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|標題:||Scanning Tunneling Microscopy and Cyclic Voltammetry Study of Self-Assembled 3,3 '-Thiobis(1-propanesulfonic acid, sodium salt) Monolayers on Au(111) Electrodes||作者:||Liu, Y.F.
|Project:||Journal of Physical Chemistry C||期刊/報告no：:||Journal of Physical Chemistry C, Volume 115, Issue 15, Page(s) 7638-7647.||摘要:||
Self-assembled monolayers (SAMs) of 3,3'-thiobis(1-propane-sulfonic acid, sodium salt) (TBPS) on Au(111) electrodes have been characterized by scanning tunneling microscopy and cyclic voltammetry in aqueous perchloric acid solutions. TBPS exhibits an adsorption behavior typically observed for dialkyl sulfides including intact adsorption and low coverage phases with molecules predominantly lying flat on the surface. On the other hand, an untypical chemical bond and well domains were determined which resemble the characteristics of alkenethiol SAMs. When the adlayer was prepared at its open circuit potential (OCP), a (6 x 3 root 3) TBPS adlayer phase was observed at potentials E > 0.7 V(RHE) in TBPS-free electrolyte. At more cathodic potentials, the adlayer transforms irreversible to a disordered phase. In contrast, in situ STM studies in TBPS-containing electrolyte reveal a very complex, potential-dependent adsorption behavior. With increasing electrode potential, the structure of the adlayer transforms in sequence from a disordered phase sigma, to a low coverage stripe phase alpha, to a high coverage stripe phase beta, and finally to a disordered aggregate phase sigma(a). The re verse cathodic sweep shows transitions from sigma(a) to beta, back to sigma(a), and to an ordered adlayer phase gamma. All of these phases significantly differ from the (6 x 3 root 3) phase oil are not transient phases at OCP. This behavior is attributed to the influence of the electrode potential on intermolecular and molecule - substrate interaction, as well is on the TBPS coverage Furthermore, the cathodic deposition of Au-TBPS complexes results in the formation of Au islands with fractal morphology.
|Appears in Collections:||化學工程學系所|
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