| AVS 63rd International Symposium & Exhibition | |
| Applied Surface Science | Thursday Sessions |
| Session AS-ThA |
| Session: | Advances for Complicated Sample Preparation Strategies and Complex Systems |
| Presenter: | Caterina Minelli, National Physical Laboratory (NPL), UK |
| Correspondent: | Click to Email |
Reliable and reproducible measurement methods for nanoparticles will significantly impact the uptake of these materials in commercial applications and allow industry to comply with regulation. However, there are significant challenges in the analysis of nanomaterials due to, among other factors, the interdisciplinary nature of the field, the lack of adequate reference materials to calibrate analytical tools and the difficulties associated both with sample preparation for analysis and the interpretation of data. Furthermore, the inconclusive outcomes of nanoparticle toxicity risk assessments can largely be traced to a failure to address these measurement challenges.
The preparation of nanoparticle samples for analysis can significantly alter both the nanoparticles themselves and the results of the analysis. Measuring colloidal nanoparticles using vacuum-based techniques is particularly prone to artefacts and irreproducibility introduced by sample preparation. In order to produce relevant and meaningful data from nanoparticle analysis it is therefore important to establish sound sample preparation protocols. It is good practice to use a combination of techniques which can be employed directly to the colloidal suspension and on the dried particles to ensure a meaningful interpretation. Examples which will be discussed include the measurement of the density of polymeric nanoparticles by small angle X-ray scattering (SAXS) and analytical centrifugation, and the analysis of the protein coatings on gold nanoparticles in liquid media (in-situ) and ex-situ with high vacuum techniques such as X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). The challenges in sample preparation for these methods and the difficulties of data interpretation will be described in detail. The in-situ measurement of nanomaterials in complex matrices is highly sought after by industry and regulatory bodies, but remains an unmet challenge. The potential application of new methods, such as non-linear optical techniques, will be considered.
Inter-laboratory studies enable the refinement of sample preparation protocols, which in turn have a positive impact on the broader adoption of the analytical method for nanoparticle characterisation. We will discuss the main outcomes of a VAMAS inter-laboratory study whose aims included to assess the inter-laboratory variability in the measurement of nanoparticle coatings using XPS and LEIS and identify sources of variability in sample preparation procedures. This work will directly input into ongoing efforts in ISO TC201 to standardize the surface chemical analysis of nanoparticles.