In Situ STM Revelation of the Adsorption and Polymerization of Aniline on Au(111) Electrode in Perchloric Acid and Benzenesulfonic Acid

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• 作者：Yihui Lee ; Sihzih Chen ; Hsinling Tu ; Shuehlin Yau ; Liangjen Fan ; Yawwen Yang ; Wei-Ping Dow
• 刊名：Langmuir
• 出版年：2010
• 出版时间：April 20, 2010
• 年：2010
• 卷：26
• 期：8
• 页码：5576-5582
• 全文大小：905K
• 年卷期：v.26,no.8(April 20, 2010)
• ISSN：1520-5827

文摘

In situ scanning tunneling microscopy (STM) was used to study the adsorption and polymerization of aniline on Au(111) single-crystal electrode in 0.1 M perchloric acid and 0.1 M benzenesulfonic acids (BSA) containing 30 mM aniline, respectively. At the onset potential of aniline’s oxidation, 0.8 V [vs reversible hydrogen electrode], aniline molecules were adsorbed in highly ordered arrays, designated as (3 × 2√3) and (4 × 2√3) in perchloric acid and BSA, respectively. These structures consisted of intermingled aniline molecules and perchlorate or BSA⁻ anions zigzagging in the 110 directions in HClO₄ and in the 121 directions in BSA. The coverage of aniline admolecule on Au(111) was lower in BSA than in HClO₄. Raising the potential to 0.9 V or more positive values triggered the oxidation and polymerization of aniline. With aniline molecules arranging in a way similar to the backbone of PAN in HClO₄, they readily coupled with each other to produce linear polymeric chains aligned predominantly in the 110 directions of the Au(111). Compared with the results observed in H₂SO₄ (Leeet al. J. Am. Chem. Soc. 2009, 131, 6468), the rate of polymerization was slower in HClO₄ and the produced PAN molecules tended to aggregate on the Au(111) electrode. PAN molecules generated in HClO₄ were anomalously shorter than those formed in H₂SO₄. In 0.1 M BSA, PAN molecules produced by small overpotential (η < 100 mV) could assume linear chains or 3D aggregates, depending on [aniline]. These results revealed molecular level details in electropolymerization of aniline, highlighting the important role of anion in controlling the conformation of PAN molecules and the texture of PAN film.