In situ photoelectron spectroscopy study of water adsorption on model biomaterial surfaces

Using in situ photoelectron spectroscopy at near ambient conditions, we compare the interaction of water with four different model biomaterial surfaces: self-assembled thiol monolayers on Au(111) that are functionalized with methyl, hydroxyl, and carboxyl groups, and phosphatidylcholine (POPC) lipid films on silicon. We show that the interaction of water with biomaterial surfaces is mediated by polar functional groups that interact strongly with water molecules through hydrogen bonding, resulting in adsorption of 0.2-0.3 ML water on the polar thiol films in 700 mTorr water pressure and resulting in characteristic N 1s and P 2p shifts for the POPC films. Provided that beam damage is carefully controlled, in situ electron spectroscopy can give valuable information about water adsorption which is not accessible under ultrahigh vacuum conditions.This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division and Materials Sciences Division of the US Department of Energy, under contracts DE-AC03-76SF00098 and DE-AC02-05CH11231. Part of the work was performed at the Molecular Foundry. GK thanks the Max Planck Society for financial support