Composite materials based on quantum dots and polymer matrices for gamma radiation registration in the next-generation scintillation detectors

BACKGROUND: The development of new scintillation materials based on fluorescent nanocrystals with a perovskite structure of CsPbBr3 composition and CdSe/ZnS quantum dots is a pressing topic that is being pursued by numerous scientific groups [1–4]. Both of these materials have a high potential for application in this role due to their excellent fluorophore properties, with a quantum yield of luminescence of approximately 100%. Additionally, they possess high values of the effective atomic Zeff number. The photoelectric cross section is dependent on Zeff as (Zeff)5, while the magnitude of X-ray absorption is dependent on Zeff as (Zeff)4/(AE3), where A is the atomic mass of the substance absorbing the γ-quantum and E is the energy of the X-ray photon [5].

AIM: The aim of the study was to develop a technique for fabricating scintillators based on quantum dots and polymer matrices with a high degree of transparency, high temporal stability of luminescence quantum yield, and short luminescence decay times (time of illumination or average lifetime of the substance in the excited state) for gamma-ray registration.

MATERIALS AND METHODS: A HAMAMAMATSU R7400U-6 photomultiplier tube was employed to register scintillation signals. A 137Cs source with a γ-quantum energy of 661.7 keV was used as a source of ionizing radiation.

RESULTS: At irradiation with γ-quanta of 137Cs isotope samples based on poly(para-methylstyrene) matrix cross-linked with divinylbenzene molecules (10% wt%), activated with naphthalene (10%, primary acceptor), anthracene (1%) and quantum dots/perovskite nanocrystals (0, 1–1.0%, re-emitter), the energy spectrum showed effective Compton scattering of gamma-quanta in matter on atoms included in quantum dots/perovskite nanocrystals.

The study revealed that samples devoid of inorganic elements, including quantum dots and perovskite nanocrystals, do not exhibit the Compton effect for gamma-quanta. Furthermore, the paramethylstyrene matrix serves to safeguard perovskite nanocrystals from external influences. The photoluminescence quantum yield of bulk composite materials based on perovskite nanocrystals of the CsPbBr3 composition and poly(paramethylstyrene) remains constant over an extended period, with minimal fluctuations within the margin of error.

CONCLUSIONS: Experimental evidence has demonstrated that quantum dots and perovskite nanocrystals encapsulated in various polymer matrices exhibit scintillator properties when subjected to ionizing radiation. The fabricated samples of perovskite nanocrystals/quantum dots and various polymers have been identified as the most promising candidates for use as scintillation material for the registration of X-ray and gamma radiation.