Title page for ETD etd-08042011-202452


Type of Document Dissertation
Author Chang, Xiaojun
Author's Email Address changx@vt.edu
URN etd-08042011-202452
Title Spectral and Physicochemical Characteristics of nC60 in Aqueous Solutions
Degree PhD
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Vikesland, Peter J. Committee Chair
Little, John C. Committee Member
Marr, Linsey C. Committee Member
Morris, John R. Committee Member
Keywords
  • Fullerene nanoparticles (nC60)
  • UV-Vis spectra
  • carboxylic acids
  • extinction coefficient
  • citrate
Date of Defense 2011-07-21
Availability unrestricted
Abstract
Despite its extremely low solubility in water, fullerite C60 can form colloidally stable aqueous suspensions containing nanoscale C60 particles (nC60) when it is subject to contact with water. nC60 is the primary fullerene form following its release to the environment. The aim of the present study was to provide fundamental insights into the properties and environmental impacts of nC60. nC60 suspensions containing negatively charged and heterogeneous nanoparticles were produced via extended mixing in the presence and absence of citrate and other carboxylates. These low-molecular weight acids were employed as simple surrogates of natural organic matter. The properties of nC60 were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and UV-Vis spectroscopy. nC60 produced in the presence of carboxylate differs from that produced in water alone (aq/nC60) with respect to surface charge, average particle size, interfacial properties, and UV-Vis spectroscopic characteristics. Importantly, regularly shaped (spheres, triangles, squares, and nano-rods) nC60 nanoparticles were observed in carboxylate solutions, but not in water alone. This observation indicates that a carboxylate-mediated ‘bottom-up’ process occurs in the presence of carboxylates. Changes in the UV-Vis spectra over time indicate that reactions between C60 and water or other constituents in water never stop, potentially leading to significant morphologic changes during storage or as a result of simple dilution. These results suggest that studies examining the transport, fate, and environmental impacts of nC60 should take the constituents of natural waters into consideration and that careful examination on the properties of the tested nC60 should be conducted prior to and during each study.
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