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Title: Correlation of electron and X-ray spectroscopies in nanoscale systems
Author: Goode, Angela Erin
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The huge growth in nanotechnology brings with it an increasing need for techniques capable of structural and chemical analysis on the nanoscale. Two such techniques are electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and x-ray absorption spectroscopy in the scanning transmission x-ray microscope (STXM-XAS). Despite the different probe-specimen interactions of EELS and XAS, these techniques both excite transitions from core states into unoccupied excited states, providing remarkably similar chemical information, but with different spatial and spectral resolutions, as well as different electron/photon induced damage properties. Due to advances in the fabrication of diffractive x-ray optics, soft x-ray probes in the STXM can now achieve ~15 nm spatial resolution, while the STEM probe can routinely reach sub-nanometre dimensions. At the same time, the spectral performance of EELS is becoming more competitive with the ~0.1 eV resolutions of x-ray instruments, due to the development of monochromators in the electron microscope. While the spatial and spectral performances of these two techniques are continually converging, the gaps which still exist may be bridged by employing a correlative approach. The motivation of this thesis is to apply both STEM-EELS and STXM-XAS to a range of nanoscale systems, and to investigate the benefits and limitations of this correlative approach. In order to understand the biodegradation of carbon nanotubes (CNTs), spectral signatures corresponding to graphitic carbon have been used to map CNT aggregates within the cellular environment. The nature and distribution of functional groups on oxidised CNTs have also been characterised using EELS, and compared to XAS data from the literature. Lastly, wear debris generated from CoCr hip prostheses has been investigated within explanted tissue. For the first time, detailed chemical analysis was performed of debris particles, which were found to be composed of mainly oxidised Cr as well as trace amounts of oxidised Co. Additionally, some nanoparticles were observed to have metallic Co and Cr cores.
Supervisor: Ryan, Mary ; Porter, Alexandra Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available