstable way, creating defects at the surface. Through modeling of ellipsometry data, it is found that the oxide film itself is attacked by the acids, resulting in non homogeneous organic overlayers. It seems that, from an ex situ point of view, ethanol is not suitable for the creation of n-octylphoshonic acid monolayers. The reaction of the phosphonic acids with the aluminium hydroxyls creates local aqueous environments, which are, in combination with dissolved acids, hazardous for the oxide surface.

Section: Introductionmentioning

confidence: 66%

“…They can form a bond with the aluminium hydroxyls through an acid–base elimination condensation reaction. Different solvents are employed, being for example ethanol, water and tetrahydrofurane …”

Section: Introductionmentioning

confidence: 99%

Study of the self‐assembling of n‐octylphosphonic acid layers on aluminum oxide from ethanolic solutions

Hauffman

Hubin

Terryn

2012

“…It was reported that an anodized aluminum surface coated with fluorinated alkyl phosphonic acids showed higher contact angles for water and organic liquids in comparison with the alkylsilanes with the same alkyl groups, although the reason was not clarified . Although there are some advantages of phosphonic acids for formation of SAMs on aluminum and several studies on phosphonic acid‐based SAMs on aluminum have been carried out, the formation of SAMs has not been fully understood. Recent in situ analysis revealed island growth of phosphonic acid molecules on aluminum oxide, suggesting that a monolayer is not always formed.…”

Section: Introductionmentioning

confidence: 99%

Observation of self‐assembled layers of alkyl phosphonic acid on aluminum using low‐voltage scanning electron microscopy and AFM

Sato

Fujii

Tsuji

et al. 2013

Self-assembled alkyl phosphate layers have been formed on a flat, anodized aluminum substrate in dilute ethanol solution containing 2 wt% n-tetradecylphosphonic acid (TDP) and examined by low-voltage scanning electron microscopy as well as atomic force microscopy and X-ray photoelectron spectroscopy. Locally, multi-layered alkyl phosphate films have been formed on aluminum, being clearly observed by a low-voltage scanning electron microscope operated at less than 1 kV. Atomic force microscopy observations disclosed that bilayers of tetradecylphosphonic acid are stacked on the substrate to form multilayers. The present study revealed that the uniform self-organized monolayer is not always formed readily on an oxidized aluminum surface.

“…This demonstrates that the film is not only a simple double‐layer film. Most researches proposed the monolayer adsorption model for phosphonic acid molecules on the surface of Al and the solutions involved ethanol, water and THF . However, Hauffman et al .…”

Section: Resultsmentioning

confidence: 99%

Self‐assembling behavior of TDPA molecules on inhomogeneous surface of 2024 aluminum alloy

Nie

Liu

et al. 2013

The self-assembling behavior of 1-tetradecylphosphonic acid (TDPA) molecules on the surfaces of 2024 aluminum alloys was studied with an emphasis on the different micro-structural regions of the alloy surface, specially the alloy matrix and the two main types of intermetallic particles, as well as how the adsorption was effected by changes in water content of the self-assembly solution. Surface characterization was undertaken with contact angle measurement, scanning electron microscopy and Auger electron spectroscopy (AES). The packing density of TDPA film on the alloy surface increased with the increasing water content of the self-assembly solution. It seemed that the micro-distribution of TDPA molecules was related to copper amount and the region with a higher surface copper concentration had a lower packing density of TDPA. Some pits were formed in the acidic self-assembly solutions and the exposed surfaces of the pits can quickly adsorb TDPA molecules with compactness comparative to the matrix surface. Different adsorption models of TDPA corresponding to different water content of the self-assembly solution were suggested based on the analysis of AES depth sputtering data.