Graduation Year

2006

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Electrical Engineering

Major Professor

Stephen Saddow, Ph.D.

Keywords

Nanocrystal, Biomarker, Nanotechnology, Bioconjugation, Tag

Abstract

Recent advancements in nanotechnology create a need for a better understanding of the underlying physical processes that lead to the different behavior of nanoscale structures in comparison to bulk materials. The influence of the surrounding environment on the physical and optical properties of nanoscale objects embedded inside them is of particular interest. This research is focused on the optical properties of semiconductor quantum dots which are zero-dimensional nanostructures. There are many investigation techniques for measuring the local parameters and structural characteristics of Quantum Dot structures. They include X-ray diffraction, Transmission Electron Microscopy, Wavelength Dispersive Spectroscopy, etc. However, none of these is suitable for the study of large areas of quantum dots matrices and substrates. The existence of spatial inhomogeneity in the quantum dots allows for a deeper and better understanding of underlying physical processes responsible in part

icular for the observed changes in photoluminescence (PL) characteristics. Spectroscopic PL mapping can reveal areas of improved laser performance of InAs/InGaAs quantum dots structures. Establishing physical mechanisms responsible for two different types of spatial PL inhomogeneity in InAs/InGaAs quantum dots structures for laser applications was the first objective of this research. Most of the bio-applications of semiconductor quantum dots utilize their superior optical properties over organic fluorophores. Therefore, optimization of QD labeling performance with biomolecule attachment was another focus of this research. Semiconductor quantum dots suspended in liquids were investigated, especially the influence of surrounding molecules that may be attached or bio-conjugated to the quantum dots for specific use in biological reactions on the photoluminescence spectrum. Provision of underlying physical mechanisms of optical property instability of CdSe/ZnS quantum dots used for biologi

cal applications was in the scope of this research. Bioconjugationand functionalization are the fundamental issues for bio-marker tagging application of semiconductor quantum dots. It was discovered that spatially resolved photoluminescence spectroscopy and PL photo-degradation kinetics can confirm the bioconjugation. Development of a methodology that will allow the spectroscopic confirmation of bio-conjugation of quantum dot fluorescent tags and optimization of their performance was the final goal for this research project.

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