Spectroscopic Evaluations of Interfacial Oxidative Stability of Phosphonic Nanocoatings on Magnesium

Abstract

Magnesium (Mg), and its alloys, is being investigated for its potential biomedical applications for its use as a biodegradable metal. However surface modification strategies are needed to modify the surface of the Mg alloy for its applicability in these applications. Self-assembled monolayers (SAMs) have been investigated as a coating strategy on magnesium for biomedical applications. In this report we evaluate the oxidative interfacial stability of phosphonic nanocoatings on magnesium using spectroscopic techniques. Self-assembled mono-/multilayers (SAMs) of octadecylphosphonic acid (ODPA) were formed on the native oxide layer of magnesium alloy using solution deposition technique. The SAMs modified Mg alloy and its oxidative stability were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). FTIR studies indicated mono-/bidentate bonding of the phosphonic SAMs to the Mg alloy surface. XPS confirmed SAM formation showing presence of “P” peaks while consequently showing decrease in peak intensity of Mg peaks. XPS analysis of the phosphonate peaks showed consistent presence of this peak over a period of 21 days. AFM images showed consistent coverage of the Mg alloy over a period of 21 days. The results collectively confirm that the monolayers are stable under the chosen oxidative study.

XPS and FT-IR Characterization of Selected Synthetic Corrosion Products of Zinc Expected in Neutral Environment Containing Chloride Ions

“…It was noted in own preliminary tests that the corrosion process of Zn-Fe-Mo coatings in 0.05 mol•dm −3 solution of NaCl is slow enough that the use of XRD and FT-IR techniques does not provide any information on the chemical composition of corrosion products. For this purpose, X-ray photoelectron spectroscopy (XPS) is commonly used [7]. However, the correct determination of the chemical states of the elements needs reference spectra of the expected compounds.…”

Organic corrosion inhibitors: where are we now? A review. Part IV. Passivation and the role of mono- and diphosphonates

“…The authors [68] studied the formation and stability of SAMs formed by one of the most hydrophobic phosphonate reagents, APhC 18 , as a coating on a Mg alloy (96% Mg, 3% Al, 1% Zn) for biomedical applications. A carefully cleaned alloy sample was immersed for 48 h in a solution of dimethylsulfoxide (DMSO) containing 2 mM APhC 18 , then rinsed in DMSO and ultrasonicated for 3 minutes in deionized water to remove any excess surfactant.…”

Electrografting of mixed organophosphonic monolayers for SI-ATRP of 2-methacryloyloxyethyl phosphorylcholine

“…SAMs based on organophosphonic acid derivatives are selected because they are known to robustly graft on metal oxide surfaces via M-O-P bonds which are very resistant to hydrolysis. [28][29][30][31][32] They constitute a strong reinforcement of the metal surface in aggressive environments. [33][34][35][36][37] To confer to the surface additional properties for applications, e.g., antifouling, 38,39 lubrication, 40,41 cell culture 42,43 or even cell differentiation, 44 appropriate polymer coatings are also used.…”