Curvature driven phase separation in mixed ligand coated gold nanoparticles
Name
71229905-MIT.pdf
Description
Full printable version
Size
1.58 MB
Format
Adobe PDF
Checksum (MD5)
91b28e1b649e0cdbb431fc961c83e34c
Author(s)
Jacob Silva, Paulo H
Advisor(s)
Francesco Stellacci.
Date Issued
2006
Publisher
Massachusetts Institute of Technology
Abstract
Monolayer-coated gold nanoparticles have been the subject of extensive studies in fields ranging from physics to medicine. The properties of these nanomaterials such as solubility and surface energy are often attributed solely to the chemical functionalities of the ligand head-groups. However, the morphology of these monomolecular layers on gold nanoparticles plays as important of a role as the surface chemistry. Intriguing phase-separation phenomena have been observed for mixed self-assembled monolayers (SAM) of octanethiol (OT) and mercaptopropionic acid (MPA) on the surface of gold nanoparticles. These ordered structures are studied here through scanning tunneling microscope (STM) images, as a function of the gold core diameter, which is a measure of the particle's curvature. The packing of OT homoligand nanoparticles is found to have a head-group spacing of 0.54 nm, which differs from that on flat gold (111) surfaces, 0.5 nm. The OT:MPA heteroligand nanoparticles are observed to phase-separate into ordered ribbon-like domains, with spacings that depend on the nanoparticle diameter. A geometric framework that includes a continuous and crystallographic description is established to best describe the observed behaviors.
Description
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references (leaves 31-33).
Subjects
Materials Science and Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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