X-ray spectro-microscopy provides quantitative chemical information similar to electron energy-loss spectroscopy (EELS), but at different spatial and spectral resolutions and penetration length into the sample. The relaxed thickness constraint of X-ray microscopy also offers exciting opportunities for spectro-microscopy of samples in liquids. Here we present X-ray microscopy (XM) studies of in situ nanoparticle growth and corrosion. Dynamic X-ray experiments are correlated with electron microscopy analysis of ex situ samples to provide structural and/or chemical information at higher spatial resolution.

Figure 1 shows a custom-built electrochemical cell which has been developed to allow real-time imaging of the growth of ZnO nanostructures [1]. This method allows us to directly observe transient events which occur during electrodeposition such as instantaneous versus delayed nucleation, providing insights into the growth mechanisms of electrodeposited ZnO. The X-ray microscope provides information with ~30 nm spatial resolution; this data is then correlated to subsequent ex situ morphological analysis in the scanning electron microscope.

These techniques have then been applied to the corrosion of nanoscale wear debris from cobalt-chromium-molybdenum metal-on-metal (MOM) hip prostheses. The wear debris has been implicated in the eventual failure of MOM hips. EELS and XM analysis of explanted tissue from patients with failed hip prostheses reveals debris that is rich in octahedrally coordinated Cr³⁺ and Co-deficient. However, the mechanism for cobalt loss is not understood. Using adapted electrochemical cells to simulate oxidative biological environments, the response of CoCrMo nanoparticles is investigated by in situ XM, revealing the conditions under which Co is leached from the wear debris.

[1] SER Tay et al, Nanoscale 8 (2016)  p1849

Figures:

Figure 1. (A) Custom-built in situ wet cell which allows nanoparticle samples to be imaged by TXM, in liquids and under electrochemical control. (B) TXM images showing the evolution of ZnO nanorod and nanoplate morphology with increasing electrodeposition time. Image dimensions are 13 × 13 μm.

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EMC Abstracts - https://emc-proceedings.com/abstract/dynamic-spectro-microscopy-of-nanoparticle-growth-and-corrosion/