Surface Functionalized Gold Nanoparticle Applications in Catalysis and Lipid-Nanoparticle Assemblies

The general objectives of my dissertation are to devise strategies to impart unique functionality to gold nanoparticles (AuNPs) through surface modification and utilizing such surface-functionalized AuNP systems to 1) facilitate colloidal catalyst recovery and reuse while maintaining activity and 2) measure the interactions of engineered AuNPs with biological membranes as related to stimuli-responsive liposomal therapeutics. AuNP surface functionalization is an essential step in the synthesis, stability and functionality-specific applications of AuNPs. Due to the ability to control AuNP shape, size and surface properties, AuNP applications have seen an exponential growth in various sectors that include catalysis, biomedicine, drug-delivery, sensing, imaging, energy applications, etc. Solution-based synthesis of surface functionalized AuNPs through the Turkevich and Brust synthesis methods produce reproducible narrow size-distribution colloidal AuNPs and provides a reliable platform to investigate effects of surface functionality on various applications. Chapters 1 and 2 introduces the concept of AuNP as catalyst and experimentally compares the two major categories of catalyst; colloidal versus supported catalyst). Chapters 3-4 shows the successful development of a platform of colloidal AuNPs which are recovered from an aqueous medium through pH manipulation and illustrates how ligand structure on the AuNP surface is a primary factor determining catalytic activity, stability and recoverability. Chapter 5 is aimed at investigating interactions of engineered AuNP with the lipid membranes of small unilamellar vesicles (SUV) and depicts substantial membrane softening from AuNP inclusions. The colloidal systems were investigated through various characterization tools such as calorimetry, light scattering, spectroscopy and advanced electron microscopy. Additionally, this work has employed elastic and inelastic neutron scattering techniques heavily as a result of extensive collaboration with government user facilities such as National Institute of Standards and Technology and Oak Ridge National Laboratory. Overall, in my doctoral research, I have successfully manipulated AuNP properties through surface functionalization and assessed AuNP applications in two major areas: (1) sustainable catalysis and (2) lipid-nanoparticle assemblies as a platform to quantify membrane biomechanical properties. The current work sets the groundwork for expansion of such functionalized nanoparticle systems (including other metal NPs such as Pt, Pd, Ag, etc.) to a much larger application base in catalysis, nano-bio interactions, nanomedicine, drug delivery, and sensors to name a few