Greener syntheses of metallic nanoparticles and zinc oxide nanopowders.

摘要

In recent years, nanotechnology and nanomaterials synthesis have attracted a great deal of attention in the scientific community. Nanomaterials display size and morphology-related optical properties that differ from their bulk counterparts and therefore can be used for many applications in different fields such as biomedicine, electronics, antibacterial agents, and energy. Attempts to fabricate different morphologies of metallic and metal oxide nanoparticles (NPs) have successfully yielded attractive nanostructures such as particles, rods, helices, combs, tetra-pods, and flowers, all displaying properties mainly related to their enhanced surface area and/or aspect ratios. Most of the above mentioned nanomaterials productions have employed harsh synthetic routes such as high temperatures, low pressures, and the use of costly equipments. Here we show how a greener approach to nanomaterials synthesis is feasible with both minimization of aqueous precursors, energy and employment of a multi-block heater for temperature control.;We present in this thesis several methods for the preparation of NPs of several materials that focus on minimizing the environmental impact of the synthesis itself. First, we describe the use of the toroidal form of plasmid DNA as a rigid narrowly dispersed bio-polymeric nanocavity, which mold the formation of disc-shaped nanoparticles of several types of metals. This approach exploits several properties of plasmid DNA: (a) DNA affinity for metal cations, (b) toroidal plasmid DNA structures which are favored by metal ionic binding, and (c) the ability to vary plasmid size. Herein, we present a complementary synthetic method based on a kinetic approach wherein the plasmid DNA acts as a template to initiate and control the formation of Au and other metallic NPs by incubation at elevated temperatures.;Also reported herein is a simple, scalable hydrothermal method to make ZnO NPs that exploits temperature to precisely control the range of pH values of an organic amine buffer. The presence or absence of ethylenediaminetetraacetic acid in the tris(hydroxymethyl)aminomethane buffer further modulates the morphology of the ZnO nanomaterials since both compounds can serve as nucleating sites, and as stabilizing agents that prevents agglomeration.