Photochemical Strategies for the Synthesis of Gold Nanoparticles

The synthesis of nanomaterials has received considerable attention in the past few decades owing to the enhanced physical and chemical properties of the particles upon approaching dimensions on the order of the Bohr radius. Several routes have been established for the synthesis of colloidal nanoparticles, where selection of reducing agent and stabilizer along with manipulation of reaction conditions dictate the outcome of the synthetic efficacy. In this work, a number of tactics have been examined in the synthesis of gold nanoparticles, which as a whole can serve as a guideline for the photochemical preparation of various aqueous metal colloids.;Aqueous gold nanoparticles have been synthesized with a variety of photoinitiators such as alpha-hydroxy ketones and alpha-amino ketones through the unimolecular photorelease of free radicals with reducing character. A water-soluble benzoin operated as an excellent precursor and subsequent stabilizer of colloidal gold by its photoproducts. A second technique has operated via an intermolecular pathway for the generation of reducing ketyl radicals from hydrogen atom abstraction involving aromatic ketones with a number of hydrogen donors. Selecting ketones with low-lying triplet states and reactive hydrogen donors led to the facile formation of AuNP in micellar media. Other syntheses of gold nanoparticles have focused on the reactivity of the metal salt itself, such that photolysis of the coordination complex in the vicinity of hydrogen donors has also resulted in efficient gold nanoparticle synthesis. These approaches have been optimized by manipulation of reagent concentrations and photolysis conditions to yield stable colloids with control over particle diameter as well as morphology.;With these strategies in place, the growth of nanoparticles and their surface reactivity were investigated through various methods. In particular, seed-mediated growth and kinetics were established to resolve an autocatalytic mechanism for particle formation. In addition, a novel photochemical seed-mediated growth technique was established for size selective synthesis.;Gold nanoparticles were also derivatized with a series of functional groups to evaluate ligand-nanoparticle interactions, leading the way to possible applications for the materials as optical sensors. Additionally, the photo-releasing synthetic approach has been applied to the design of gold on inorganic supports for heterogeneous catalysis, where preliminary research has revealed their catalytic activity.