Imaging techniques have been developed for decades for the detection of biomolecules in
biomedicine cells, in vitro or in living cells and organisms. The application however, often
constrained by the available probes, whose optical properties may limit the imaging possibilities.
It is very essential to improve the sensitivity of these devices by enhancing efficiency to detection.
Recently, Fe3O4 has been used primarily in cancer theranostic application such as magnetic
resonance imaging (MRI). However, its toxicity towards normal cells has been pointed out by
scientific communities, when they are involved in in vitro (helics) cancer treatment. In this work,
we have chosen to use α-Fe2O3, because it has proven to be less toxic than Fe3O4. Hematite is
antiferromagnetic (AFM) at room temperature with a small canted moment lying within the crystal
symmetry plane. At low temperature, hematite undergoes a magnetic phase transition from weak
ferromagnetic (WFM) to a pure antiferromagnetic configuration (AF), which is known as the
Morin transition. This magnetic property makes it possible for hematite to be applied in imaging
technique. To enhance the optical properties, the α-Fe2O3 is doped with lanthanide ions due to their
unique optical properties. Incorporation of these rare earth ions, enable the α-Fe2O3 to have
enhance luminescence properties.
Imaging techniques have been developed for decades for the detection of biomolecules in
biomedicine cells, in vitro or in living cells and organisms. The application however, often
constrained by the available probes, whose optical properties may limit the imaging possibilities.
It is very essential to improve the sensitivity of these devices by enhancing efficiency to detection.
Recently, Fe3O4 has been used primarily in cancer theranostic application such as magnetic
resonance imaging (MRI). However, its toxicity towards normal cells has been pointed out by
scientific communities, when they are involved in in vitro (helics) cancer treatment. In this work,
we have chosen to use α-Fe2O3, because it has proven to be less toxic than Fe3O4. Hematite is
antiferromagnetic (AFM) at room temperature with a small canted moment lying within the crystal
symmetry plane. At low temperature, hematite undergoes a magnetic phase transition from weak
ferromagnetic (WFM) to a pure antiferromagnetic configuration (AF), which is known as the
Morin transition. This magnetic property makes it possible for hematite to be applied in imaging
technique. To enhance the optical properties, the α-Fe2O3 is doped with lanthanide ions due to their
unique optical properties. Incorporation of these rare earth ions, enable the α-Fe2O3 to have
enhance luminescence properties.
These lanthanide-doped nanoparticles (UCNPs) undergoes up-conversion process which have
remarkable ability to combine two or more low energy photons to generate a singly high energy
photon by an anti-stokes process and hold great promise for bio-imaging. These nanoparticles
exhibit excellent photostability, continuous emission capability and sharp multi-peak line
emission. With near infrared excitation, light scattering by biological tissues is substantially
reduced. α-Fe2O3 have been singly and co-doped with Holmium, Thulium, and Ytterbium by both
sol-gel and microwave methods. The doping of these lanthanides have shown improved
luminescent properties of α-Fe2O3. The up-conversion has been observed from co-doping Thulium
and Ytterbium. This work is a proof of concept to show the up-conversion in α-Fe2O3. However,
the up-conversion intensity is low about 200000 CPS maximum observed, this could be due to the
nature of the host structure quenching the luminescence. There is rather, a need to increase the
intensity for the maximum application to be achieved. / Physics
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/26881 |
| Date | 04 1900 |
| Creators | Mathevula, Langutani Eulenda |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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