Surface assembly and nanofabrication of 1,1,1-tris(mercaptomethyl)heptadecane on Au(111) studied with time-lapse atomic force microscopy

Tian Tian,Burapol Singhana,Jayne C Garno,T Randall Lee,Xianglin Zhai,Lauren E Englade-Franklin

doi:10.3762/bjnano.5.3

Abstract

The solution self-assembly of multidentate organothiols onto Au(111) was studied in situ using scanning probe nanolithography and time-lapse atomic force microscopy (AFM). Self-assembled monolayers (SAMs) prepared from dilute solutions of multidentate thiols were found to assemble slowly, requiring more than six hours to generate films. A clean gold substrate was first imaged in ethanolic media using liquid AFM. Next, a 0.01 mM solution of multidentate thiol was injected into the liquid cell. As time progressed, molecular-level details of the surface changes at different time intervals were captured by successive AFM images. Scanning probe based nanofabrication was accomplished using protocols of nanografting and nanoshaving with n-alkanethiols and a tridentate molecule, 1,1,1-tris(mercaptomethyl)heptadecane (TMMH). Nanografted patterns of TMMH could be inscribed within n-alkanethiol SAMs; however, the molecular packing of the nanopatterns was less homogeneous compared to nanopatterns produced with monothiolates. The multidentate molecules have a more complex assembly pathway than monothiol counterparts, mediated by sequential steps of forming S–Au bonds to the substrate.

Highlights

Multidentate thiol-based adsorbates attach to gold surfaces through multiple bonds that provide enhanced stability to selfassembled monolayers (SAMs) [1,2]
Studies of the elastic modulus of SAMS and protein films was accomplished in liquid media using force modulation atomic force microscopy (AFM) [30]
Investigations of surfaces throughout the course of chemical self-assembly reactions have been monitored with AFM in liquid media [27]

Summary

Introduction

Multidentate thiol-based adsorbates attach to gold surfaces through multiple bonds that provide enhanced stability to selfassembled monolayers (SAMs) [1,2]. To understand more completely the surface structure and self-assembly process for multidentate thiols, we chose a tridentate molecule, 1,1,1-tris(mercaptomethyl)heptadecane (TMMH) for in situ AFM studies. Side-by-side comparisons of the surface structures of multidentate adsorbates versus n-alkanethiol SAMs were accomplished using nanografting to give a local measurement of film thickness, referencing the well-known dimensions of n-alkanethiols as a baseline.

Results

Conclusion