Scintillators, such as the commercial standard NaI(Tl), are materials that fluoresce when exposed to high energy particles. This property has been important in the development of instruments such as the medical CT scan, X-rays in airport security systems, and even nuclear detection systems. There are a wide range of materials that scintillate, from organic to inorganic to plastic scintillators. Inorganic crystal scintillators consist of a wide range of materials, including alkali metal halides, lanthanum halides, metal oxides, and metal-silicates (MSiOx). For the M-SiO2 optimized inorganic scintillators their fluorescent properties can be further improved through the doping with lanthanide cations. Original synthetis using metal siloxide [M(OSi(OR)3)x] precursors have had varying success in converting to the MSiOx-based materials. Interest in alternative ligands lead to us to studying tris(trimethylsilyl)silanol (or H-SST). The H-SST ligand was of interest due to its favorable decomposition properties (i.e., silicon-silicon bonds (Si-Si 54 kcal/mol) have considerably lower dissociation energies than the silicon-carbon bonds (Si-C 92.5 kcal/mol)); therefore, upon processing it might be possible to generate the MSiOx fluorescent materials. Metal alkoxides ([M(OR)x]) are excellent precursors to ceramic materials and can be modified by altering their ligand set. Consequently, the combination of H-SST and [M(OR)x] precursors may increases the potential for producing a single-source precursor to MSiOx scintillators. In previous research performed in the Boyle group at Sandia National Laboratories, a series of Group 4 [M(OR)4] were modified with the H-SST ligand and processed by thermally heating them in air. The product formed was a core/shell nanomaterial, in which the metal core was surrounded by a silica based matrix or a silica core was surrounded by a metal-based matrix. Even though the SST successfully bound to the metals, when exposed to radiation the molecules and the products did not luminesce. In order to synthesize scintillators with higher sensitivity different metals must be considered. Due to the previous success with the lanthanide metals in the production of scintillators, combining these metals with the H-SST ligand could prove an interesting alternative to producing metal silica based scintillators. This work will present the synthesis, characterization, and materials properties of a series of [Ln(SST)3(solv)2] molecules that were generated.

Synthesis and characterization of lanthanide-silica based core/shell nanoparticles for scintillator applications

2019 Spring National Meeting

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