Fluorene Derivatives for Efficient Prompt Scintillation in Plastic Scintillators

Abstract

Plastic scintillators have been investigated for γ-ray detection with the promise of fast response, ease of scale up, and mechanical toughness. However, their low light yield has been a major limiting factor in the performance metrics. Herein, we report a cross-linkable fluorene derivative, 9,9-bis­(4-vinylbenzyl)-9H-fluorene (SF), copolymerized with the plastic matrix, to facilitate effective Förster resonance energy transfer to boost the light yield. Noncurable 9,9-dimethyl-9H-fluorene (MF) and 9,9′-spirobifluorene (SBF) were also introduced to bridge the energy transfer gap between the polymer matrix and the primary dye. The plastic scintillator comprising 5 wt % SF and 20 wt % MF exhibits a light yield of 11 600 photons/MeV with a scintillation decay time constant of 2.3 ns.

Fast Spectroscopic Gamma Scintillation Using Hafnium Oxide Nanoparticles–Plastic Nanocomposites

“…This is due to the formation of crystalline MF aggregates, which scattered the light. 20 We also found that the cross-linker (i.e., DVB) played an important role in bulk transmittance. Figure S3 shows the transmittance curves of two nanocomposites containing 20% NPs and 20% MF of the same thickness.…”

“…The characteristic decay times are 2.4 ns for the 20% NP nanocomposite and 2.5 ns for the 40% one (Figure 4f and Table S1), which are very close to that of the unloaded nanocomposite (2.3 ns). 20 We conclude that the addition of NPs did not alter the fast scintillation kinetics. It is known that MF participates in the cascade energy transfer via FRET in the conjugated polymer matrix.…”

“…We reported the use of MF in plastic scintillators to enhance exciton production and transfer efficiency. 20 Hence, we first examined the MF effects on light output in the scaled-up nanocomposites (diameter: 17 mm). We prepared monoliths containing 0−30% MF and 0% NPs, and the light output reached a maximum of 10363 ph/MeV at 20% MF loading (Figure S4).…”

“…29 We reported that the addition of MF did not alter the fast decay of plastic scintillators as MF participated in an even faster Forster resonance energy transfer (FRET) process in the cascade energy transfer. 20 Herein, we further studied the scintillation decay time of 20% and 40% NP-loaded nanocomposites using a time-correlated single photon counting (TCSPC) method. Both curves showed a predominantly single exponential decay, indicating that the scintillation light came solely from the POPOP fluorescence.…”

Intra- vs Intermolecular Aurophilic Contacts in Dinuclear Gold(I) Compounds: Impact on the Population of the Triplet Excited State

“…The effect of the chromophore has also been considered, incorporating rigid molecules with planar geometry that could induce inter- or intramolecular interactions such as π···π or C–H···π . The two different chromophores chosen were dibenzofuran, well known to present thermal stability, ,, and 9,9′-dimethylfluorene, well known to have promising potential for the preparation of deep-blue organic light-emitting diodes (OLEDs). − They have been carefully chosen since they present similar expected quantum yield triplet formation, ϕ T (0.39 for dibenzofuran and 0.22–32 for fluorene) . In this way, the effect of the coordination to the gold­(I) atom, the proximity of the two gold­(I) units in the molecule, and the possible establishment of intra- or intermolecular aurophilic contacts can be determined.…”