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Nanoparticle Synthesis and Characterization: A Mechanistic Study of Nanoparticle Morphological Evolution

Grieshaber, Ross (2018) Nanoparticle Synthesis and Characterization: A Mechanistic Study of Nanoparticle Morphological Evolution. Master's Thesis, University of Pittsburgh. (Unpublished)

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The key to designing heterogeneous catalysts for the 21st century is to design them at the nanoscale level with specific morphologies and monodispersity to enhance high product selectivity. This thesis focuses on the synthesis, characterization, and stability of platinum and iron nanoparticles. Control of these nanoparticles monodisperse size and morphology was accomplished through solution phase chemistry. This study has examined two nanoparticle systems to elucidate how of nanoparticle catalysts evolve. The first study focuses on the controlled synthesis of Pt NPs of anisotropic shape and the second study focuses on the carbon encapsulated iron nanoparticle catalysts as they lose morphology.
Platinum nanoparticles have been shown to be quite effective in catalysis technology3–6. The structural dependency of the activity and selectivity of the Pt nanoparticles is significant at sizes below 10 nm. Organic surfactants were used to control their size and dispersion in order to ensure that the nanoparticles remain relatively unchanged and stable.
Shape control of Pt nanoparticles was achieved by the addition of Br- ion during the process of polyol reduction of the Pt ions. Changing the ratio of Br- ions to Pt ions yielded a selective growth of nanocubes, cuboctahedra, truncated octahedral, nanoclusters, and polyhedra with a high-degree of shape monodispersity. These nanoparticles were structurally characterized via transmission electron microscopy to exhibit their local monodispersity of size and morphology.
Iron nanoparticles encapsulated by carbonaceous shells were synthesized by chemical vapor deposition. Transmission electron microscopy (TEM), in situ high resolution scanning electron microscopy, and high resolution transmission electron microscopy (HRTEM SEM/STEM) were used in determine the range of their thermal stability and how the dispersion and morphology of nanoparticles change at elevated temperatures. The carbon encapsulation of the nanoparticles at temperatures below 650 °C. At 650°C, the iron nanoparticles escaped the carbon shells as adatoms and then coalesced in a liquid-like manner. The iron nanoparticles were analyzed in situ and found to undergo particle coalescence and Ostwald digestion at according to nanoparticle diameter, which was attributed to thermal effect and compression of the carbonaceous shell.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Grieshaber, Rossrvg3@pitt.edurvg3
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairYang,
Committee MemberParker,
Committee MemberEnick,
Date: 24 January 2018
Date Type: Publication
Defense Date: 16 November 2017
Approval Date: 24 January 2018
Submission Date: 30 November 2017
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 64
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical and Petroleum Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: nanoparticles, platinum, iron, encapsulation, electron microscopy
Date Deposited: 24 Jan 2018 18:52
Last Modified: 24 Jan 2018 18:52

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