RESUMO
Displacement processes of pre-adsorbed 1-admanetanethiol (ADT) self-assembled monolayers (SAMs) on Au(111) by 1-hexanethiol (HT) at room temperature were investigated by scanning tunneling microscopy (STM) and cyclic voltammetry (CV). Molecular-scale STM imaging clearly revealed that phase transitions from the (7 × 7) phase for ADT SAMs to the c(4 × 2) phase for HT SAMs via intermediate phase including bright aggregated islands and disordered phase. Moreover, it was found that ADT SAMs were completely displaced by HT molecules with a short hexyl chain within an hour. The CV measurements showed that cathodic peaks for SAM-modified Au(111) electrodes as a function of displacement time were varied with the structural change of displaced SAMs. Our results provide new insight into understanding the displacement processes of ADT SAMs on Au(111) by HT.
RESUMO
Solvent effect on the formation and electrochemical behavior of octaneselenolate (C8Se) self-assembled monolayers (SAMs) on Au(111) derived from the adsorption of octaneselenocyanate (C8Se-CN) molecules in various solvents at 363 K for 1 h was examined by scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM imaging clearly revealed that the formation and structure of C8Se SAMs were markedly influenced by the polarity of solvent. C8Se SAMs formed in octane were composed of liquid-like disordered phase. In contrast, C8Se SAMs formed in DMF had ordered domains but not a uniform surface, whereas C8Se SAMs formed in ethanol had uniform surface and highly ordered domains with a (2 × 2 â13) structure. It was found that the structural quality of C8Se SAMs increased with increasing solvent polarity in the order of ethanol > DMF > octane. CV measurements also showed that blocking efficiency of C8Se SAMs for electrode reaction increased with increasing the structural quality of SAMs.
