Development of novel plastic scintillators based on polyvinyltoluene for the hybrid j-pet/mr tomograph

Figure 12 Absorption (green solid line) and emission (red dashed line) spectra of POPOP in cyclohexane [69]. 
 
In the case of 2-(4-styrylphenyl)benzoxazole, the Stokes shift resulting from the 
difference between peaks of 402 nm and 349 nm, is equal to 53 nm. This value is 
comparable 
to 
Stokes 
shift 
of 
POPOP. 
Therefore 
Stokes 
shift 
of
2-(4-styrylphenyl)benzoxazole is sufficient to use the substance as a scintillator dopant. 
Another issue which is necessary to consider is adjustment of the primary additive 
to the 2-(4-styrylphenyl)benzoxazole to provide an effective energy transfer. According to
Fig. 5, in plastic scintillator the energy is transferred from primary to secondary fluor in the 
way of fluorescence. However to provide an effective transfer of energy, emission 
spectrum of primary fluor has to overlap with absorption spectrum of secondary fluor. In 
Fig. 13 and Fig. 14 absorption and emission spectra of plastic scintillating additives are 
presented. As a primary additive 2,5-diphenyloxazole (PPO) and p-terphenyl (PTP) were 
considered while 2-(4-styrylphenyl)benzoxazole (novel WLS) is assumed to act as
a wavelength shifter, which is secondary additive. 
In both sets of mixture: PPO + novel WLS and PTP + novel WLS, the emission 
spectrum of the primary fluor overlaps with the absorption spectrum of secondary fluor. In 
case of PPO, their maxima fits almost perfectly to each other, while PTP and novel WLS 
maxima are slightly shifted within few nanometers. 

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Wavelength [nm]
PPO absorption
PPO emission
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novel WLS emission