Nitroxyl radical self assembled monolayers: Ion pairing investigation in organic and aqueous media

Self assembled monolayers (SAMs) formed from TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative thiols have been studied by electrochemical quartz crystal microbalance (EQCM) in both aqueous and non-aqueous solvents. The in situ study of the mass transport occurring during the oxidation of TEMPO provides evidence of a ion pair formation without incorporation of solvent in densely packed nitroxyl radical SAMs. For SAMs having a low nitroxyl radical surface coverage, the effect of mixed SAMs is evidenced and seems to avoid the solvent incorporation.