Structural Variation of Carbazole Derivatives for Plastic Scintillation Applications

The preparation of various plastic scintillators with embedded carbazole moieties is reported. As a result of their versatility and advantageous luminescence properties, this system is a candidate of choice for such applications. Through careful system design, the carbazole in the system can have a variety of functions, for example as the polymer matrix, as the primary fluorophore or as the secondary fluorophore. For systems in which carbazole is embedded in the polymer matrix, poly(N-vinylcarbazole) (PVK) and poly(styrene-co-N-vinylcarbazole) were prepared by bulk radical polymerization. For application as a primary or secondary fluorophore, N-(2-ethylhexyl)carbazole (EHCz) is a particularly suitable molecule. When used at a low concentration it can act either as a primary fluorophore (when coupled with 1,4-bis(5-phenyloxazol-2-yl) (POPOP) or bis-(2-methylstyryl)benzene (bis-MSB) as the wavelength shifter), or as both primary and secondary fluorophore if the concentration inside the polymer matrix is high. The performance of EHCz was compared with the related molecule N-(ethyl)carbazole. Finally, another carbazole-containing molecule 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene was loaded in a polymer matrix as the secondary fluorophore. Scintillation results show its efficiency to shift the scintillation response to wavelengths close to 500nm. The preparation and primary photophysical properties of each of these new plastic scintillators was reported, in addition to the scintillation properties of each. These results highlight the potential application of carbazole derivatives as fluorophores for nuclear detection.