Relationship between packing structure and headgroups of self-assembled monolayers on Au(111): Bridging experimental observations through computer simulations

Journal of Physical Chemistry B

Volumn 102, Issue 16, 1998, Pages 2935-2946

  Li, Ta Wei ^a   Chao, Ito ^a   Tao, Yu Tai ^a  

^a INSTITUTE OF CHEMISTRY   (Taiwan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000842833     PISSN: 15206106     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp980049f     Document Type: Article

References (46)

1. Bain, C. D.; Whitesides, G. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 506.
2. Whitesides, G. M.; Laibinis, P. E. Langmuir 1990, 6, 87.
3. Laibinis, P. E.; Nuzzo, R. G.; Whitesides, G. M. J. Phys. Chem. 1992, 96, 5097.
4. Ulman, A. An Introduction to Thin Organic Films: From Langmuir - Blodgett to Self-Assembly; Academic Press: Boston, MA, 1991.
5. Prasad, P. N.; Williams, D. Introduction to Nonlinear Optical Effects in Molecules and Polymers; Wiley-Interscience: New York, 1991.
6. (a) Jackman, R. J.; Wilbur, J. L.; Whitesides, G. M. Science 1995, 269, 664.
7. (b) Wolf, M. O.; Fox, M. A. Langmuir 1996, 12, 955.
8. (a) Nuzzo, R. G.; Korenic, E. M.; Dubois, L. H. J. Chem. Phys. 1990, 93, 767.
9. (b) Nuzzo, R. G.; Dubois, L. H.; Allara, D. L. J. Am. Chem. Soc. 1990, 112, 558.
10. Bryant, M. A.; Pemberton, J. E. J. Am. Chem. Soc. 1991, 113, 8284.
11. (a) Rovida, G.; Pratesi, F. Surf. Sci. 1981, 104, 609.
12. (b) Strong, L.; Whitesides, G. M. Langmuir 1988, 4, 546.
13. (a) Fenter, P.; Eisenberger, P.; Liang, K. S. Phys. Rev. Lett. 1993, 70, 2447.
14. (b) Camillone, N., III; Chidsey, C. E. D.; Eisenberger, P.; Fenter, P.; Li, J.; Liang, K. S.; Liu, G.-Y.; Scoles, G. J. Chem. Phys. 1993, 99, 744.
15. Camillone, N., III; Chidsey, C. E. D.; Liu, G.-y.; Scoles, G. J. Chem. Phys. 1993, 98, 3503.
16. Alves, C. A.; Smith, E. L.; Porter, M. D. J. Am. Chem. Soc. 1992, 114, 1222.
17. Widrig, C. A.; Alves, C. A.; Porter, M. D. J. Am. Chem. Soc. 1991, 113, 2805.
18. Poirier, G. E.; Tarlov, M. J. Langmuir 1994, 10, 2853.
19. Poirier, G. E.; Tarlov, M. J.; Rushmeier, H. E. Langmuir 1994, 10, 3383.
20. Delamarche, E.; Michel, B.; Gerber, C.; Anselmetti, D.; Güntherodt, H.-J.; Wolf, H.; Ringsdorf, H. Langmuir 1994, 10, 2869.
21. Anselmetti, D.; Baratoff, A.; Güntherodt, H. J.; Delamarche, E.; Michel, B.; Gerber, C; Kang, H.; Wolf, H. Europhys. Lett. 1994, 27, 365.
22. Mar, W.; Klein, M. L. Langmuir 1994, 10, 188.
23. Sellers, H.; Ulman, A.; Shnidman, Y.; Eilers, J. E. J. Am. Chem. Soc. 1993, 115, 9389.
24. Pertsin, A. J.; Grunze, M. Langmuir 1994, 10, 3668.
25. Hautman, J.; Klein, M. L. J. Chem. Phys. 1990, 93, 7483.
26. Chang, S.-C.; Chao, L; Tao, Y.-T. J. Am. Chem. Soc. 1994, 116, 6792.
27. Dhirani, A.-A.; Zehner, R. W.; Hsung, R. P.; Guyot-Sionnest, P.; Sita, L. R. J. Am. Chem. Soc. 1996, 118, 3319.
28. Spellmeryer, D. C.; Grootenhuis, P. D. J.; Miller, M. D.; Kuyper, L. F.; Kollman, P. A. J. Phys. Chem. 1990, 94, 4483.
29. Lii, J.-H.; Allinger, N. L. J. Am. Chem. Soc. 1989, 111, 8576.
30. Walczak, M. M.; Chung, C.; Stole, S. M.; Widrig, C. A.; Porter, M. D. J. Am. Chem. Soc. 1991, 113, 2370.
31. We have studied short-chain n-alkanethiols and 4′-alkoxybiphenyl-4-thiols (C = 4, 5) with a (√3 × √3) lattice, which is the fundamental binding site of SAMs on Au(111), and did not find any conclusive results to explain the diminishing odd - even effect from the short-chain thiols to long-chain thiols. A recent STM observation showed that it took 50 h for butanethiols on Au(111) to grow into a saturated complex domain of packing patterns. And, the basic repeat unit of the saturated packing structure is the p × √3 superlattice, where 8≤ p ≤ 10 or p can be 7. Therefore, either before or after the saturated crystallization, the packing space of butanethiols on Au(111) is larger than the fundamental (√3 × √3) space of SAMs on Au(111). Owing to the uncertainty of the packing space, a precise energy function to describe the mobility of SAMs on Au(111) is important. However, up to now, there is still no good energy function to describe it. References for STM observation of liquidlike SAMs on Au(111) are the following: Poirier, G. E.; Tarlov, M. J. J. Phys. Chem. 1995, 99, 10966. Kang, J.; Rowntree, P. A. Langmuir 1996, 12, 2813.
32. We have studied short-chain n-alkanethiols and 4′-alkoxybiphenyl-4-thiols (C = 4, 5) with a (√3 × √3) lattice, which is the fundamental binding site of SAMs on Au(111), and did not find any conclusive results to explain the diminishing odd - even effect from the short-chain thiols to long-chain thiols. A recent STM observation showed that it took 50 h for butanethiols on Au(111) to grow into a saturated complex domain of packing patterns. And, the basic repeat unit of the saturated packing structure is the p × √3 superlattice, where 8≤ p ≤ 10 or p can be 7. Therefore, either before or after the saturated crystallization, the packing space of butanethiols on Au(111) is larger than the fundamental (√3 × √3) space of SAMs on Au(111). Owing to the uncertainty of the packing space, a precise energy function to describe the mobility of SAMs on Au(111) is important. However, up to now, there is still no good energy function to describe it. References for STM observation of liquidlike SAMs on Au(111) are the following: Poirier, G. E.; Tarlov, M. J. J. Phys. Chem. 1995, 99, 10966. Kang, J.; Rowntree, P. A. Langmuir 1996, 12, 2813.
33. Mayo, A. L.; Olafson, B. D.; Goddard, W. A., III. J. Phys. Chem. 1990, 94, 8897.
34. Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F. J. Am. Chem. Soc. 1985, 107, 3902.
35. 2, version 2.0, BIOSYM/Molecular Simulations Inc., 1995.
36. Sabatani, E.; Cohen-Boulakia, J.; Bruening, M.; Rubinstein, I. Langmuir 1993, 9, 2974.
37. Nosé, S. J. J. Chem. Phys. 1984, 91, 511.
38. Siepmann, J. I.; McDonald, I. R. Langmuir 1993, 9, 2351.
39. Our calculations showed that the most favored packing domain for both types of thiols is one chain per unit cell. This is different from the results obtained by Mar and Klein for n-alkanethiol (C = 15), in which two chains per unit cell was shown as the lowest-energy packing structure. It is possibly because our model includes electrostatic interaction for the alkyl part; when electrostatic interaction was turned off, we also found two chains per unit cell as the lowest-energy packing structure.
40. 3 chemisorption and for 4′-alkoxy-biphenyl-4-thiols. Their minimized ΔE values are two (to three) times higher than that for other packing structures. Furthermore, these packing structures are all unstable at 298 K and changed into either one chain per unit cell or two chains per unit cell during MD simulations.
41. Since the packing parameters (θ, φ) of the alkyl part of the aromatic-derivatized thiols are similar to that of n-alkanethiols, the energy difference estimation was based on the potential energy difference of structures A and B of n-alkanethiols (Table 2).
42. Typical profiles of MD results with respect to time can be found in the Supporting Information section.
43. CH3〉.
44. For example, the model used in the ab initio study involves a cluster in which the Au atoms are not allowed to relax upon sulfur binding.
45. We are convinced that the bending flexibility of sulfur on gold is larger than that of oxygen in an organic moiety in view of the participation of multiple gold atoms in a Au(surface)-S bond (see ref 19). The gold atoms can fulfill different bonding demands of sulfur in different Au-S-C bending angles more easily than the neighboring groups of oxygen in alkoxybiphenylthiols can. Therefore, the low energy difference and barrier calculated by Sellers (ref 19) for sulfur angle variation is reasonable.
46. Tao, Y.-T.; Pandiaraju, S.; Lin, W. L. Paper in preparation.