State of the Surface of Antibacterial Copper in Phosphate Buffered Saline

Abstract

The state was investigated of the copper surface in phosphate buffered saline (PBS; 140 mM Cl − , 10 mM phosphate; pH 7) by a combination of cyclic voltammetry (CV) and chronoamperometry (CA) with in situ spectroscopic ellipsometry and Raman spectroscopy. After polarization, samples were analyzed ex situ. In agreement with expectations on the basis of the Pourbaix diagram, Cu 2 O and Cu 4 O 3 were observed when polarizing the system above ≈−0.05 V vs. Ag|AgCl|3M KCl. The formation of Cu 2 O did not lead to a passivation of the system. Rather, the system dissolved under formation of soluble square planar CuCl 2− 4 , identified by its strong Raman peak ≈300 cm −1 . During dissolution, spectroscopic ellipsometry showed a film with a stable steady state thickness. Energy electron loss spectroscopy (EELS) analysis of a cross section of the oxide after removal from the electrolyte showed that the oxide was Cu 2 O. It is suggested that Cl − replaces oxygen vacancies in the oxide layer. As soon as oxidation to Cu II becomes dominant, the dissolution proceeds to soluble Cu II species. The outer surface of copper under these conditions is hence a Cu 2 O-like surface, with Cu II complexes present in solution.

Alkaline manganese electrochemistry studied byin situandoperandospectroscopic methods – metal dissolution, oxide formation and oxygen evolution

“…In former studies our group successfully employed in situ spectroscopic ellipsometry (SE) to probe metal supported oxide layer thicknesses simultaneously with spectral changes that can be attributed to composition changes in electrochemical setups. [24][25][26] It was shown that passive oxide films forming on Cu dissolve because of single charge oxygen vacancy formation during the OER. 25 In situ and operando measurements on metallic Cu showed that metastable Cu 4 O 3 forms before the oxide dissolution.…”

“…27 Most importantly, the structure and properties of thin oxide films formed in electrochemical processes can significantly deviate from those found in the respective bulk system. [24][25][26][28][29][30] Different compositions and stability of different manganese oxides with respect to pH and electrode potential can be accessed through the Pourbaix diagram (cf. Fig.…”

Photocorrosion of n‐ and p‐Type Semiconducting Oxide‐Covered Metals: Case Studies of Anodized Titanium and Copper

“…At the metal–electrolyte interface, the dissolution reaction must involve an oxidation, which could, for example, proceed via a localized reaction with oxygen to a soluble Cu 2+ species. [ 54,55 ]…”

“…At the metal-electrolyte interface, the dissolution reaction must involve an oxidation, which could, for example, proceed via a localized reaction with oxygen to a soluble Cu 2þ species. [54,55] Mott-Schottky analysis for copper indicates p-type behavior, and the positive photovoltage and cathodic photocurrent measurements indicate that electrons migrated toward the oxide-electrolyte interface. Therefore, a process where electrons contribute to accelerated cathodic reaction and thereby accelerate the corrosion rate is proposed.…”

The multiple roles of an organic corrosion inhibitor on copper investigated by a combination of electrochemistry-coupled optical in situ spectroscopies

“…The decrease of Cu 4 O 3 peak is interpreted as transformation of Cu 4 O 3 to other copper oxides, presumably CuO, at higher electrode potential. (Alternatively, soluble Cu 2+ species may also form [47].) During the negative scan, the peak at 523 cm −1 increased, implying the reformation of Cu 4 O 3 .…”