Authors: WanIng Lin Feng Shao Bruno Stephanidis Renato Zenobi
Publish Date: 2015/06/28
Volume: 407, Issue: 27, Pages: 8197-8204
Abstract
Phase segregation of coadsorbed thiol molecules on a gold surface was investigated with nanoscale chemical imaging using tipenhanced Raman spectroscopy TERS Samples were prepared using mixed solutions containing thiophenol PhS and an oligomeric phenyleneethynylene OPE thiol with 101 21 and 11 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 selfassembled monolayers which are invisible to methods solely relying on topographic or electron density characteristics of selfassembled monolayers Moreover TERS mapping provides statistical data to describe the distribution of molecules on the sample surface in a welldefined 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 surfaceThis work was financially supported by the SALSA program at Humboldt University Berlin and by the EMRP NEW02 project “Metrology for Raman spectroscopy” The EMRP is jointly funded by the participating countries within EURAMET and the European Union We would like to thank Lothar Opilik and Jacek Szczerbiński for helpful discussions
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