Noble metal nanoparticles (NPs) have shown promise as imaging agents, drug delivery platforms, and plasmonic sensors. Anisotropic gold NPs, such as gold nanostars, have particularly received attention due to their shape-dependent optical and spectral properties. With their 3D anisotropic structure with branches protruding into different directions and high surface areas, gold nanostars have been used as single-particle orientation sensors under optical microscopy, drug delivery platforms, and plasmonic nanocathodes with tunable spatiotemporal current control. Fundamental understanding of the relationship between the localized surface plasmon resonance wavelength of AuNS and the imaging wavelength, NP shape-effects during ligand-receptor interactions, and their growth mechanisms during seedless growth, however, are still lacking. This dissertation presents the use of gold nanostars as optical probes under differential interference contrast (DIC) microscopy and drug-delivery platforms. Due to their wavelength and angle-dependent optical patterns, anisotropic gold nanostars can function as orientation-sensors under DIC microscopy. Via finite-difference time-domain simulation method, we have shown that when the imaging wavelength is changed from below to above the plasmon resonance of an anisotropic nanoparticle, DIC patterns inverted from dark to bright or bright to dark due to the reversal in the electric field direction depending on the wavelength relative to the nanoparticle plasmon resonance. Furthermore, due to their orientation-dependent optical patterns, nanostars were used as simultaneous single-particle drug carriers and optical probes under DIC microscopy to investigate the effect of nanoparticle core shape during targeted ligand-receptor interactions. We have shown that aptamer conjugated nanostars and nanospheres show different translational dynamics on the cell membrane overexpressed with target receptors, potentially due to the multivalent interactions offered by different tips from the gold nanostars. Lastly, by using electron tomography, we constructed growth maps of gold nanostars synthesized with three different Good’s buffers, highlighting the importance of initial nucleation in determining the final morphology of nanoparticles during seedless growth. By taking advantage of the plasmonic material and the 3D anisotropy offered by gold nanostars, use of single-particle plasmonic platforms for biological, chemical, and nanophotonic applications has been demonstrated.

Creator

• Choo, Priscilla

DOI

• https://doi.org/10.21985/n2-ar67-7a57

Subject

• Chemistry

Language

• en

Alternate Identifier

• etdadmin_upload_837616
• http://dissertations.umi.com/northwestern:15668

Keyword

• Nanoparticle
• Nanostar
• Electron Tomography
• DIC Microscopy

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright