Allison Lim


Materials Chemist

Bismuth Dopants for Gamma Ray Spectroscopy in Plastic Scintillators


Problem:
Plastic scintillators can detect neutrons or gamma rays and even distinguish the two via PSD. However, they are not able to determine source, or radioactive isotope, that emitted the radiation. Gamma ray spectroscopy would allow plastic scintillators to identify the source of radiation - for example, whether the gamma ray came from potassium (bananas) or uranium (nuclear materials...).

Hypothesis:
Incorporating high Z elements into plastic scintillators will lead to the photoelectric effect, allowing plastic scintillators to be used for gamma ray spectroscopy. Bismuth dopants are a good candidate due to bismuth's low toxicity, compared to tin and lead, and wide range of organobismuth molecules available.

Summary of Results:
  • Three types of bismuth dopants, triarylbismuth, trialkoxybismuth, and bismuth oxide dopants were synthesized.
  • Triarylbismuth dopants were soluble but not stable under polymerization conditions.
  • Trialkoxybismuth dopants were stable under polymerization conditions but insoluble in vinyl toluene.
  • Bismuth oxide nanoparticles did not disperse in vinyl toluene, but could be functionalized to improve dispersion.
Bismuth dopants synthesized for gamma ray spectroscopy in plastic scintillators.