Harnessing the Metal Carboxylate Decomposition Reaction: From Canonical Nanocrystal Synthesis to Tunable Graphene Coatings

Masterson, Caitlin Marie

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Year:: 2021
Contributor:: Masterson, Caitlin Marie (creator); Colvin, Vicki (Advisor); Chen, Ou (Reader); Robinson, Jerome (Reader); Brown University. Department of Chemistry (sponsor)
Genre:: theses
Subject:: Nanostructured materials; nanofabrication; Chemistry; Nanomaterial; Graphene; Nanocrystals; Magnetic Nanoparticle; Chemistry, Inorganic; Surface chemistry; Colloids; Carboxylic acids; Chemical vapor deposition; Metallic oxides
Extent:: xvi, 131 p.

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Abstract:: The thermal decomposition of metal carboxylates in nonpolar organic solvents is a widely applied method for the synthesis of uniform metal, metal oxide, and composite nanocrystals; however, the molecular processes leading to their formation are not well explored and can result in notable effects on the products. This work examines the deposition of carbonaceous materials on the surfaces of inorganic nanocrystals that may occur during their formation. This phenomenon is a consequence of the evolution of reactive gases that coincide with nanoparticle growth. Changes in reaction conditions – especially temperature and time – impact the nanocrystal products and gaseous byproducts and provide a valuable tool for achieving tailored nanocrystal morphologies. In this work, I demonstrate that iron oxide nanocrystals formed in this canonical reaction can become resistant to further growth and eventual dissolution. This behavior results from surface “fouling” due to carbon deposition and has been observed to occur on transition metal catalyst particles during biofuels production under similar conditions. X-ray diffraction of these products shows reduced iron oxide phases occur along with carbon deposition, and chromatographic analysis of the volatile reaction byproducts identifies CO as a reductant. From this data, I infer a mechanism by which these carbon residues form. Spectroscopic methods show that when synthesized under optimal conditions, these ultrathin carbon coatings resemble graphene, and I demonstrate that the coatings can serve as a barrier to corrosion in a variety of circumstances. Next, I investigate how the reaction parameters can be adjusted to yield graphene-coated iron oxide nanocrystals with tunable thickness. By operating at higher temperatures, the generation of carbon feedstock gases can be increased to produce thicker and higher quality graphene. The iron oxide can subsequently be removed by etching to obtain graphene nanoflakes. This method provides a novel technique to synthesize nanoscale carbon allotropes which requires low temperature and energy inputs compared to conventional methods. The universality of this approach, which I refer to as liquid phase chemical vapor deposition (LP-CVD), is demonstrated with a similar synthesis for manganese oxide, suggesting that the strategy can be applied widely to high temperature syntheses of transition metals and their oxides.
Notes:: Thesis (Ph. D.)--Brown University, 2021

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Citation

Masterson, Caitlin Marie, "Harnessing the Metal Carboxylate Decomposition Reaction: From Canonical Nanocrystal Synthesis to Tunable Graphene Coatings" (2021). Chemistry Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:jqee6hr4/

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Chemistry Theses and Dissertations

Theses and Dissertations for the Chemistry department.
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