Denisse Ortiz-Acosta

Large-scale synthesis of CexLa1−xF3 nanocomposite scintillator materials

Transparent nanocomposites have been developed which consist of nanocrystals embedded in an organic matrix. The materials are comprised of up to 60% by volume of 7–13 nm crystals of the phosphor CexLa1−xF3, and are greater than 70% transparent in the visible region at a thickness of 1 cm. Consistencies of the nanocomposites range from a solid polymer to a wax to a liquid, depending on the workup conditions of the nanoparticle synthesis. These transparent nanophosphor composite materials have potential applications in radiation detection as scintillators, as well as in other areas such as imaging and lighting, and can be produced on large scales up to near-kilogram quantities at near ambient conditions, much lower in temperature than typical nanoparticle syntheses.

Luminescence in CeIV polyoxometalate [Ce(W5O18)2]8-: a combined experimental and theoretical study

Herein we describe the unique luminescent behavior observed in [Ce(IV)(W(5)O(18))(2)](8-) clusters and examine the photophysical properties using density functional theory.

Ionic Liquid Polyoxometalates as Light Emitting Materials

The low melting point, negligible vapor pressure, good solubility, and thermal and chemical stability make ionic liquids useful materials for a wide variety of applications. Polyoxometalates are early transition metal oxygen clusters that can be synthesized in many different sizes and with a variety of heterometals. The most attractive feature of POMs is that their physical properties, in particular electrical, magnetic, and optical properties, can be easily modified following known procedures. It has been shown that POMs can exhibit cooperative properties, as superconductivity and energy transfer. POM ionic liquids can be obtained by selecting the appropliate cation. Different alkyl ammonium and alkyl phosphonium salts are being used to produce new POM ionic liquids together with organic or inorganic luminescent centers to design light emitting materials. Ammonium and phosphonium cations with activated, polymerizable groups are being used to further polymerize the ionic liquid into transparent, solid materials with high metal density.

Isolation of an Asymmetric Lanthanide Polyoxometalate, Na12H[(W5O18)Tb(H2W11O39)]·42H2O, Containing Two Distinct Isopolyanions

The structural characterization of a new, asymmetric polyoxoanion, Na12H[(W5O18)Tb(H2W11O39)]·42H2O, is reported herein. This new structure was isolated from a mixture of a number of compounds, including the symmetric Na9[Tb(W5O18)2] sandwich cluster, and the lanthanide-free cluster, Na10(H2W12O42). The major product of the reaction was Na9[Tb(W5O18)2], and the compound reported here is a minor product that is obtained reproducibly. The salts of these three clusters do not differ significantly in their crystal habit, size, and color. The crystal structure of Na12H[(W5O18)Tb(H2W11O39)]·42H2O was determined by single-crystal X-ray diffraction and shows that the cluster is composed of a lacunary Lindqvist (W5O18)6− building block and an unusual lacunary metatungstate (H2W11O39)10− polyanion connected through a central Ln3+ cation. The central Tb3+ cation has a square antiprismatic symmetry, the lacunary metatungstate has a square pyramidal symmetry, and the lacunary Lindqvist polyanion exhibits a cuboctahedral symmetry. This is the first example of a crystallographically characterized sandwich cluster possessing a lacunary metatungstate (H2W11O39)10− ligand.Graphical Abstract

New Experimental Data in DC745U

The objectives of this project are: (1) study the molecular and mechanical properties of DC745U - (a) DC745U is a silicone elastomer used in several weapons systems, (b) depending on their chemistry and formulation, polymers can be susceptible to damage and failures due to weak chemical linkages and physical interactions, (c) inefficient production processes can generate heterogeneities throughout the material that can contribute negatively to the overall performance and lifetime of the polyer, (d) aging, long-term thermal and radioactive conditions, and mechanical strains can affect the materials network structure and contribute to the degradation of the production; (2) characterization of DC745U materials cured under different conditions to determine possible differences to the polymer structure; and (3) this work is relevant to mission-critical programs and for supporting programmatic work for weapon research.