Self-Assembled Monolayer Formation from Decaneselenol on Polycrystalline Gold As Characterized by Electrochemical Measurements, Quartz-Crystal Microbalance, XPS, and IR Spectroscopy

Abstract

Self-assembled monolayer (SAM) formation from decaneselenol on gold substrate surfaces was studied using electrochemical measurements, reflection−absorption Fourier transform infrared spectroscopy (FT-IRRAS), X-ray photoelectron spectroscopy (XPS), and quartz-crystal microbalance (QCM). The Au substrate modified with the SAMs showed clear IR absorption bands corresponding to the CH stretches while distinct photoemission peaks were observed at C 1s, Se 3d, and Se 3p core levels in its XPS spectrum. Using a quartz-crystal microbalance, the surface coverage by the SAM-forming molecule was determined to be 0.88 nmol cm-2. Electrochemical impedance measurements revealed frequency-dependent capacitive behavior of the SAM, and the equivalent parameter was determined to be 6.1 × 10-6 sφ Ω-1 cm-1 (φ = 0.94). It also showed that the surface coverage of 99.8% can be attained, resulting in the suppression of a heterogeneous electron-transfer rate constant for a redox species dissolved in solution phase. The dielectri...