Chan, Yang-Hsiang (2010-05). Applications of Self-assembly for Molecular Electronics, Plasmon Coupling, and Ion Sensing. Doctoral Dissertation. | Thesis individual record

This dissertation focused on the applications of self-assembled monolayers
(SAMs) technique for the investigation of molecule based electronics, plasmon coupling
between CdSe quantum dots and metal nanoparticles (MNPs), and copper ion detection
using enhanced emission of CdSe quantum dots (QDs). The SAMs technique provides
an approach to establish a robust, two-dimensional and densely packed structure which
can be formed on metal or semiconductor surfaces. This allows for the design of
molecular assemblies that can be used to understand the details of molecular conduction
by employing various electrical testbeds. In this work, the strategy of molecular
assemblies was used to pattern metal nanoparticles on GaAs surfaces, thereby furnishing
a platform to explore the interactions between QDs and MNPs. The enhanced emission
of CdSe QDs by MNPs was then used as a probe for ultrasensitive, cheap, and rapid
copper(II) detection.
The study is divided into three main facets. The first one aimed at controlling
electron transport behavior through porphyrins on surfaces with an eye toward
optoelectronic and light harvesting applications. The binding of the porphyrin molecules to Au surfaces, pre-covered with a dodecanethiol matrix, was characterized by FTIR,
XPS, AFM, STM, of. This study has shown that the perfluoro coupling group between
the porphyrin macrocycle and the thiol tether may provide a means of controlling the
tunneling behavior.
The second area of this study focused on the design of a simple platform to
examine the coupling between metal nanostructures and quantum dot assemblies. Here
we demonstrate that by using a patterned array of Au or Ag nanoparticles on GaAs,
plasmon enhanced photoluminescence (PL) can be directly measured and quantified by
direct scaling of regions with and without metal nanostructures.
The third field presented a simple manner for using the enhanced PL of CdSe
QDs as a probe for ultrasensitive Cu2+ ion detection and quantitative analysis. The PL of
QDs was enhanced by two processes: first, photobrightening of the material, and second,
plasmonic enhancement by coupling with Ag nanoprisms. This strong PL leads to a high
sensitivity of the QDs over a wide dynamic range for Cu2+ detection, as Cu2+ efficiently
quenches the QD emission.

etd chair
publication date