Use of XPS to Quantify Thickness of Coatings on Nanoparticles

Abstract

XPS and other surface sensitive methods are being increasingly used to extract quantitative information about organic and inorganic coatings and contamination on nanoparticles. The extraction of coating thickness requires information about particle diameter from other measurements, such as electron microscopy, combined with a model that includes the physical processes associated with XPS. Advantages of using XPS include the sensitivity to very thin coatings (or surface contamination) and the ability to extract important information about organic layers. Single particle information from electron microsocpy combined with XPS sensitivity in determining composition make a powerful combination for nanoparticle anlaysis.

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

“…Determination of the thickness of the organic overlayers in the nanometer range using quantitative XPS spectroscopy is well developed for both planar surfaces and nanoparticles. 62 It is based on an analysis of the attenuation of electrons emitted from the underlying substrate by the overlayer and takes into account both the chemical composition and the morphology of the sample. Typically, a layer of nanoparticles is prepared on the substrate and the collected XPS spectrum represents a signal averaged over the heterogeneous surface.…”

Direct Synthesis of H2O2 on Pd Based Catalysts: Modelling the Particle Size Effects and the Promoting Role of Polyvinyl Alcohol

“…The results showed a marked decrease of PVA, after 12 testing cycles, suggesting that the removal of PVA occurs during the reaction cycles. In order to have an estimation of the PVA thickness and change during the testing cycles, the method reported by Baer et al., based on the use of XPS to quantify thickness of coatings on nanoparticles, was used. The average PVA thickness is about 4 nm in the fresh sample, in agreement with Hirai and Yakura .…”

The Effect of Adsorbed Volatile Organic Compounds on an Ultrathin Water Film Measurement

“…In this work, we used XPS data to observe the trend of the adsorbed layer thickness with time. For a two-layer (overlayer and substrate) structure where the overlayer does not produce electrons with the binding energy of interest, i.e., the overlayer does not produce photoelectrons with the binding energy of Au 4f, the thickness (d over ) of the adsorbed VOCs on the gold surface can be estimated from XPS data [25]:…”

“…In this work, we used XPS data to observe the trend of the adsorbed layer thickness with time. For a two-layer (overlayer and substrate) structure where the overlayer does not produce electrons with the binding energy of interest, i.e., the overlayer does not produce photoelectrons with the binding energy of Au 4f, the thickness (dover) of the adsorbed VOCs on the gold surface can be estimated from XPS data [25]: For a thick substrate (dsub >> λ), IXPS, sub can be considered as I∞, the intensity of a thick sublayer without an overlayer. This is the case for our surface as the 50 nm thick gold layer is much greater than the electron attenuation length of Au 4f photoelectrons (3 nm) through gold.…”