Nanostructure Molecular Assemblies Constructed Based on Ex-Situ and In-Situ Layer-by-Layer Ferrioxamation Characterized by Electrochemical and Scanning Tunneling Microscopy Methods

Abstract

Nanostructure assemblies based on ferrioxamation of gold-mercaptopropionic acid, Au-MPA-DFO-Fe(III), are prepared via in-situ and ex-situ approaches for the first time and described by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS) and scanning tunneling microscopy (STM) techniques. The assemblies formed via the two approaches show different structures, topologies, and electrochemical kinetics. The STM images show that the Au-MPA-DFO layer is formed in rodlike arrays with 3À4 nm peak-to-peak distances, while the arrays of the Au-MPA-DFO-Fe(III) layers formed by the in-situ and ex-situ methods, respectively with sharp and round ridges, have similar peak-to-peak distances of 2À3 nm. The CVs reveal that the Fe(III) ion immobilized by the ex-situ method is more stable by 14.48 kJ/mol. The relative amounts of the adsorbed Fe(III) ions via the in-situ and ex-situ methods, Γ ex-situ /Γ in-situ , obtained by CV and EIS are 1.33 ( 0.13 and 1.37 ( 0.19, respectively. Faradaic and impedimetric surface titrations both predict a surface-pK a of ∼9.4 for the Au-MPA-DFO self-assembled monolayer (SAM).

Sulfur-doped graphene as a catalyst support: Influences of carbon black and ruthenium nanoparticles on the hydrogen evolution reaction performance

“…The EIS is a powerful, nondestructive and informative technique [43,44] which is usually used for characterization of the fuel cells and batteries [45,46], sensors and biosensors [47,48], and kinetics of the HER [49,50].…”

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

“…Electrochemical experimental setup, including instrumentation, measurements, acquisition and analysis of data, is described in our previous reports [30,34,35] This set-up results in ~10 6 number of radiation passages through the sample length of 2 nm, producing a spectrum intensity comparable to those collected for macroscopic samples with thickness of ~ 1.0 mm. Electrodes were kept in a vacuumed desiccator for 15 min prior to record the ATR-FTIR spectra.…”

“…The XPS results in conjunction with cathodic voltammetry desorption of MPA from Au-MPA, were used to assess the stoichiometry of the elements of the film components and their oxidation states. in the solution phase [30,36] or confined on the surface [34,35]. Background currents can also be used for this purpose [53].…”

“…Among several neutral redox probes, like FcMeOH [34,56], ascorbic acid, dopamine [52,57] and PBQ [58] used to trace modification of the electrode surface, the FcMeOH probe was found to be the most appropriate, because it neither modifies the background current Table 2.…”

“…The structure of SAMs can be controlled at molecular scale for engineering and designing the electronic devices [31,32], therefore, SAMs are themselves nanostructures [33]. These nanostructures have served as interesting platforms to address many physicochemical questions about electron transfer process at the electroactive [34,35] or electroinactive [36][37][38] moieties by confining the process at the electrode/solution interface. It is also well known that SAMs can increase or decrease electrode work function depending on the polarization of the dipole layer [39][40][41][42].…”