Bismuth-Loaded Polymer Scintillators for Gamma Ray Spectroscopy

Abstract

We synthesize a series of polyvinylcarbazole monoliths containing varying loadings of triphenyl bismuth as a high-Z dopant and varying fluors, either organic or organometallic, in order to study their use as scintillators capable of gamma ray spectroscopy. A trend of increasing bismuth loading resulting in a better-resolved photopeak is observed. For PVK parts with no fluor or a standard organic fluor, diphenylanthracene, increasing bismuth loading results in decreasing light yield while with samples 1 or 3 % by weight of the spin-orbit coupling organometallic fluor FIrpic, which emits light from both singlet and triple excitons, show increasing light yield with increasing bismuth loading. Our best performing PVK/ BiPh 3 /FIrpic scintillator with 40 wt % BiPh 3 and 3 wt % FIrpic has an emission maximum of 500 nm, a light yield of ~30,000 photons/MeV, and energy resolution better than 7% FWHM at 662 keV. Replacing the Ir complex with an equal weight of diphenylanthracene produces a sample with a light yield of ~6,000 photons/MeV, with an emission maximum at 420 nm and energy resolution of 9% at 662 keV. Transmission electron microscopy studies show that the BiPh 3 forms small clusters of approximately 5 nm diameter.

Luminescent Tris(8-hydroxyquinolates) of Bismuth(III)

“…The main focus concerning the development of new materials and improving efficiency of scintillators is to increase the radiation tolerance and maintain a high light output and transparency over several years. 15 A plastic scintillator generally contains a plastic base, a fluor, and a high-Z component. The base usually contains an aromatic group attached to a polymer backbone, such as polystyrene, while the attached dissolved fluor is an organic or inorganic emitter.…”

“…Radiation sensing is crucial for the detection of illicit nuclear weapons material, detection of toxic radionuclides potentially used in “dirty bombs”, and other national security applications. New materials that improve efficiencies of scintillators are needed to increase the radiation tolerance and maintain a high light output and transparency over several years . A desirable formulation for a plastic scintillator generally contains a plastic base, a fluor, and a high-Z component.…”

“…The base usually contains an aromatic group attached to a polymer backbone, such as polystyrene, while the dissolved fluor is an organic or inorganic emitter . Organic fluorophores trap singlet excitons but can have increased efficiency through triplet–triplet annihilation, − whereas heavy-metal emitters can trap both singlet and triplet excitons and increase the efficiency of plastic scintillators by as much as 3-fold. ,, A high-Z component metal is also desirable to enhance the cross-section for interaction with γ-rays in radiation sensors. ,, This study focuses on bismuth metal chelates that offer the potential for a high-Z emitting component in plastic scintillators. Bismuth is a low cost element and is the highest Z nonradioactive metal.…”

Influence of bismuth loading in polystyrene-based plastic scintillators for low energy gamma spectroscopy

“…Its main representative, Bi(Ph) 3 [1], was logically our prime choice for scintillation application following the existing literature. [26][27][28][29] But to understand the inuence of the Bi localization inside the matrix on the scintillation process it was also decided to synthesize the molecule [7], Bi(biPh) 3 . For that purpose a synthetic route based on an organo-lithium reagent was used (Scheme 2), providing good isolated yield, and purity was conrmed with the characteristic 13 C NMR signal of the C-Bi: 153.8 ppm.…”

“…For gamma detection the principal focus has been Sn, 12,13 Gd, [14][15][16][17][18] Pb [19][20][21][22][23][24][25] and Bi. [26][27][28][29] Bismuth has the highest Z among non-radioactive atoms, which makes it a target of choice. Furthermore its derivatives are less toxic than lead or tin equivalents.…”