Measure coating thickness on nanoparticles
The JRC, in collaboration with 20 international laboratories, supported a Versailles Project on Advanced Materials and Standards (VAMAS) study on the measurement of the shell thickness and chemistry of nanoparticle coatings X-ray Photoemission Spectroscopy (XPS) and Low Energy Ion Scattering techniques.
Engineered nanoparticles are of major importance in novel technologies for e.g. medical diagnostics, sensors, drug delivery vehicles. Their utility is constrained by the fine tolerances required for size, shape, and ability to interact with other functional elements. The characterisation of surface chemistry, coating composition and thickness of engineered nanoparticles are amongst the most challenging physico-chemical properties to obtain because quantitative measurements are difficult to perform in-situ and require the use of specialized instruments that are not widely available or easy to use and understand.
The collaborative study, organized by the UK National Physical Laboratory had two main objectives: (i) Compare the results from different laboratories when analysing common samples and (ii) Determine the most significant challenges in performing these analyses, to assess their significance and to identify actions to ameliorate the most important of these.
The results have shown that following careful analysis of samples prepared by a common method and using a common data analysis approach agreement on shell thickness and composition using XPS was approximately 10%. A similar level of agreement between participants using LEIS to measure shell thickness was also obtained, and was also in reasonable agreement with the mean XPS thickness. Furthermore several important challenges such as the importance of appropriate documentation and controls describing preparation methods and sample history were also identified.