Odd鈥揈ven Effect in the Polymorphism of Self-Assembled Monolayers of Biphenyl-Substituted Alkaneselenolates on Au(111)
详细信息 查看全文
- 作者：Maciej Dendzik ; Andreas Terfort ; Piotr Cyganik
- 刊名：The Journal of Physical Chemistry C
- 出版年：2012
- 出版时间：September 13, 2012
- 年：2012
- 卷：116
- 期：36
- 页码：19535-19542
- 全文大小：585K
- 年卷期：v.116,no.36(September 13, 2012)
- ISSN：1932-7455
文摘
Self-assembled monolayers (SAMs) of 蠅-(4鈥?methylbiphenyl-4-yl) alkaneselenolates CH3(C6H4)2(CH2)nSe鈥?/sup> (BPnSe, n = 2鈥?) on Au(111) substrates, prepared in solution at elevated temperature (333 K), were studied using scanning tunneling microscopy (STM). Molecularly resolved images reveal that even-numbered BPnSe SAMs form two or three different coexisting phases, including the one observed at room temperature. In contrast, odd-numbered species exhibit only a single phase, which is the same as the one observed at room temperature, i.e. close to a commensurate oblique (2鈭?脳鈭?)R30掳 structure with two molecules per unit cell. Importantly, one of the phases observed for even-numbered BPnSe/Au(111) at room temperature (伪-phase) has a well-defined periodicity only in 1D, whereas the new additional phases observed at elevated temperature are fundamentally different and have 2D periodic character, exhibiting a commensurate rectangular 5脳2鈭? lattice with four molecules per unit cell (尾-phase) and an incommensurate oblique 2鈭?脳1.2鈭? lattice with two molecules per unit cell (纬-phase). For all systems, partial reorientation of the Au(111) step edges was observed upon SAM formation, indicating significant mobility of the topmost gold atoms induced by the adsorbates. To elucidate the effect of the S 鈫?Se substitution on the SAMs structure on Au(111), present results for BPnSe/Au(111) systems are discussed in view of the previously reported microscopic, spectroscopic, and desorption data obtained for these SAMs and for their thiol analogs, i.e. for BPnS/Au(111).