Regeneration of Gold Surfaces Covered by Adsorbed Thiols and Proteins Using Liquid-Phase Hydrogen Peroxide-Mediated UV-Photooxidation

Quartz crystal microbalance (QCM) response of 6-mercapto-1-hexanol chemisorption was used as a model system for examining regeneration of gold (Au) surfaces covered by sulfur-based self-assembled monolayers (SAMs) using a liquid-phase UV-photooxidation (liquid-UVPO) technique. The treatment facilitated oxidation of the Au–thiolate bond in liquid as supported by time-of-flight matrix-free laser desorption/ionization mass spectrometry (LDI-TOF-MS) and post-treatment SAM reformation. The liquid-UVPO technique also showed the ability to regenerate Au surfaces covered by adsorbed proteins, demonstrated using bovine serum albumin (BSA). Comparison with Au regeneration achieved using standard piranha treatment showed the liquid-UVPO technique better preserved the original Au film properties than did piranha treatment. Piranha treatment was found to affect both surface morphology, in terms of surface roughness increase, and film crystal structure, in terms of Au ⟨111⟩ phase fractional decrease, that were relatively absent in the liquid-UVPO treatment based on atomic force microscopy (AFM) and X-ray diffraction (XRD) studies, respectively. This work gives a new liquid-phase technique for regenerating SAM- and protein-covered Au surfaces in liquid that better preserves the original properties of the Au film than standard piranha treatment. Thus, it has potential to improve measurement repeatability in sensing applications, which require Au surface regeneration.