| dc.description.abstract | Abstract
Ⅰ.Alkanethiol and Arythiol Molecules on Pt(111) and Au(111)
Pt(111)－This thesis is divided into three parts. First high-resolution scanning tunneling microscopy (STM) has been used to examine the real-space structures of alkanethiol (1-hexanethiol, 1-nonanethiol, 1-dodecanethiol, and 1-octadecanethiol) and arylthiol (benzenethiol and 4-hydroxybenzenethiol) on well-ordered Pt(111) electrodes in 0.1 M HClO4. The concentrations of organosulfur compounds in the aqueous dosing solutions, together with electrochemical potential, determine the coverage and spatial arrangements of these ad-molecules. For arylthiol, low and high dosages respectively result in (2 × 2), θ = 0.25 and (?3 × ?3)R30°, θ = 0.33 between 0.1 and 0.3 V. In contrast, all alkanethiol molecules examined in this study are adsorbed in (2 × 2) at a coverage of 0.25. The degree of ordering deteriorates substantially for all molecular adlayers at more positive potentials. The real-space structures of sulfur adatoms and organosulfur molecules are identical, suggesting the preponderance of surface bonding via the sulfur-ends of the ad-molecules. These organosulfur ad-molecules Pt(111) dramatically impede electron transfer of the 2e-/2H+ hydroquinone/benzo- quinone redox couple, whereas a monolayer of sulfur adatoms has little effect on the kinetics of this reaction.
Au(111)－Hexanethiol molecules are adsorbed in six order structures respectively (2?7 × ?57)、(7 × ?31)、(4 × 2?3)、(5 × ?19)、(?19 × ?31) 及(?13 × ?31)R85°, θ = 0.18 ~ 0.2. Furthermore, benzenethiol molecules result in (2?7 × ?31)、(?3 × ?21) and (2 × ?31), θ = 0.18 ~ 0.33.
Ⅱ. Cu electrodeposition on arylthiol-Pt(111)
Underpotential deposition of Cu atom results in islands randomly nucleated at thiol modified Pt(111) electrode. Nucleation of Cu adatoms preferential occurs at defects within the arylthiol monolayer, followed by lateral expansion of the nucleation seeds upon addition of more Cu adatoms. A full Cu adlayer covered the whole surface at the end of deposition according to the electrochemical results, the SAM monolayer exerts little effect on Cu deposition , as the charges contained in the stripping peak are insensitive to the prescence of SAM. Copper adatoms are likely to displace hexanethiol molecules and bond to the Pt substrate directly.
Ⅲ.Stilbene derivatives SAMs on transition metal
We employed in situ STM to study the adsorption of stilbene derivatives onto Au(111), Pt(111), and Rh(111) in 0.1 M HClO4. Expectedly, these organic molecules are adsorbed with their molecular paralled to planes the surface of Pt and Rh, but at Au(111) surface bonding is formed through the N-ends of there molecules and they are mostly vertically oriented. | en_US |