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Molecular-scale investigation of structural changes in cyclohexanethiol self-assembled monolayers on Au(111)
Hungu Kang1, Chang-Hyun Jang, Masahiko Hara
1Department of Chemistry, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
Journal of Nanoscience and Nanotechnology
|November 14, 2009
Summary
Cyclohexanethiol (CHT) self-assembled monolayers (SAMs) on gold surfaces exhibit distinct 2D phase transitions influenced by solution concentration. These structural dynamics differ from alkanethiols, offering insights into cyclic thiol SAMs.
Area of Science:
- Surface Science
- Materials Chemistry
- Nanotechnology
Background:
- Self-assembled monolayers (SAMs) are crucial for modifying surface properties.
- Cyclic thiols like cyclohexanethiol (CHT) present unique self-assembly behaviors compared to linear alkanethiols.
- Understanding SAM structure is key to controlling interfacial phenomena.
Purpose of the Study:
- To investigate the two-dimensional (2D) ordered structures of cyclohexanethiol (CHT) SAMs on Au(111).
- To explore the influence of solution concentration on CHT SAM phase transitions.
- To compare the self-assembly behavior of CHT SAMs with alkanethiol SAMs.
Main Methods:
- Fabrication of CHT SAMs on Au(111) using varying solution concentrations.
- High-resolution molecular-scale imaging using Scanning Tunneling Microscopy (STM).
Main Results:
- Observed 2D phase transitions of CHT SAMs: (2 x 4√2)R20° to (5√15)R25° (intermediate) to (5 x 2√3)R35°.
- The (5 x 2√3)R35° phase formed at high concentrations, low temperatures, or long immersion times.
- Confirmed fully covered SAM structures with molecular packing arrangements.
- Highlighted distinct 2D SAM formation dynamics for CHT compared to alkanethiols due to CHT ring structural dynamics.
Conclusions:
- Solution concentration, temperature, and immersion time significantly control CHT SAM phase and structure.
- The structural dynamics of the cyclohexanethiol ring are critical to its self-assembly behavior.
- These findings provide valuable insights into the structural behavior of cyclic thiol SAMs on surfaces.
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