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Title: Enhanced upconversion photoluminescence by novel plasmonic structures
Author: Qin, Heng
ISNI:       0000 0004 8504 6285
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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The emerging field of plasmon-enhanced upconversion photoluminescence has a significant impact on a variety of technologies, including high-efficiency solar energy systems and biotechnology. To date, the upconversion efficiency of best reported rare-earth doped upconversion nanoparticles cannot meet the requirements of practical utilizations in these fields. Therefore, it is of great significance to find new approaches for the enhancement of upconversion efficiency. This thesis mainly aims to explore the enhanced upconversion photoluminescence by several novel plasmonic nanostructures. In this PhD work, I first studied the properties of rare-earth doped upconversion nanomaterials, which are capable of the spectral conversion of the otherwise lost sub-band-gap photons from the solar spectrum. The extra Gd3+ ion doping strategy was introduced in the hydrothermal synthesis process, which can provide an approach to tune the geometry and upconversion efficiency of upconversion nanoparticles (UCNPs). To achieve higher upconversion efficiency, advances in the experimental improvements in plasmon-enhanced upconversion photoluminescence (UCPL) efficiency are explored, by using Au mesoporous film, Au nanotriangle array or nanohole array substrates for the enhancement of upconversion photoluminescence. It is demonstrated that the best plasmonic nanostructures can achieve about 360 times UCPL enhancement. These experimental results demonstrated the great potential of the plasmonic effect for UCPL enhancement. Furthermore, a triplet-triplet annihilation based upconversion nanoparticles (TTA-UCNPs) were synthesized, which have much higher intrinsic upconversion efficiency than the rare-earth based upconversion nanoparticles. A plasmon-enhanced upconversion photoluminescence substrate was designed for high performance photocatalysis applications under solar simulator (AM 1.5 G) irradiation. Five times faster photocatalytic activity rate was achieved by this plasmonic/TTA-UCNPs/Au@TiO2 system, which demonstrates great value of plasmonic and upconversion mechanisms. The combination of excellent plasmonic substrate and high efficiency TTA-UCNPs makes it possible for the realization of industrial level applications of the plasmonic and upconversion in the photocatalytic field.
Supervisor: Xie, Fang ; Ryan, Mary Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral