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Peptide-Based Molecular Transformations for Tuning the Structure and Properties of Chiral Gold Nanoparticle Single Helices

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 (Unpublished)

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Abstract

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.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Punekar, Soumitra Mokashisop23@pitt.edusop230000-0002-4322-4421
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairRosi, Nathanielnrosi@pitt.edunrosi
Committee MemberLiu, Haitaohliu@pitt.eduhliu
Committee MemberChilders, W. Sethwschild@pitt.eduwschild
Committee MemberWalsh, Tiffanytiffany.walsh@deakin.edu.au
Date: 25 September 2019
Date Type: Publication
Defense Date: 29 July 2019
Approval Date: 25 September 2019
Submission Date: 1 July 2019
Access Restriction: 2 year -- Restrict access to University of Pittsburgh for a period of 2 years.
Number of Pages: 175
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Plasmonic chirality, Peptide assembly, Helical gold nanoassemblies
Date Deposited: 25 Sep 2019 15:02
Last Modified: 25 Sep 2019 15:02
URI: http://d-scholarship.pitt.edu/id/eprint/36998

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