Achieving both nanopatterning and desired upright orientation with alkanedithiol self-assembled monolayers on gold

Keywords:
nanopatterning, thiol-terminated, self-assembled monolayers, AFM, nanografting

Abstract:
Organodithiols on noble metals such as gold are good candidates to generate thiol-terminated self-assembled monolayers (SAMs) if molecules can form a close-packed and standing-up layer on the substrate as the case of alkanethiols. However, dithiols usually yield lying-down or looped alkanedithiolates on gold via the binding of both SH groups when adsorbed layers are prepared from widely used natural growth approaches. Here, a new approach to circumvent that obstacle and achieve high-quality thiol-terminated assemblies is developed. It involves an atomic force microscopy (AFM)-based lithography method known as nanografting performed in a dithiol solution. Using aliphatic dithiols as an example, dithiol SAMs prepared by both natural growth and nanografting are well characterized by AFM. High-resolution imaging and height measurements clearly demonstrate that dithiol molecules are densely packed and adopt a standing-up conformation in the fabricated patterns of dithiol SAMs to present free SH groups on the surface. In addition, nanografting enables the fabrication of thiol-terminated layers on gold with nanometer-scale precision in geometry, size and location. Designed thiol-terminated nanostructures as surface temples to direct the metal deposition is also studied.

Nanotech 2008 Conference Program Abstract