Oxinate-Aluminum(III) Nanostructure Assemblies Formed via In-situ and Ex-situ Oxination of Gold-Self-Assembled Monolayers Characterized by Electrochemical, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, and X-ray Photoelectron Spectroscopy Methods

Abstract

Oxinate-aluminum nanostructures constructed on gold-mercaptopropionic acid using 5-Amino-8-hydroxyquinoline complex of aluminum(III), Au-MPA-5A8HQ-Al(III), are prepared for the first time via in-situ and ex-situ approaches, and their physiochemical characteristics are studied by cyclic and differential pulse voltammetry, electrochemical impedance spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical signal background observed for the in-situ prepared nanostructures is large and superimposed by some faradaic effects, while, it is small, smooth, and featureless for the ex-situ prepared nanostructures. To find the source of these features, effects of several parameters (like solvent, preparation method, and linking spacer between the complex and Au surface) are studied. These features are attributed to the intercalation and physical adsorption of the free 5A8HQ molecules onto the Au-MPA-5A8HQ structure when prepared via in-situ method. Nanostructures with minimum backgrounds in their electrochemical responses could be obtained via in-situ assembling of 5A8HQ from DMF solvent onto the Au-MPA surface, and then, accumulation of Al(III) onto the 5A8HQ layer, and also via ex-situ formation of 5A8HQ:Al(III) complex in the ethanol phase first, and then, transferring the complex onto the Au-MPA surface. The equilibrium constants for the intercalation and adsorption processes are calculated for the first time based on the collected experimental surface quantities.