Quantification of the Shell Thickness of Tin Oxide/Gold Core–Shell Nanoparticles by X-ray Photoelectron Spectroscopy

Abstract

Encapsulation of nanoparticles (NP) by a shell material provides characteristics and properties not achievable by the individual materials of the core and the shell. Therefore, the characterization of morphology parameters of core–shell nanoparticles (CSNP) is critical to determine their performance. In this work, an analysis to determine the shell thickness of CSNP has been conducted using a simple and noniterative procedure known as Shard’s methodology, where the conversion of XPS peak intensities into shell thickness can be performed. Implementing the Simulation of Electron Spectra for Surface Analysis (SESSA), we acquired an insight into the morphology and composition of the CSNP by simulating the spectra from XPS to extract the parameters (Shard’s methodology) and confirm the core–shell ratio with experimental spectra to quantify the shell thickness. The CSNPs were synthesized with reverse micelle templating using diblock copolymer micellar templates, using various ratios of tin and gold precursors to form SnO2@Au core–shell nanoparticles. Considering elastic-scattering effects, a good agreement was found in the quantification of the shell thicknesses with a variation inside the ±10% regime of the effective attenuation length (EAL). This work demonstrates the use of simulation software as a complementary tool to a multitechnique analysis for a detailed understanding of CSNP.