|AVS 57th International Symposium & Exhibition|
|Applied Surface Science||Wednesday Sessions|
|Session:||Surface Mass Spectrometry: SIMS and Beyond|
|Presenter:||J.L.S. Lee, National Physical Laboratory, UK|
|Authors:||J.L.S. Lee, National Physical Laboratory, UK
I.S. Gilmore, National Physical Laboratory, UK
D.C. Cox, National Physical Laboratory, UK
M.P. Seah, National Physical Laboratory, UK
S.J. Spencer, National Physical Laboratory, UK
|Correspondent:||Click to Email|
Nanoparticles are front-runner nanotechnologies key to high innovation products, such as biodiagnostics, drug delivery, medical imaging (contrast agents), cosmetics, sunscreens and catalysts. The surface and bulk chemistries of nanoparticles are crucial for their unique properties. There is also increasing concern over the potential health, environmental and safety risks of nanomaterials. Robust and consistent methodologies for characterising nanoparticle surface and bulk chemistries are urgently needed to support standardisation, regulatory requirements and toxicology studies .
Secondary ion mass spectrometry (SIMS) has been applied in nanoparticle characterisation [2,3]. However, the fundamentals of the sputtering of nanoparticles are not yet well understood. The sputtering yield is expected to be significantly different for nanoparticles compared to bulk materials, due to the dimension of nanoparticles being similar to the size of the SIMS collision cascade, and the larger available surface area for secondary emission. In this study, SIMS depth profiles were obtained for model Au nanoparticles, with diameters ranging from 10 nm – 100 nm, dispersed and mounted onto a silanised silicon substrate. The sputtering yields and profile shapes are evaluated for both atomic and cluster primary ion beams (Ar+, Bi+, Bi3+ and C60n+), using a range of primary ion energies. The nanoparticles are characterised by SEM and AFM both before and after sputtering. There is a significant increase in the sputtering yield for nanoparticles compared with bulk materials, in agreement with predictions from a recent molecular dynamics study . In addition, for the first time, we observed the sputtering of nanoparticles in real time using a focused ion beam system with simultaneous SEM imaging. This provides valuable information for interpreting the SIMS depth profiles of nanoparticles and an interesting phenomenon of nanoparticle coalescence was observed. These results contribute towards developing the essential underpinning metrology and providing a practical procedure to analysts for the chemical characterisation and compositional depth profiling of nanoparticles.
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