Synthesis of Monodisperse Nanoscintillators at High Temperatures for Biomedical Relevant Applications

Luminescent sub-100 nm particulates continuously generate immense research interest in the biomedical field for imaging, theranostics, and optogenetics. Conventionally, upconversion nanoparticles or UV activated semiconductors are studied, however these materials are limited by biological barriers such as the skin which reduces the penetration depth of these excitation sources, tissue\u27s auto- fluorescence, and toxicity. One approach to overcome these challenges is to use nanoscintillators (sub-100 nm materials that can generate visible light using high energy excitation sources such as x-rays) which can generate light locally to the human body. Numerous scintillators have been reported since the discovery of x-rays from the famous Roentgen experiment. The brightest and most commonly used scintillator in the biomedical field is a single crystal lutetium oxyorthosilicate doped with cerium (Lu2SiO5:Ce, LSO:Ce) for its high optical output, short decay time, and minimal self-absorbency. Alternative nanoscintillators that have potential for biomedical applications are different derivatives of the silicate family such as lutetium pyrosilicate and yttrium pyrosilicate. These crystal can be synthesized using different high temperature melt-growth processes. Consequently, the affinity for nanoparticles to sinter makes this a difficult material\u27s challenge. This dissertation is presented in three parts on a technique that can synthesize non-aggregated and highly crystalline sub-100 nm refractory particulates that can scintillate. First the synthetic technique coined the high temperature multi-composite reactor is presented where monodisperse yttrium and lutetium pyrosilicate (Lu2Si2O7:Ce) nanoparticles were synthesized above 1000oC. Afterwards different energy transfer mechanisms were examined by using different lanthanide activators (Ce3+, Tb3+, and Eu3+) to target specific wavelength emissions and increase the overall optical output. Lastly, these nanoscintillators were surface modified with different organic moieties (organic dyes, bovine serum albumin, and polypropargyl acrylate) that can couple to different biological conjugates using a copper-catalyzed azide-alkyne cycloaddition reaction. The work presented here will emphasize the biomedical applications where the scintillators synthesized have the potential to couple to light sensitive protein known as opsins for optogenetics. The organic compounds that will be investigated are bovine serum albumin to increase the nanoparticles biocompatibility, indocyanine green dye as an infrared biotracer, and rose bengal for X-ray induce photodynamic therapy