Photophysical properties of zinc carboxy phthalocyanine-quantum dot conjugates
- Authors: Sekhosana, Kutloano Edward
- Date: 2013 , 2013-03-27
- Subjects: Phthalocyanines , Quantum dots , Zinc , Photochemistry , Atomic force microscopy , Transmission electron microscopy , Raman spectroscopy , Infrared spectroscopy , X-ray photoelectron spectroscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4276 , http://hdl.handle.net/10962/d1001652 , Phthalocyanines , Quantum dots , Zinc , Photochemistry , Atomic force microscopy , Transmission electron microscopy , Raman spectroscopy , Infrared spectroscopy , X-ray photoelectron spectroscopy
- Description: This thesis presents work based on the interactions of water soluble caboxylated zinc phthalocyanines (Pcs) and coreshell quantum dots (QDs). The Pcs are ZnPc(COOH)₈ and ZnPc(COOH)₄ and coreshell QDs are CdTe@ZnS-GSH. GSH = L-glutathione. Characterization and photophysical studies of conjugates were carried out. The approach of coordinating Pcs to QDs was achieved using an organic cross linker, N-N’-dicyclohexylcarbodiimide (DCC) at pH 10 at room temperature. Employing atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, infrared and X-ray photoelectron spectroscopies, the formation of the conjugates was confirmed. Upon conjugation with Pc derivatives, the fluorescence quantum yield of CdTe@ZnS-GSH decreased due to energy transfer from the QDs to the Pc. The average fluorescence lifetime of the CdTe@ZnS-GSH QD also decreased upon conjugation. The föster resonance energy transfer (FRET) behaviour of CdTe@ZnS-GSH-ZnPc(COOH)₄ conjugates was compared to that of CdTe@ZnS-GSH-ZnPc(COOH)₈. Higher FRET efficiencies were observed for CdTe@ZnS-GSH-ZnPc(COOH)₄-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₄-linked compared to the corresponding CdTe@ZnS-GSH-ZnPc(COOH)₈-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₈-linked. Triplet quantum yield (ΦT) and lifetime (ΤT) of ZnPc(COOH)₈ were found to increase in the presence of coreshell QDs. Though the singlet quantum yield (ΦΔ) value of ZnPc(COOH)8 was lower than ΦT , there was a slight upsurge in the ΦT in the presence of QDs. , Microsoft� Word 2010 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: Sekhosana, Kutloano Edward
- Date: 2013 , 2013-03-27
- Subjects: Phthalocyanines , Quantum dots , Zinc , Photochemistry , Atomic force microscopy , Transmission electron microscopy , Raman spectroscopy , Infrared spectroscopy , X-ray photoelectron spectroscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4276 , http://hdl.handle.net/10962/d1001652 , Phthalocyanines , Quantum dots , Zinc , Photochemistry , Atomic force microscopy , Transmission electron microscopy , Raman spectroscopy , Infrared spectroscopy , X-ray photoelectron spectroscopy
- Description: This thesis presents work based on the interactions of water soluble caboxylated zinc phthalocyanines (Pcs) and coreshell quantum dots (QDs). The Pcs are ZnPc(COOH)₈ and ZnPc(COOH)₄ and coreshell QDs are CdTe@ZnS-GSH. GSH = L-glutathione. Characterization and photophysical studies of conjugates were carried out. The approach of coordinating Pcs to QDs was achieved using an organic cross linker, N-N’-dicyclohexylcarbodiimide (DCC) at pH 10 at room temperature. Employing atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, infrared and X-ray photoelectron spectroscopies, the formation of the conjugates was confirmed. Upon conjugation with Pc derivatives, the fluorescence quantum yield of CdTe@ZnS-GSH decreased due to energy transfer from the QDs to the Pc. The average fluorescence lifetime of the CdTe@ZnS-GSH QD also decreased upon conjugation. The föster resonance energy transfer (FRET) behaviour of CdTe@ZnS-GSH-ZnPc(COOH)₄ conjugates was compared to that of CdTe@ZnS-GSH-ZnPc(COOH)₈. Higher FRET efficiencies were observed for CdTe@ZnS-GSH-ZnPc(COOH)₄-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₄-linked compared to the corresponding CdTe@ZnS-GSH-ZnPc(COOH)₈-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₈-linked. Triplet quantum yield (ΦT) and lifetime (ΤT) of ZnPc(COOH)₈ were found to increase in the presence of coreshell QDs. Though the singlet quantum yield (ΦΔ) value of ZnPc(COOH)8 was lower than ΦT , there was a slight upsurge in the ΦT in the presence of QDs. , Microsoft� Word 2010 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
Synthesis, optical and morphological characterization of CdSe/ZnSe quantum dots for cytotoxicity studies
- Authors: Nkaule, Anati Nomxolisi
- Date: 2013
- Subjects: Quantum dots , Quantum dots -- Optical properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10434 , http://hdl.handle.net/10948/d1020637
- Description: Colon cancer (CC) ranks high in morbidity and mortality amongst the most frequent occurring cancers worldwide. Mortality rates are mostly caused by mis-diagnosis and the poor efficacy of treatment. The aim of this study was to enhance our insights of quantum dots, for early detection and targeted drug delivery, thereby reducing toxicity to normal cells and reducing side effects that are caused by previous colon cancer medicine. The synthesis, characterization and cytotoxicity studies of CdSe/ZnSe quantum dots (QDs), nanocrystals are reported. Toxicological properties of the Cd2+ core are reduced by capping quantum dots with ZnSe, varying chain length and functional group ligands. Fluorescence wavelength and their size is improved by varying Cd2+ source and varying nanocrystal synthesis growth temperature. CdSe/ZnSe quantum dots are characterized with FT-IR to elucidate their structure. High-resolution transmission electron microscopy (HRTEM), X-Ray Diffraction (EDX), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) are used to measure their size and composition. Ligand exchange reactions are conducted with the use of 3-Mercaptopropanoic acid (3-MPA) to facilitate bio-compatibility and stability of CdSe/ZnSe QDs. Temperature stability of various ligand capped and stabilized CdSe/ZnSe QDs are measured by using thermogravimetric analysis (TGA). Caco-2 cell line is cultured from colon cancer, and cytotoxic studies are conducted to test for cell viability of various capped 3-Mercaptopropanoic acid (3-MPA) CdSe/ZnSe quantum dots at various concentrations. Myristic acid capped CdSe/ZnSe quantum dots produce high fluorescing mono-disperse quantum dots. The capping material, synthesis temperature and Cd2+ source of CdSe/ZnSe QDs affect fluorescence wavelength and thermal stability of quantum dots. Fluorescence wavelength is improved by using CdCl2.7H2O source of Cd2+. Cytotoxicity was found to be dependent on the concentration and the capping material of quantum dots. CdSe/ZnSe quantum dots toxicity is adjusted and reduced by varying the length, size and type of the capping ligand on the surface of quantum dots.
- Full Text:
- Date Issued: 2013
- Authors: Nkaule, Anati Nomxolisi
- Date: 2013
- Subjects: Quantum dots , Quantum dots -- Optical properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10434 , http://hdl.handle.net/10948/d1020637
- Description: Colon cancer (CC) ranks high in morbidity and mortality amongst the most frequent occurring cancers worldwide. Mortality rates are mostly caused by mis-diagnosis and the poor efficacy of treatment. The aim of this study was to enhance our insights of quantum dots, for early detection and targeted drug delivery, thereby reducing toxicity to normal cells and reducing side effects that are caused by previous colon cancer medicine. The synthesis, characterization and cytotoxicity studies of CdSe/ZnSe quantum dots (QDs), nanocrystals are reported. Toxicological properties of the Cd2+ core are reduced by capping quantum dots with ZnSe, varying chain length and functional group ligands. Fluorescence wavelength and their size is improved by varying Cd2+ source and varying nanocrystal synthesis growth temperature. CdSe/ZnSe quantum dots are characterized with FT-IR to elucidate their structure. High-resolution transmission electron microscopy (HRTEM), X-Ray Diffraction (EDX), Photoluminescence spectroscopy (PL) and Ultraviolet-visible spectroscopy (UV-Vis) are used to measure their size and composition. Ligand exchange reactions are conducted with the use of 3-Mercaptopropanoic acid (3-MPA) to facilitate bio-compatibility and stability of CdSe/ZnSe QDs. Temperature stability of various ligand capped and stabilized CdSe/ZnSe QDs are measured by using thermogravimetric analysis (TGA). Caco-2 cell line is cultured from colon cancer, and cytotoxic studies are conducted to test for cell viability of various capped 3-Mercaptopropanoic acid (3-MPA) CdSe/ZnSe quantum dots at various concentrations. Myristic acid capped CdSe/ZnSe quantum dots produce high fluorescing mono-disperse quantum dots. The capping material, synthesis temperature and Cd2+ source of CdSe/ZnSe QDs affect fluorescence wavelength and thermal stability of quantum dots. Fluorescence wavelength is improved by using CdCl2.7H2O source of Cd2+. Cytotoxicity was found to be dependent on the concentration and the capping material of quantum dots. CdSe/ZnSe quantum dots toxicity is adjusted and reduced by varying the length, size and type of the capping ligand on the surface of quantum dots.
- Full Text:
- Date Issued: 2013
- «
- ‹
- 1
- ›
- »