Functionalized nanoparticles in aqueous surroundings probed by X-ray photoelectron spectroscopy

In English In this paper we present the first core-level photoelectron spectroscopic study of solid nanoparticles in liquid water. The particles are SiO2-based with an average diameter of 70 nm and functionalized with carboxylic groups. Despite that the sample is very dilute, we show that it is possible to obtain reasonable photoemission signal containing chemical information about both the ligands and the outermost parts of the SiO2-based core of the nanoparticles. We argue that this is due to a significant enrichment of the dispersed particles at the liquid/vapor interface. This proof-of-principle study expands the field of X-ray photoelectron spectroscopy by adding a new, wide and important class of systems that can be studied. (C) 2011 Elsevier B.V. All rights reserved.