Scintillators based on Tl salts that provide high densities and high effective atomic numbers are currently being investigated for their possible use in radioisotope identification applications. Ce-doped Tl2LaCl5, in particular, has been the leading compound of those studied, showing good light output and energy resolution. The analogous Tl2CeCl5 has received much less attention, and the information known about it is rather incomplete. This paper focuses on the scintillation and optical properties of Tl2CeCl5 single crystals and compares them to those of Tl2LaCl5:Ce to better evaluate the effect of full substitution of La with Ce.

Li-containing elpasolite scintillators are currently investigated for their ability to detect both thermal neutrons and gamma photons with a single inorganic crystal. The scintillation is typically triggered by using an activator such as Ce. However, when Tl, also a luminescent ion, is present in the matrix, competition between the two centers Tl and Ce can occur. In this study, we are using Ce doped Tl2LiYCl6 to investigate this competition. To this end, the Ce (which substitutes Y) concentration is varied from 0 to 1 in the Tl2LiY1-xCexCl6 composition. In the low concentration range in which Ce remains a dopant, the photo- and radioluminescence spectra show that the scintillation of Tl2LiYCl6:Ce is mostly dominated by recombination on intrinsic luminescent centers. For cerium concentrations higher than x = 0.02, very different emissions can be easily distinguished from the photo- and radioluminescence of undoped and low Ce doped Tl2LiYCl6 crystals. These emissions are attributed to the formation of a second phase Tl2CeCl5, identified by X-ray diffraction. We conclude that the intrinsic luminescence related to Tl dominates the scintillation in the range of concentration for which Ce does substitute on the Y-site.

Water-based liquid scintillators (WbLS) present an attractive target medium for large-scale detectors with the ability to enhance the separation of Cherenkov and scintillation signals from a single target. This work characterizes the scintillation properties of WbLS samples based on LAB/PPO liquid scintillator (LS). X-ray luminescence spectra, decay profiles, and relative light yields are measured for WbLS of varying LS concentration as well as for pure LS with a range of PPO concentrations up to 90 g L-1. The scintillation properties of the WbLS are related to the precursor LAB/PPO: starting from 90 g L-1PPO in LAB before synthesis, the resulting WbLS have spectroscopic properties that instead match 10 g L-1 PPO in LAB. This could indicate that the concentration of active PPO in the WbLS samples depends on their processing.

The title compound, thallium magnesium trichloride, has been identified as a scintillator with both moderate gamma-stopping power and moderate light yield. Knowledge of its crystal structure is needed for further development. This work determines the crystal structure of TlMgCl₃ to be hexa-gonal P6₃/mmc (No. 194) and isostructural with RbMgCl₃, contrary to previously reported data. This structure was obtained by single-crystal X-ray diffraction and was further confirmed by neutron diffraction measurements. Extending neutron diffraction measurements to high temperature, the data show that TlMgCl₃ maintains this crystal structure from 290 K up through 725 K, approaching the melting point of 770 K. Anisotropic thermal expansion coefficients increase over this temperature range, from 31 to 38 × 10^-6 K^-1 along the a axis and from 19 to 34 × 10^-6 K^-1 along the c axis.

We have synthesized several morphologies and crystal structures of MgWO₄ using a one-pot hydrothermal method, producing not only monoclinic stars and large nanoparticles but also triclinic wool balls and sub-10 nm nanoparticles. Herein we describe the importance of reaction parameters in demonstrating morphology control of as-prepared MgWO₄. Moreover, we correlate structure and composition with the resulting photoluminescence and radioluminescence properties. Specifically, triclinic-phase samples yielded a photoluminescence emission of 421 nm, whereas monoclinic-phase materials gave rise to an emission maximum of 515 nm. The corresponding radioluminescence data were characterized by a broad emission peak, located at 500 nm for all samples. Annealing the wool balls and sub-10 nm particles to transform the crystal structure from a triclinic to a monoclinic phase yielded a radioluminescence (RL) emission signal that was two orders of magnitude greater than that of their unannealed counterparts. Finally, to confirm the practical utility of these materials for biomedical applications, a series of sub-10 nm particles, including as-prepared and annealed samples, were functionalized with biocompatible PEG molecules, and subsequently were found to be readily taken up by various cell lines as well as primary cultured hippocampal neurons with low levels of toxicity, thereby highlighting for the first time the potential of this particular class of metal oxides as viable and readily generated platforms for a range of biomedical applications.