Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

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. Specifically, 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 on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that alkanethiols deposited from 1 mM ethanolic solutions on piranha-cleaned Pt formed densely packed monolayers in which alkyl chains were oriented close to the surface normal. Stored in the laboratory ambient, these monolayers were unchanged over about 1 week but were largely oxidized in about 1 month. No evidence was found of molecules being 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 alkylthiolate species, respectively. The remaining S 2p component (approximately one-third of the sulfur layer), intermediate in binding energy between the other two components, is attributed to a chemisorbed species with a S binding configuration distinct from the majority alkylthiolate: for example, S bound to Pt bound to O, S with a different Pt coordination number, or S in an adsorbed disulfide.

Membrane protein resistance of oligo(ethylene oxide) self-assembled monolayers

“…3A shows that the SAMs of all four compounds are similar on Au and Pt with the SAMs of 1 thicker than those of 2-4. SAM thickness differences on Au and Pt for 1-4 are small, similar to that observed for n-alkanethiol SAMs [34], and support the use of Pt for further studies involving IMPs (Fig. 1).…”

“…4 A, significantly more Rd adsorbed to the SAMs of 1 and 3 on Pt than on Au. Previous work indicates that SAMs on Pt are oriented more along the normal to the substrate on Pt than on Au [34], which may facilitate the induced ordering hypothesis and result in increased protein adsorption.…”

Self-Assembled Film Organization in Fast Microcontact Printing Investigated by Sum Frequency Generation Spectroscopy

“…Although gold is a more commonly used substrate in the SAM field, other metals such as platinum have recently been studied for SAM applications with various techniques. 37,[68][69][70][71][72][73][74][75] This preference for Au owes to the fact that Pt substrate is subject to air contamination through oxidation while Au remains rather unchanged. 72,74 Thus, a high initial amount of oxygen leads irremediably to a smaller density of thiols on the surface and has been proved to slow down the rate of thiol binding to the metal lattice.…”

Density functional theory calculations for Pd adsorption on SO4 adsorbed on h-BN

“…The Piranha treatment had been traditionally used to remove organic residues from gold surfaces [9][10][11][12][13][14] and to make self-assembled monolayers (SAMs) of alklthiols (RSH) on metal surfaces [9][10][11][12][13][14][15]. When the SO 4 group stays on the gold surface, it might have a huge effect on generating nano particles on the substrate [7].…”