Synthesis And Luminescence Of Mixed-Halide And Mixed-Metal Nanocrystals

SYNTHESIS AND LUMINESCENCE OF MIXED-HALIDE AND MIXED-METAL NANOCRYSTALS by DULANI MENIKE DHANAPALA BAJJALA KUMBURE GEDARA MAY 2022Advisor: Prof. Federico A. Rabuffetti Major: Chemistry (Inorganic) Degree: Doctor of Philosophy Rare-earth-doped upconverting phosphors show unique luminescence features such as large anti-Stokes shifts and narrow emission bands. Further, their luminescent emission is not affected neither by photoblinking nor by photobleaching. Also, it is possible to achieve excitation and emission within the optical transparency window of biological tissues (600–1300 nm), which provides deep tissue penetration depth. This feature makes rare-earth-doped upconverting nanocrystals (UCNCs) suitable for biomedical applications such as biosensing and bioimaging. Despite the intrinsic advantages of UCNCs in biophotonic applications such as imaging and sensing, realization of their full potential as optical probes has been hindered by the inability to design upconverting nanomaterials with targeted luminescence response, both in terms of chromaticity and temperature sensitivity. With the aim of bridging this knowledge gap, this Dissertation focuses on: (1) identifying host materials that enable understanding the effect of host’s composition and crystal structure on luminescence response. This requires a family of materials in which compositional changes systematically tune structural features directly involved in luminescence. (2) developing colloidal synthetic routes to obtain high-quality nanocrystals. (3) systematically investigate the nanocrystals’ luminescence response as a function of host composition, doping level, and temperature. To accomplish these goals, we selected alkaline-earth fluorohalides of formula MFX (M = Ca, Sr, Ba; X = Cl, Br, I) and alkali–manganese fluorides of formula AMnF3 (A = Na, K, Rb, Cs) as host materials