Determining shell thicknesses in stabilised CdSe@ZnS core-shell nanoparticles by quantitative XPS analysis using an Infinitesimal Columns model

A novel Infinitesimal Columns (IC) simulation model is introduced in this study for the quantitative analysis of core-shell nanoparticles (CSNP) by means of XPS, which combines the advantages of existing approaches. The IC model is applied to stabilised Lumidot™ CdSe/ZnS 610 CSNP for an extensive investigation of their internal structure, i.e. calculation of the two shell thicknesses (ZnS and stabiliser) and exploration of deviations from the idealised CSNP composition. The observed discrepancies between different model calculations can be attributed to the presence of excess stabiliser as well as synthesis residues, demonstrating the necessity of sophisticated purification methods. An excellent agreement is found in the comparison of the IC model with established models from the existing literature, the Shard model and the software SESSA.