Abstract
Exciton confinement within nanoparticle quantum dots results in electronic and optical properties not exhibited within bulk material semiconductors of the same composition. This thesis reports how loading CuInS/ZnS quantum dots in polyvinyl toluene (PVT)-based plastic scintillator increased peak emission intensity and wavelength. Five core/shell quantum dot materials were dispersed within toluene and characterised for suitability in loaded scintillators: CdSe/ZnS, ZnCdSe/ZnS, ZnCdSeS, ZnCuInS/ZnS, and CuInS/ZnS. The CuInS/ZnS quantum dots exhibited the brightest emission and a 180±1 nm Stokes shift large enough for negligible selfabsorption. Various masses of CuInS/ZnS quantum dots were loaded into EJ-290 plastic scintillator casting resin with three different loading regimes: homogeneous, sedimented layer, and a hybrid between the two. Loading within these casting scintillators was confirmed and characterised through energy-dispersive X-ray spectroscopy. Transmission spectra of the quantum dot loaded and unloaded cast scintillators were obtained and showed the presence of CuInS/ZnS increased the opacity, particularly for the highly concentrated layers in the sedimented and hybrid
loaded scintillators. Scintillator absorption was shifted by quantum dots, with dual-component absorption edges for homogeneous and thin or poorly covered sedimented layers and a dominant CuInS/ZnS absorption edge for thick sedimented layers and hybrid loaded scintillators. Comparisons between quantum dot loaded and unloaded
scintillator emission were assessed through laser and X-ray induced luminescence. Photoluminescence from unloaded plastic scintillator showed peaks at 425nm and 440 nm; inclusion of CuInS/ZnS quantum dots resulted in an additional luminescence peak at 550nm with increased intensity. The brightest photoluminescence was from homogeneous scintillators followed by sedimented and hybrid loaded, indicating that self-absorption in the highly concentrated sedimented layers limited output emission. X-ray luminescence of quantum dot doped plastic scintillator exhibited the same peak wavelength shift and increased intensity. The brightest emission was from the sedimented, next hybrid, and then homogeneous scintillators, attributed to the increased X-ray stopping power of highly concentrated CuInS/ZnS sedimented layers. The sedimented loaded scintillators were brighter than unloaded EJ-290, indicating an increased detection efficiency compared to standard plastic scintillators.