Hu Yichen,Ma Jiaju,Liu Tonghuan,Zhang Yongjie,Yu Yuhong,Sun Zhiyu,Fang Fang,Dong Tianhao,Zhao Yanhong,Zhou Gen
In this paper, three polymeric bases (styrene, vinyl toluene, methyl methacrylate (MMA)) plastic scintillators were synthesized by thermal and UV irradiation polymerization. The influences of the concentrations of the primary fluorescent agent 2.5-diphenyloxazole (PPO) and wave-shift agent 1,4-bis-2(5-phenyloxazoyl)benzene (POPOP) on plastic scintillators characterization were investigated. The results suggest that the maximum emission wavelength of synthesized plastic scintillators with different polymeric base are all around 423 nm matching with maximum response wavelength of general photoelectric devices, and its decay time with several nanoseconds has reached the same level as the EJ-200. The maximum light yield of the plastic scintillator was achieved when the mass ratio of PPO/POPOP is 1.0%/0.02% for the styrene plastic scintillators.
This study introduces a facile method for the controlled growth of addressable planar arrays of highly luminescent, catalyst-free 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) nanowires. By employing a hollow mask over a faceted sapphire substrate, simultaneous control over the position and orientation of the nanowires is achieved through a mask-confined graphoepitaxial growth, offering substantial advantages over traditional post-growth assembly techniques. High-temperature annealing creates parallel nanogrooves on the sapphire surface, inducing a graphoepitaxial effect that aligns the nanowires with a consistent [102] crystallographic axis. The hollow mask further aids in precisely localizing nanowire growth through its shadowing effect. Optoelectronic investigations reveal that these nanowires emit intense and stable blue photoluminescence at room temperature, with a broad spectrum spanning from 400 to 600 nm. This luminescence is achieved through excitation by continuous-wave ultraviolet light or two-photon absorption using femtosecond infrared light. Notably, the emission quantum efficiency of POPOP nanowires reaches 59 %, a remarkable improvement over the 12 % observed in powder counterparts when excited with 405 nm light. Transit absorption spectra indicate that ground state bleaching and excited state absorption display consistent kinetics within a 100 ps time window, suggesting the same origin from singlet excitons. The precise alignment and positioning of these nanowires make them viable for in-situ integration into photodetectors with rapid ultraviolet light responses. This study advances the controlled growth of catalyst-free nanowire arrays and enhances the understanding of the optoelectronic properties of POPOP nanowires.
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