Zinc oxide/polystyrene composite based scintillator for alpha particle monitoring

Abstract

The preparation of Zinc oxide/polystyrene (ZnO/PS) composite scintillator was carried out with different percentages of ZnO varying from 5 to 50% (w/w) on the quartz substrate. The enhanced absorbance is observed at ~ 385 nm for low % (w/w) of ZnO, which is red-shifted to 390 nm for higher ZnO % (w/w) composite samples. The pristine polystyrene sample showed excitation at ~271 nm, equivalent to the measured bandgap of polystyrene. A photoluminescence emission of 385 nm in ZnO/PS composite is observed, which is equivalent to the measured ZnO bandgap ~3.22 eV. Alpha excited radioluminescence, obtained using 5.2 MeV alpha particles from 239Pu, showed emission at ~387 nm together with polystyrene emission at ~ 430 nm. The scintillation characteristics for the composite samples are investigated using the pulse height spectrum after coupling the composite films with a photomultiplier tube (PMT) and multichannel analyzer (MCA). The significant increase in pulse height is observed for 5% (w/w) or more ZnO in PS. This is clearly discernible in contrast to polystyrene without ZnO. The integrated counts increase linearly up to 20% (w/w) ZnO and showed reduction for 50% (w/w) ZnO/PS sample. The reduction in the counts is attributed to the reduced transmittance for higher % (w/w) ZnO in PS matrix. The maximum detection efficiency and minimum detectable activity (MDA) are ~23% and ~0.4 Bq, respectively, for 50% (w/w) ZnO/PS. Further, a linear response is observed with activity for all scintillating samples. These findings suggest that ZnO/PS composite materials may be a good candidate for efficient monitoring of alpha radioactivity with high sensitivity and very low MDA.