Abstract
The popularity of quantum dots (QDs) in the field of fluorescence has given rise to new methods for generating a diverse selection of nanoscale electromagnetic radiation sources. These emissions range from ultraviolet, crossing the visible light spectrum towards IR and NIR.In this project, various near-infrared mercury chalcogenide (HgTe and HgSe) nanocrystals have been synthesised and analysed, describing new experimental strategies for the formation of these QDs. The newly developed methods seek to improve the fluorescent efficiency and characteristics of the QDs as well as reducing toxicity and increasing their stability. The absorption and emission spectra combined with the transmission electron microscope (TEM) images and X-ray diffraction (XRD) data determine the structure of the nanoparticles and allow understanding of their nature. By using an integrating sphere technique, quantum yields (QY) can be measured as a means to determine the fluorescent efficiency of these QDs and devise methods of improving this feature. These areas of analysis are the fundamental factors that define the characteristics of these QDs.
Luminescent mercury selenide (HgSe) quantum dots have been synthesised at room temperature by a phosphine-free method using oleic acid as a capping agent. The modification of experimental conditions such as temperature resulted in particles of various sizes (15–100 nm) and morphologies not previously seen in HgSe, with emission tunable between 1000 nm and 1350 nm.
A similar technique was used to synthesis mercury telluride (HgTe) quantum dots without the use of trioctylphosphine or trioctylphosphine oxide as a means to encourage a phosphine-free methodology. Using liquid nitrogen, the sudden temperature reduction during synthesis resulted in highly monodispersed nanoparticles with NIR absorption and emission properties.
Finally, mercury telluride HgTe nanoparticles were biosynthesised in Allium Fistulosum (common spring onion) through a mutual antagonistic reaction. Exposure of common Allium Fistulosum to mercury and tellurium salts under ambient conditions resulted in the expulsion of crystalline, non-passivated HgTe quantum dots that exhibited emissive characteristics in the near-infrared spectral region, a wavelength range that is important in telecommunications and solar energy conversion.
| Date of Award | 1 Jul 2020 |
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| Original language | English |
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| Supervisor | Mark Green (Supervisor) & Anatoly Zayats (Supervisor) |