relation: http://d-scholarship-dev.library.pitt.edu/36998/
title: Peptide-Based Molecular Transformations for Tuning the Structure and Properties of Chiral Gold Nanoparticle Single Helices
creator: Punekar, Soumitra Mokashi
description: Helical gold nanoparticle (AuNP) superstructures have generated tremendous research interest due to wide-ranging applications in metamaterial optics, chiral sensing, detection, and several other fields. These optical materials consist of plasmonic AuNPs arranged in a helical topology, giving rise to unique chiroptical properties that depend on the structural parameters of the helix. This dissertation describes advances in systematically modulating the structural features and consequently adjusting the chiroptical properties of single-helical AuNP superstructures. The modifications to the single-helical nanoscale architecture are achieved via small molecular transformations within a gold-binding peptide assembly agent, and in one case, addition of external additives.  Specifically, in Chapter 2, I present a rational strategy to adjust the helical pitch of AuNP single helices by tuning the aliphatic tail length within a family of peptide conjugate molecules. I demonstrate that the helical pitch increases and the chiroptical signal intensity decreases with an increase in aliphatic tail length. In Chapter 3, I focus on the N-terminus amino acid segment within the peptide sequence as means of further adjusting assembly metrics and helical pitch length. Via a single amino acid mutation within a class of peptide conjugates, I achieve an overall decrease in the average helical pitch of single-helical superstructures. Chapter 4 describes the adjustment of particle size within single-helical superstructures by tuning peptide-NP interaction via C-terminus peptide sequence modification. Key amino acid-NP interactions are identified, via theoretical simulations, that ultimately affect the size of component particles within helical superstructures. These molecular alterations yield single helices comprising larger particles that exhibit intense chiroptical signal. Finally, in Chapter 5, I screen a series of cetyltrimethylammonium bromide (CTAB) analogs to control the shape of constituent particles within helical superstructures. I outline selection criteria (CTAB tail length and concentration) necessary for the deliberate conversion of small particles within the single-helical superstructures to anisotropic (prisms and polygonal) particles.  Overall, the advances presented in this dissertation highlight multiple levels of control over the nanoscale architecture and properties of one particular type of chiral superstructures. This is a significant step in constructing designed chiral NP assemblies which are essential for serving myriad potential applications.
date: 2019-09-25
type: University of Pittsburgh ETD
type: PeerReviewed
format: application/pdf
language: en
identifier: http://d-scholarship-dev.library.pitt.edu/36998/1/Punekar_ETD_Pitt2019.pdf
identifier:   Punekar, Soumitra Mokashi  (2019) Peptide-Based Molecular Transformations for Tuning the Structure and Properties of Chiral Gold Nanoparticle Single Helices.  Doctoral Dissertation, University of Pittsburgh.    (Unpublished)