State of the Surface of Antibacterial Copper in Phosphate Buffered Saline. Issue 12 (9th August 2017)

• Record Type: Journal Article
• Authors: Toparli, Cigdem; Hieke, Stefan W.; Altin, Abdulrahman; Kasian, Olga; Scheu, Christina; Erbe, Andreas
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 12(2017)
• Page Start: H734
• Page End: H742
• Publication Date: 2017-08-09
• Subjects: antimicrobial surfaces -- chloride -- copper -- corrosion -- defects -- dissolution -- oxide formation -- passivity -- pitting; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0351712jes
• Languages: English
• ISSNs: 0013-4651

Abstract

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, Cu2 O and Cu4 O3 were observed when polarizing the system above ≈ −0.05 V vs. Ag|AgCl|3M KCl. The formation of Cu2 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 Cu2 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 Cu2 O-like surface, with Cu II complexes present in solution.