Date of Award
© 2019 Laela Ezra. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.
Bachelor of Arts
Chemistry & Biochemistry
Kathryn R. Riley
Engineered nanomaterials (ENMs) have been increasingly used for a variety of purposes. Silver nanoparticles (AgNPs) are the most widely-used ENM to date. AgNPs undergo many transformations while in solution and in biologically relevant environments, so the development of techniques to analyze the extent of these transformations is crucial. The transformation of interest for this work is AgNP aggregation. There exist techniques to monitor aggregation of AgNPs and other ENMs (such as scanning electron microscopy) but often these instruments cannot measure aggregation in situ: some cannot monitor aggregation in real-time, and none are suited for fieldwork. Two methods that can characterize AgNP aggregation are particle impact voltammetry (PIV) and UV-Vis spectroscopy. PIV measures the number of electrons transferred by oxidation of an AgNP, providing particle-specific size data. Supplementing this data, UV-Vis data provides information about the bulk AgNP suspension by measuring local surface plasmon resonance (LSPR). Both are relatively inexpensive and transportable methods and thus were selected to be incorporated. These methods were first individually used to characterize AgNP size and population, which was confirmed with dynamic light scattering (DLS) and SEM data. After initial optimization of these methods, a hybrid cell was designed such that PIV and UV-Vis data could be collected simultaneously. This involved creation of a specialized cap and optimization of the collection methods. A sample study was performed to test how the integrated method measured aggregation. Aggregation of AgNPs was induced by increasing electrolyte concentration. Simultaneous collection of PIV and UV-Vis spectra and kinetics data was performed. The spectral data and kinetics data were consistent with expected aggregation trends, while PIV data initially did not show a clear relationship between measured AgNP size and electrolyte concentration. Upon further investigation of the PIV data, a relationship between transient frequency and aggregation rate constants was found. More studies are needed to investigate this further.
Ezra, Laela , '19, "Monitoring Silver Nanoparticle Aggregation In situ by Integrating Particle Impact Voltammetry and UV-Vis Spectroscopy" (2019). Senior Theses, Projects, and Awards. 237.