Electro-assisted assembly of aliphatic thiol, dithiol and dithiocarboxylic acid monolayers on copper

Inhibition Effect of Three-Dimensional (3D) Nanostructures on the Corrosion Resistance of 1-Dodecanethiol Self-Assembled Monolayer on Copper in NaCl Solution

A novel and simple method to improve the corrosion resistance of copper by constructing a three-dimensional (3D) 1-dodecanethiol self-assembled monolayer (SAM) in 3.5% NaCl solution is reported in this study. Several drops of 1% H₃PO₄ solution are thinly and uniformly distributed on copper surface to form a 3D nanostructure constituted by Cu₃(PO₄)₂ nanoflowers. The anticorrosion properties of 1-dodecanethiol SAM on copper surface and on copper surface that is treated with H₃PO₄ solution were evaluated. Results demonstrated that 1-dodecanethiol SAM on bare copper surface exhibits good protection capacity, whereas a copper surface that is pretreated with H₃PO₄ solution can substantially enhance the corrosion resistance of 1-dodecanethiol SAM.

Preparation and characterization of alkylphosphonic acid self-assembled monolayers on titanium alloy by chemisorption and electrochemical deposition

Ti-6Al-4V alloy is the most commonly used alloy for dental and orthopedic implants. In order to improve osseointegration, different surface modification methods are usually employed, including self-assembled monolayers (SAMs). This study presents an investigation of both active (electroassisted) and passive (adsorption) approaches for the modification of Ti-6Al-4V using alkylphosphonic acid. The monolayers were characterized by cyclic voltammetry, double-layer capacitance, contact angle measurements, X-ray photoelectron spectroscopy, polarization modulation infrared reflection adsorption spectroscopy, electrochemical impedance spectroscopy, and corrosion potentiodynamic polarization measurements. It is shown that the electrochemically assisted monolayers, which are assembled faster, exhibit better control over surface properties, a superior degree of order, and a somewhat higher packing density. The electrosorbed SAMs also exhibit better blockage of electron transfer across the interface and thus have better corrosion resistance.

Electrochemical and spectroscopic study of the self-assembling mechanism of normal and chelating alkanethiols on copper

The self-assembly of aliphatic thiol (RSH), dithiol (R(SH)(2)), and dithiocarboxylic acid (RS(2)H) onto mildly oxidized and highly oxidized copper was studied in real time by in situ electrochemical impedance spectroscopy (EIS). Ex situ characterization of the films was carried out using linear sweep voltammetry (LSV), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). In situ EIS studies found a very fast adsorption of RSH, R(SH)(2), and RS(2)H (within 10-15 s). This fast adsorption step is followed by the long-term additional adsorption and consolidation of SAM. However, the self-assembly of RS(2)H passes through an intermediate step of molecule rearrangement for around 10 to 30 min after around 2 to 7 min of self-assembly. The binding of both sulfur moieties of R(SH)(2) with Cu happens simultaneous. The oxide reduction capacity of RSH, R(SH)(2), and RS(2)H was good. However, the XPS studies showed the decomposition of RS(2)H-based SAMs to Cu(2)S. Monolayers prepared on both mildly oxidized and heavily oxidized Cu with R(SH)(2) had the highest stability. Monolayers of RS(2)H showed the least stability on both mildly oxidized and heavily oxidized Cu. Although RSH-based SAMs had good organization on both mildly oxidized and highly oxidized Cu, R(SH)(2)-based SAMs did not show good organization in either case. The RS(2)H monolayer had good organization only on mildly oxidized Cu.