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Correlated electron microscopy with electro-optical imaging of hexagonal tungsten oxide nanorods

Date

2019

Authors

Cashen, Christina J., author
Sambur, Justin B., advisor
Prieto, Amy, committee member
Li, Yan Vivian, committee member

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Abstract

Fundamental understanding of the dynamics of ion insertion into a host material are essential to accommodate the rising demand for energy storage technology. It has been established that single nanoparticle electrodes greatly improve the kinetics of the ion insertion reaction, however the heterogeneous behavior of single particles correlated to the structure of the particle has been challenging to determine. This work takes on this challenge by developing a method that implements optical microscopy to study the optical modulations of electrochromic single particle hexagonal tungsten oxide (h-WO3) nanorods with transmission electron microscopy (TEM). Heightened resolution provided by TEM reveals sub-atomic structural details which would be impossible to observe with other techniques. This work introduces a method of measuring correlated single particle optical activity of WO3 with TEM resolution images of the same particle. This study found heterogeneous optical modulations of the carbon film considerably influenced the optical activity of WO3. Bearing in mind this behavior is vital for future experiments using this method. After this is accounted, we compare the optical activity of two single particles using the common parameters: maximum optical density (max OD) and the time it takes to reach 90% of the max OD (t90). This comparison provides further evidence that the presence of nanosized step-edge gradients contribute to the ion insertion dynamics of this electrochromic host material. Further study using this method can reveal a understanding of how the presence of step-edges contributes to the local lattice dynamics upon lithiation of a nanorod.

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