In Situ STM Imaging of Fused Thienothiophene Molecules Adsorbed on Au(111) Electrode

• Main Authors: Ya-hua Hsu, 許雅華
• Other Authors: Shueh-Lin Yau
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/10099776152526924171

碩士 === 國立中央大學 === 化學研究所 === 99 === In situ scanning tunneling microscopy (STM) was used to reveal the spatial structures of thienothiophene derivatives deposited onto Au(111) electrode from 50 to 100 μM solutions indichlorobenzene. First, the structures of DP-DTT (C6H5-DTT-C6H5), FPP-DTT(C6F5-DTT-C6H5) and DFP-DTT (C6F5-DTT-C6F5) deposited onto Au(111) electrode were examined. For DP-DTT, a disordered adlayer was seen at E > 0.3 V (vs. reversible hydrogen electrode) and was converted into a highly ordered (2 × 7√3)rect - 2 DP-DTT structure when the potential was shifted to 0.2 V. This ordered structure was stable for hours within this potential range. However, switching the potential further more negative to 0 V resulted in the slow desorption of the molecules. The (2 × 7√3)rect - 2DP-DTT ordered adlattices were restored when the potential was made positive to 0.2 V. On the other hand, FPP-DTT was found to arrange in (√21 × 3√19) and (12 × √21) ordered adlattices. Admolecules in both structures were arranged in pairs resulting from dipole – dipole interactions between the phenyl and pentafluorophenyl substituents at room temperature (25。C). In strong contrast to the first two molecules, no ordered structures were observed for DFP-DTT under all experimental conditions employed in this study. Second, the structures of diphenyl (DP- ) – substituted thieno[3,2-b]thieno[2'',3'':4,5]thieno[2,3-d]thiophene (TTA) deposited on Au(111) electrode were examined。While DP-TTA arranges in well-ordered (2 × √39) and (?21 × √39) structures. The adsorption of DP-TTA varied with experimental conditions, including sample concentration, dosing time and dosing temperature. Lastly, the structures of dibenzoyl (DB- ) - substituted and pentafluorobenzoyl (FBB- )- substituted dithieno[2,3-b:3,2-d]thiophene (DTT) molecules deposited onto Au(111) electrode were studied. DB-DTT formed protracted molecular rows separated by 19 ~ 27 Å. Such a unique arrangement could be ascribed to unlike intermolecular interactions associated with individual molecules with drastically different molecular symmetry. FBB-DTT formed a (4 × 4√3) structure, whose internal molecules structures were discerned by high-resolution STM.Phenyl groups without fluoro-substitutents are considered more electron-rich than those with fluoro-substituent. This disparity in charge distribution is thought to be responsible for their corrugated STM appearances. The former appeared to be 0.04 nm higher than the latter.