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|Title: ||Analyte sensing with luminescent quantum dots.|
|Authors: ||Mulrooney, Ray|
|Supervisors: ||Callan, John F.|
|Issue Date: ||2009|
|Publisher: ||The Robert Gordon University|
|Abstract: ||Semiconducting nanocrystals otherwise known as Quantum Dots
(QDs) have attracted considerable attention over the last number of years
due to their unique optical properties and potential applications. Their
narrow size-tunable emission spectra, broad absorption spectra,
resistance to photobleaching and long fluorescent lifetimes make them
ideal for sensing ions and small molecules.
This thesis explores the potential of QDs to function as the emissive
unit in fluorescent probes. Primarily, the focus of the work is to develop
QD-based sensors that operate through an electron transfer mechanism.
Chapter 3 discusses the synthesis and characterisation of CdSe and
CdSe/ZnS QDs. Three different sized QDs were prepared each with
distinct emission wavelengths. The sizes of these nanoparticles were
determined by three methods, transmission electron microscopy (TEM),
dynamic light scattering (DLS) and by a UV-vis method.
Surface functionalisation of these synthesised QDs (chapter 4) with
mercaptosuccinic acid rendered them water soluble and were shown to
display selectivity for Cu2+ over a number of biologically relevant metal
ions. The negatively charged surface of the QDs and the position of copper
in the Irving-William series were believed to be responsible for this
interaction. Positively charged CdSe/ZnS QDs were also prepared and
were shown to detect ATP and to a much lesser extent GTP over the other
nucleotides screened. The greater net negative charge of the ATP and GTP
when compared to their mono and diphosphate analogues was the likely
cause of this discrimination.
In chapter 5 the relatively unexplored field of anion sensing with
QDs was examined using charge neutral urea and thiourea receptors.
Based on a design by Gunnlaugsson et al, a CdSe/ZnS QD with a thiourea
receptor anchored to its surface displayed similar PET-mediated fluorescence quenching as an organic dye sensor containing the same
receptor. A ferrocenyl urea receptor was also anchored to a QD surface
and shown to “switch off” the QD’s fluorescence emission. On addition of
fluoride ions the emission was restored, most likely due to a modulation of
the ferrocene’s redox activity.
In chapter 6 the assembly of Schiff base receptors on the surface of
preformed CdSe/ZnS QDs were shown to arrange in such a way to enable
the simultaneous detection of Cu2+ and Fe3+. The intriguing aspect of this
study was that the receptors themselves displayed no selectivity for any
metal ion until they were assembled on the QDs. Recognition was also
confirmed by a distinct colour change visible to the naked eye.|
|Appears in Collections:||Theses (Pharmacy & Life Sciences)|
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