Langmuir, Vol.27, No.21, 13383-13389, 2011
Electrochemical and STM Studies of 1-Thio-beta-D-glucose Self-Assembled on a Au(111) Electrode Surface
In this study, a Au(111) electrode is functionalized with a monolayer of 1-thio-beta-D-glucose (beta-Tg), producing a hydrophilic surface. A monolayer of beta-Tg was formed on a Au(111) surface by either (1) potential-assisted deposition with the thiol in a supporting electrolyte or (2) passive incubation of a gold substrate in a thiol-containing solution. For each method, the properties of the beta-Tg monolayer were investigated using cyclic voltammetry (CV), differential capacitance (DC), and chronocoulometry. In addition, electrochemical scanning tunneling microscopy (EC-STM) was used to obtain images of the self-assembled monolayer with molecular resolution. Potential-assisted assembly of beta-Tg onto a Au(111) electrode surface was found to be complicated by oxidation of beta-Tg molecules. The EC-STM images revealed formation of a passive layer containing honeycomb-like domains characteristic of a formation of S-8 rings, indicating the S-C bond may have been cleaved. In contrast, passive self-assembly of thioglucose from a methanol solution was found to produce a stable, disordered monolayer of beta-Tg. Since the passive assembly method was not complicated by the presence of a faradaic process, it is the method of choice for modifying the gold surface with a hydrophilic monolayer.