- Title
- A Facile Effective Method for the Synthesis of Au-Cdse Nanostructures and their Characterisations.
- Creator
- Gaxela, Nelisa Ncumisa
- Date Issued
- 2016-5
- Date
- 2016-5
- Type
- Masters theses
- Type
- text
- Identifier
- http://hdl.handle.net/11260/3238
- Identifier
- vital:43198
- Description
- ABSTRACT We report the synthesis of aqueous and organically soluble cadmium selenide (CdSe) nanoparticles (NPs) doped with gold via a facile and effective method. Briefly the synthesis involves the reduction of selenium powder using sodium sulphite to produce sodium selenosulphate which acts as the selenium source, followed by the addition of CdX (X = Cl2, CH3COO, NO3). The nanoparticles were passivated with trisodium citrate, mercaptopropanoic acid (MPA), potassium sodium tartarate (PST) and L-cysteine which rendered them soluble in water and also acted as stabilizing agents, while passivation with hexadecylamine (HDA) made them soluble in organic solvent which also enhanced their stability. The high quality of the as-synthesized nanoparticles was confirmed using absorption and photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The systematic study of the effect of mole ratio, temperature, capping agent, growth time, cadmium precursor and ratio of Au on the size, optical and structural properties on the water soluble CdSe nanoparticles were investigated. All the as-synthesised particles, are blue-shifted in relation to the bulk band gap of CdSe. As the Cd: Se mole ratio increases, the intensity of the citrate capped CdSe materials also increases and the particle sizes are in the range of 2.06 – 4.00 nm. When the temperature was increased, the luminescence intensity quenched whereas the particle size increased. As the growth time increased, the intensity increased and then decreased again towards the end of the reaction. When different capping agents were used the particle sizes range from 2.06 – 3.36 nm for citrate, 2.08 – 3.33 nm for MPA, 2.01 – 2.28 nm for L-cysteine and polydispersed for PST. The luminescence intensity decreased in the order citrate > cysteine > PST > MPA when CdCl2 was used as cadmium precursor. When different cadmium precursors were used for L-cysteine, the particle sizes range from 2.06 – 2.31 nm for Cd(CH3COO)2 and 2.00 – 2.37 nm for Cd(NO3)2 while the intensity increased as the reaction time increased, however, still lower than the CdCl2 materials. The effect of Au ratio showed that the intensity of Au-doped cysteine capped-CdSe increased as the Au ratio decreased. The systematic study of the effect of temperature and growth time in the organic soluble CdSe nanoparticles on the size, optical and structural properties was also investigated. All the as-synthesised particles were blue-shifted in relation to the bulk CdSe. As the temperature increased the particle sizes of the undoped materials range between 2.92 – 2.95 nm at 160 °C and 5.35 – 5.39 nm at 200 °C while for the doped materials the particle size range from 2.53 – 2.61 nm at 160 °C, 3.97 nm at 200 °C and 4.20 – 4.72 nm at 240 °C. The intensity of the doped materials increased as the reaction time increased and then decreased again towards the end of the reaction. After ligand exchange the intensity of the as-synthesized doped and undoped-CdSe NPs was very low compare to the parent organically capped doped and un-doped CdSe. It was discovered that without any further purification, the quality of the materials formed by this method is comparable to that of the best CdSe NPs reported in the literature. This method is safe, inexpensive and reproducible.
- Description
- Thesis (MsC Chemistry) -- Faculty of Natural Sciences, 2019
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (61 pages)
- Format
- Publisher
- Walter Sisulu University
- Publisher
- Faculty of Natural Sciences
- Language
- English
- Rights
- Walter Sisulu University
- Rights
- All Rights Reserved
- Rights
- Open Access
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | A Facile Effective Method for the Synthesis of Au-Cdse Nanostructures and their Characterisations _done.pdf | 4 MB | Adobe Acrobat PDF | View Details Download |