Effect of the pH in the growth of benzotriazole model layers at realistic environmental conditions

Highlights: • Upon benzotriazole adsorption, Cu is in the + 1 oxidation state essentially. • Layers prepared at different pH are chemically different. • BTAH and Cl adsorption are competitive: BTAH effectively replaces Cl. • Adsorbate growth limited to a single layer; no polymerisation is seen. • Adlayers exhibit very similar morphologies regardless of pH and immersion time. - Abstract: The growth of benzotriazole (BTAH) via solution deposition onto copper monolayers prepared via underpotential deposition (UPD) on Au(111)/mica substrates has been investigated using X-ray photoelectron spectroscopy (XPS) and ambient scanning tunnelling microscopy (STM) as a function of solution pH and immersion time. It is found that adsorbed species are sensitive to the solution pH, with a higher benzotriazole surface concentration following deposition from a more acidic environment. Although the layers prepared at different pH are chemically different, as highlighted by XPS, similar morphologies are recorded via STM. These results are critically discussed in the light of some of the adsorption models previously reported.