UC Irvine

Organic plastic scintillators are employed as radiation detectors in industries and are used for nuclear safeguard applications. They are durable, can be produced at low cost and can readily be used in portable devices, making them ideal for field detection work. Their fast decay time also allow them to discriminate different types of radiation making them useful in various applications. Still, their drawbacks include low Z value resulting in limitations on the energy resolution and the ability of identification of radioactive sources. To resolve this issue dopants such as dyes and nanoparticles are added into the polymer matrix in an attempt to enhance either light yield and/or the overall Z. Nanophosphors such as quantum dots is a popular choice due to their tunable emission and energy transfer properties. However, over the past decade the coupling of these nanocrystals, having emission in the visible wavelength, with plastic scintillators were not very successful.

In the current dissertation, a different approach is implemented using nanophosphors in the UV region. Cadmium Sulfide quantum dots with near UV emission is embedded into plastic scintillating system under minute loading. Scintillation efficiency was enhanced at different weight loading of dyes and quantum dot, characterization was also performed at various ionizing energies demonstrating improvements. The study was further expanded with different dyes and polymer combination displaying various degree of enhancement and quenching through energy transfer effects. Lastly, deep UV emission ZnO nanocrystals were synthesized to further study the energy transfer effects of the dye and polymer combination. The fabrication process and results are discussed in the following.