Nanocomposite Scintillators Loaded With Hafnium Oxide and Phosphorescent Host and Guest for Gamma Spectroscopy.

Gamma sensitive plastic scintillators are of critical importance in the fields of nuclear nonproliferation, medical imaging, and high energy physics. However, there is often a trade-off between high light yield and high loading of high-Z components, both of which play an essential role in gamma ray detection. This work takes advantage of triplet exciton harvesting to increase gamma light yield by utilizing 1,3-di(9H-carbazol-9-yl)benzene and 9,9-dimethyl-9H-fluorene as triplet hosts to facilitate Dexter energy transfer to bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrPic), a blue light emitting phosphorescent dye. A plastic scintillator containing 20 wt % MF, 10 wt % mCP, and 2 wt % FIrPic has a high gamma light yield of 14 800 Ph/MeV. Incorporating 20-35 wt % hafnium oxide nanoparticles into this organic matrix results in nanocomposites that demonstrate a gamma photopeak energy resolution of 6.4-9.7% at 662 keV while still retaining a high gamma light yield between 8800 and 10 800 Ph/MeV.

Hybrid Fabrication of Prestrain-Locked Acrylic Dielectric Elastomer Thin Films and Multilayer Stacks.

Dielectric elastomers based on commercial acrylic dielectric elastomers (VHB adhesive films) are widely investigated for soft actuators due to their large electrically driven actuation strain and high work density. However, the VHB films require prestretching to overcome electromechanical instability, which adds fabrication complexity. In addition, their high viscoelasticity leads to a low response speed. Interpenetrated polymer networks (IPNs) are developed to lock the prestrain in VHB films, resulting in free-standing films that are capable of large-strain actuation. In this work, a prestrain-locked high-performance dielectric elastomer thin film (VHB-IPN-P) by introducing 1,6-hexanediol diacrylate to create an IPN in the VHB network and a plasticizer to enhance the actuation speed is reported. VHB-IPN-P based actuators exhibit stable actuation at 60% strain up to 10 Hz and reach a peak energy density of 102 J kg⁻1 . In addition, a hybrid process is also developed for the fabrication of multilayer stacks of VHB-IPN-P with strong inter-layer bonding and structural integrity. Four-layer stacks fabricated preserve the strain and energy density of single-layer VHB-IPN-P films but with linearly scaled force and work output.