Characterisation of nanomaterials: XPS analysis of Core-Shell Nanoparticles

Different approaches to quantify shell thicknesses are presented and compared. These comprise: (1) The infinitesimal columns model (IC), (2) Shard’s empirical formula (TNP-model) and (3) SESSA (Simulation of Electron Spectra for Surface Analysis) simulations with and (4) without elastic scattering. Experimental data on of a round robin experiment of PMMA@PTFE CSNPs were analysed with the aforementioned approaches and show a good mutual consistency and agree with the nominal shell thickness. However, use of the F1s signal leads to significant deviations. Transmission Electron Microscopy measurements revealed that the core-shell structure is non-ideal, i.e. the particles are aspherical and the cores are acentric within the particles. SESSA simulations were employed to estimate the effect of various types of deviations of ideal NPs on the outcome of shell thickness determination. The usefulness and importance of different kind of electron beam techniques for CSNP analysis and in particular shell thickness determination is discussed.