Author's School

School of Engineering & Applied Science

Author's Department/Program

Biomedical Engineering

Language

English (en)

Date of Award

5-24-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Younan Xia

Abstract

In the first part of my dissertation, I developed two approaches for selectively probing the SERS activities of individual hot spots, i.e., experimentally detect the SERS signals only for the molecules that are trapped within the hot-spot region in individual Ag nanoparticle dimers. Then, I performed a systematic investigation on the SERS activity of individual dimers composed of two closed spaced Ag nanoparticles. By utilizing Ag nanoparticles displaying a variety of well-defined shapes, sizes and orientations to construct the dimers, I were able to precisely correlate the detected SERS signals to the specific geometry of individual hot spots. In the second part of this dissertation, I performed a systematic investigation on the galvanic replacement reaction between PtCl62- and Pd nanocrystals with well-defined shapes including octahedra, nanocubes, and nanorods. The resultant hollow Pd-Pt bimetallic nanostructures were employed as electrocatalysts for the oxygen reduction reaction: ORR). Our results demonstrated that the nanostructures derived from Pd octahedra displayed the highest ORR activity, being 1.7 times more active based on equivalent Pt mass than the commercial Pt/C. I also conducted a mechanistic study on the galvanic replacement reaction between AuCl4- and Pd nanorods. Differently from the Pd-Pt system, a new type of hybrid nanostructure in the tadpole shape consisting of a Au head and a Pd tail was obtained due to a localized galvanic replacement mechanism. As an extension of my work to develop new electrocatalysts for the ORR, a template-engaged reaction was utilized for the synthesis of RuSe2+ nanotubes. The RuSe2 nanotubes were active towards the ORR and displayed no loss in activity in the presence of methanol, as opposed to commercial Pt/C. Finally, the template-engaged reaction was applied to the synthesis of Se@MSe: M = Zn, Cd or Pb) colloidal spheres having similar sizes but different compositions. They were utilized as building blocks to obtain 3D photonic crystals via self-assembly. Moreover, superparagametic properties could be obtained via the incorporation of Fe3O4 nanoparticles into the a-Se cores. Taken together, this represents a versatile approach to the synthesis of magnetoactive spheres with similar dimensions but a variety of compositions and properties.

Comments

Permanent URL: http://dx.doi.org/10.7936/K7MK69WB

Download

Share

COinS