Browsing by Author "Mushonga, Paul"

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    Fabrication of type-I indium-based near-infrared emitting quantum dots for biological imaging applications
    (University of the Western Cape, 2013) Mushonga, Paul; Onani, Martin; Madiehe, Abraham
    Semiconductor nanocrystals or quantum dots (QDs) are fluorescent nanometer-sized particles which have physical dimensions that are smaller than the excitonic Bohr radius, large surface area-to-volume ratios, broad absorption spectra and very large molar extinction coefficients. Biomedical applications of QDs are mainly based on II-VI QDs containing cadmium, such as CdSe/ZnS. These cadmium-based systems are associated with high toxicity due to cadmium. As a result, potential replacements of cadmium-based QDs in biological applications are needed. In this study, InP/ZnSe QDs were synthesized for the first time using a one-pot hot injection method. Furthermore, a growth-doping method was used for silver, cobalt and iron incorporation into the InP core. Water compatibility was achieved through ligand exchange with 3- mercaptopropionic acid. In vitro cytotoxicity and imaging/internalization of the as-prepared MP A-InP/ZnSe and MP A-capped CdTe/ZnS QDs were evaluated. InP/ZnSe QDs were successfully synthesized with ZnSe shell causing a 1.4 times reduction in trap-related emission.
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    One-pot synthesis and characterization of InP/ZnSe semiconductor nanocrystals
    (Elsevier, 2013) Mushonga, Paul; Onani, Martin O.; Madiehe, Abram M.; Meyer, Mervin
    We report on the one-pot synthesis of InP/ZnSe quantum dots (QDs) using a precursor-based colloidal synthesis in a noncoordinating solvent environment. The structural and optical studies were carried out on the as-prepared InPQDs. The quantum yield of the nanocrystals was recorded as 6% and a 1.4 times reduction in the ratio of trap-related emission to band edge emission was observed on ZnSe passivation of the InPQDs.
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    Synthesis and characterization of zinc-doped magnetic nanoparticles for diagnostic studies
    (University of the Western Cape, 2015) Allard, Garvin Richard Johan; Onani, Martin; Mushonga, Paul; Meyer, M.
    In the present study we report the synthesis and characterization of iron oxide magnetic nanoparticles doped with zinc in an attempt to enhance the magnetic properties. The nanoparticles were prepared via the co-precipitation route and capped with 3-phosphonopropionic acid (3-PPA). The amount of zinc dopant was varied to yield nanoparticles with the general formula ZnxFe3-xO4 (x=0, 0.1, 0.2, 0.3, 0.4). Characterization was carried out using high resolution transmission electron microscopy (HRTEM), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and superconducting quantum interference device (SQUID) analysis. Results from HRTEM, XRD and SQUID confirm that doping took place and x=0.2 was found to be the doping limit for these nanoparticles with a maximum size of 10.73 nm and saturation magnetization of 73.37 emu/g. The EDS further confirmed successful doping with zinc, while FTIR and TGA confirmed successful capping with 3-PPA. Despite agglomeration at all doping levels, these nanoparticles show great potential for application in breast cancer diagnostic studies.