Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

Published

March 14, 2006

Author(s)

D Y. Petrovykh, H Y. Kimura-Suda, A Opdahl, Lee J. Richter, Michael J. Tarlov, L J. Whitman

Abstract

We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that in all cases alkanethiols deposited from 1 mM ethanolic solutions formed densely packed monolayers (>5 1014 molecules/cm2) in which alkyl chains were oriented close to surface normal. Stored in the laboratory ambient, the monolayers were unchanged over about one week, but were largely oxidized in about one month. No evidence was found of molecules weakly bound within the monolayer or having undergone C-S bond scission, however, three distinct sulfur states were observed for all samples in the XPS of the S 2p region. The lowest and highest binding energy components are assigned to alkylthiolate and partially oxidized alkylthiolates species, respectively. The remaining S 2p component (1/3 of the sulfur layer), intermediate in binding energy between the other two components, is attributed to sulfur headgroups present as disulfide functionalities or bound to surface Pt oxides.

Citation

Langmuir

Volume

22

Issue

No. 6

Pub Type

Journals

Keywords

alkanethiol, molecular electronics, plantinum, self-assembled monolayers, XPS

Citation

Petrovykh, D. , Kimura-Suda, H. , Opdahl, A. , Richter, L. , Tarlov, M. and Whitman, L. (2006), Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers, Langmuir (Accessed April 26, 2024)