Core-Shell Nanoparticles: Synthesis, Design, and Characterization

The design of core/shell nanoparticles is of great interest for a wide range of applications. The primary focus of this dissertation is on the design and optimization of two synthetic routes. The first one is an aqueous reduction method using sodium borohydride and sodium citrate. This method was extended to design two types of core/shell nanoparticles, both of which have many applications in bio-sensing, magnetic resonance imaging, and magnetically guided SERS for the identification of environmental threats. The first, Fe/Ag core/shell nanoparticles were designed using a novel one-pot method by varying the AgNO3 addition time in the system. For example, if AgNO3 is added five minutes after the start of the reaction, the already formed Fe nanoparticles serve as seeds for heterogeneous nucleation and growth of Ag nanoparticles. The result of the synthesis was 50 nanometer spherical particles with a narrow size distribution. The second type, Fe/SiO2/Au core/shell nanoparticles were designed using a two-step method. First, 150 nanometer spherical Fe nanoparticles were synthesized followed by the addition of tetraethylorthosilicate (TEOS). This created a Fe/SiO2 core/shell nanoparticle to which HAuCl3 was added. In both cases, Fe/Ag and Fe/SiO2/Au, the formed nanoparticles were characterized and tested for the application as SERS active materials. The second part of this dissertation work was focused on using the polyol method to design bimetallic Cu/Ni, Fe/FeOx, and Co/C core/shell nanoparticles. In each case, the polyol method provided an easy one-pot reaction to synthesize these novel nanomaterials. The design of the Cu/Ni nanoparticles allowed for further insight into the polyol mechanism by independently investigating the factors that govern the formation of elemental Cu and Ni nanoparticles. By understanding the ability of the polyols to easily prepare metal and metal oxide nanoparticles, we were able to manipulate a one-pot reaction to design an aqueous ferrofluid consisting of Fe/FeOx nanoparticles. These spherical 15 nanometer particles were studied for their potential application as MRI contrast agents. In addition, the aqueous ferrofluid served as a precursor for the design of magnetic/luminescent core/shell nanoparticles. Finally, the polyol method was extended to create Co/C nanoparticles for permanent magnet applications