Strategies for the Thermal and Photochemical Modification of Gold Nanoparticles (AuNPs) and the Fabrication of AuNP Hybrid Materials

Among the existing approaches for the functionalization of the gold nanoparticle (AuNP), a direct interfacial organic reaction of terminal functional groups exposed on the surface of template nanoparticles with various reactants has been shown as a promising strategy to incorporate desired functionality onto the AuNP monolayer. In our own attempts to extend the types of reactions that can be utilized for efficient interfacial modifications of AuNPs, we examined uncatalyzed Huisgen 1,3-dipolar click-type cycloaddition of azide-modified AuNPs to terminal alkynes. These particular reactions were found to be generally too slow to be useful at ambient temperatures but it was shown that high pressure conditions (11 000 atm) can be used as an efficient tool to facilitate these reactions on the AuNPs with high yields and with no detrimental effects on the gold core. Photochemical reactions of suitably functionalized gold nanoparticles (AuNPs) can also be utilized to chemically modify AuNPs under mild conditions, given that photoinitiated reactions don’t require high temperature or catalysis. Diazirine, as an excellent carbene precursor, readily generates the reactive carbene intermediate by photoinitiated nitrogen extrusion. In Chapter Three, the synthesis and characterization of diazirine-modified AuNPs are described and it is demonstrated that upon irradiation, intermediate carbene-modified AuNPs are formed and that their subsequent insertion reactions with trapping reagents lead to interfacial modification of the diazirine-modified AuNPs. Furthermore, I show that photo-generation of a carbene on the monolayer of AuNPs in the presence of host materials drives the formation of covalently assembled AuNP-based hybrid materials via carbene insertion/addition reactions. Diazirine-modified AuNPs with different sizes were prepared and irradiated in the presence of a series of substrates including CNTs, diamond, graphene, and glass slide. Upon UV irradiation of diazirines attached onto the AuNPs, intermediate carbenes were generated and the following carbene insertion/addition reactions could occur with the surface functionality of substrates. Using this method, we prepared hybrids including AuNP-CNT, AuNP-Diamond, AuNP-Graphene, and AuNP-Glass. In total, this thesis work reviews my efforts toward chemical modification of AuNPs via thermal and photothermal interfacial reactions. Moreover, it provides an efficient strategy for the synthesis of covalently assembled AuNP-based hybrid materials employing carbene insertion/addition reactions