Analytical and Bioanalytical Chemistry

, Volume 407, Issue 27, pp 8197–8204

Tip-enhanced Raman spectroscopic imaging shows segregation within binary self-assembled thiol monolayers at ambient conditions

  • Wan-Ing Lin
  • Feng Shao
  • Bruno Stephanidis
  • Renato Zenobi
Research Paper

DOI: 10.1007/s00216-015-8840-x

Cite this article as:
Lin, WI., Shao, F., Stephanidis, B. et al. Anal Bioanal Chem (2015) 407: 8197. doi:10.1007/s00216-015-8840-x
Part of the following topical collections:
  1. Nanospectroscopy

Abstract

Phase segregation of coadsorbed thiol molecules on a gold surface was investigated with nanoscale chemical imaging using tip-enhanced Raman spectroscopy (TERS). Samples were prepared using mixed solutions containing thiophenol (PhS) and an oligomeric phenylene-ethynylene (OPE) thiol, with 10:1, 2:1, and 1:1 molar ratios. Phase segregation into domains with sizes from ≈30 to 240 nm is observed with these molar ratios. A comparison of TERS images with different pixel sizes indicates that a pixel size bigger than 15 nm is not reliable in defining nanodomains, because of undersampling. In this study, the formation of nanodomains was clearly evident based on the molecular fingerprints provided by TERS, while ambient scanning tunneling microscopy (STM) was not capable of discerning individual domains via their apparent height difference. TERS therefore allows to image nanodomains in binary self-assembled monolayers, which are invisible to methods solely relying on topographic or electron density characteristics of self-assembled monolayers. Moreover, TERS mapping provides statistical data to describe the distribution of molecules on the sample surface in a well-defined manner. Peak ratio histograms of selected TERS signals from samples prepared with different mixing ratios give a better understanding of the adsorption preference of the thiols studied, and the relationship of their mixing ratio in solution and adsorbed on the surface.

Keywords

Thiols Raman spectroscopy Imaging Self-assembled monolayers TERS Segregation 

Supplementary material

216_2015_8840_MOESM1_ESM.pdf (976 kb)
ESM 1(PDF 976 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Wan-Ing Lin
    • 1
  • Feng Shao
    • 1
  • Bruno Stephanidis
    • 1
  • Renato Zenobi
    • 1
  1. 1.Department of Chemistry and Applied BiosciencesETH ZurichZurichSwitzerland

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