The influence of sample preparation on XPS quantification of oxygen-functionalised graphene nanoplatelets

X-ray photoelectron spectroscopy (XPS) is widely used for characterising the chemistry of graphene-related two-dimensional materials (GR2M), however the careful preparation of the sample for analysis is important in obtaining representative quantifications. We report an investigation by three laboratories showing that the preparation method for oxygen-functionalised graphene nanoplatelet (GNP) powders has a significant effect on the homogeneous-equivalent elemental composition measured in XPS. We show that pressing GNP powders onto adhesive tapes, into recesses, or into solid pellets results in inconsistencies in the XPS quantification. The measured oxygen-to-carbon atomic ratio from GNP pellets depends upon the die pressure used to form them and the morphology of the GNPs themselves. We recommend that powder samples of GR2Ms are pelletised prior to XPS analysis to improve repeatability and reproducibility of measurements.

Automated summary

X-ray photoelectron spectroscopy (XPS) is commonly used for characterizing the chemistry of graphene-related two-dimensional materials (GR2M). However, the sample preparation method has a significant impact on the quantification results in XPS analysis. An investigation by three laboratories reveals that the preparation of oxygen-functionalized graphene nanoplatelet (GNP) powders affects the measured elemental composition in XPS. Pressing GNP powders onto adhesive tapes, into recesses, or into solid pellets leads to inconsistencies in the XPS quantification. The study recommends pelletizing powder samples of GR2Ms before XPS analysis to improve the repeatability and reproducibility of measurements.