Formation of Chiral Self-Assembled Structures of Amino Acids on Transition-Metal Surfaces: Alanine on Pd(111)
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- 作者：Mausumi Mahapatra ; Luke Burkholder ; Yun Bai ; Michael Garvey ; J. Anibal Boscoboinik ; Carol Hirschmugl ; Wilfred T. Tysoe
- 刊名：Journal of Physical Chemistry C
- 出版年：2014
- 出版时间：April 3, 2014
- 年：2014
- 卷：118
- 期：13
- 页码：6856-6865
- 全文大小：618K
- 年卷期：v.118,no.13(April 3, 2014)
- ISSN：1932-7455
文摘
The structure and self-assembly of alanine on Pd(111) is explored using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), reflection鈥揳bsorption infrared spectroscopy (RAIRS), and scanning tunneling microscopy (STM), and supplemented by density functional theory (DFT) calculations to explore the stability of the proposed surface structures formed by adsorbing alanine on Pd(111) and to simulate the STM images. Both zwitterionic and anionic species are detected using RAIRS and XPS, while DFT calculations indicate that isolated anionic alanine is significantly more stable than the zwitterion. This observation is rationalized by observing dimeric species when alanine is dosed at 270 K and then cooled to trap metastable surface structures. The dimers form due to an interaction between the carboxylate group of anionic alanine with the NH3+ group of the zwitterion. Adsorbing alanine at 290 K results in the formation of dimer rows and tetramers resulting in only short-range order, consistent with the lack of additional diffraction spots in LEED. The stability of various structures is explored using DFT, and the simulated STM images are compared with experiment. This enables the dimer rows to be assigned to the assembly of anionic-zwitterionic dimers and the tetramer to the assembly of two dimers in which three of the alanine molecules undergo a concerted rotation by 30掳.