Structure and identity of 4,4′-thiobisbenzenethiol self-assembled monolayers

Yuling Wang, Linfeng Gan, Hongjun Chen, Shaojun Dong*, Jin Wang

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Self-assembled monolayers (SAMs) of 4,4′-thiobisbenzenethiol (TBBT) can be formed on Au surface spontaneously. The structural characteristics and adsorption behavior of TBBT SAMs on Au have been investigated by surface enhanced Raman scattering (SERS), electrochemical cyclic voltammetry (CV), ac impedance spectroscopy (EIS), and atomic force microscopy (AFM). It is demonstrated that TBBT adsorbed on Au by losing a H atom, forming one Au-S bond, and the other mercapto group is free at the surface of the monolayer owing to the presence of the vS-H at 2513 cn-1 and the δC-S-H at 910 cm-1 in SERS. The enhancement of the vibration of C-S (1064 cm-1), the aromatic C-H vibration (3044 cm-1), and the absence of the vibration of S-S illustrate TBBT adsorbed on Au forming a monolayer with one benzene ring tilted with respect to the Au surface. The interpretation of the observed frequencies is aided by ab initio molecular' orbital (MO) calculations at the HF/6-31G* level of theory. Electrochemical CV and EIS indicate TBBT monolayers can passivate the Au effectively for its low ratio of pinhole defects (θ = 99.6%). AFM studies give details about the surface morphology. The applications of TBBT SAMs have been extensively investigated by exposure of Cu2+ ion to TBBT SAMs on Au and covalent adsorption of metal nanoparticles. Electrochemical, X-ray photoelectron spectroscopic, and SERS results indicate that Cu2+ can react with TBBT SAMs and present on TBBT SAMs as Cu(I). A scanning electron microscopic image of Ag nanoparticles on TBBT/Au and the Raman spectrum of TBBT in smooth macroscopic Au/TBBT SAMs/Ag nanoparticle sandwich structure indicate that metal nanoparticles can be adsorbed on TBBT SAMs effectively through covalent linkage.

Original languageEnglish
Pages (from-to)20418-20425
Number of pages8
JournalJournal of Physical Chemistry B
Volume110
Issue number41
DOIs
Publication statusPublished - 19 Oct 2006
Externally publishedYes

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