Abstract
Lanthanide (Ln3+)-doped upconverting nanoparticles (UCNPs) are paid innumerable attention due to wider applications in energy production/harvesting and biological field. Such UCNPs possess a number of advantages like tuneable emission in a wide range (ultraviolet, UV to near-infrared, NIR), high spatial emission resolution, deep tissue penetration depth of NIR excitation light and low autofluorescence background signal, for instance. However, NIR light with low photon energy cannot directly induce the photoactivation of most semiconductors (e.g. ZnO, BiVO4, and TiO2) in the process of solar energy conversion. Researchers are in search of promising materials that can absorb NIR photons and convert that energy into UV and visible ones that can then be used to photoexcite the said semiconductors. Following this concept, in this project, Ln3+-doped UCNPs together with semiconductors will be used to develop such nanocomposite photocatalyst that could show efficient photocatalytic activity under UV-Vis-NIR illumination (i.e. entire solar spectrum). Moreover, in case of bioimaging applications, the 980 nm laser, generally applied to trigger the Yb3+-sensitized upconversion processes is strongly absorbed by water molecules in biological structures and could cause severe overheating effects that damage cells and tissues. To address this problem, recent research has focused on the extension of upconversion excitation spectrum to shorter wavelengths (especially, in the vicinity of 808 nm), where water molecules do not absorb significantly. To address the issue of NIR laser induced tissue damage, this project will also be focused to introduce Nd3+ ions as NIR absorbers and sensitizers in the conventional Yb3+-doped core/shell or core/shell/shell UCNPs to ensure successive energy transfer in a mono or bi-directional manner. NIR dye-sensitized upconversion emission would also be tested as a strategy to shift the excitation to a shorter wavelength without compromising the excitation efficiency. Therefore, in this project tenure, Nd3+-sensitized core/shell and core/shell/shell UCNPs will be examined for their potential in bioimaging and photodynamic therapy (PDT) applications using the state-of-the-art research infrastructure. (AU)
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