Crystal Growth & Design最新文献

Radiation detection (dosimetry) most commonly uses scintillating materials in a wide array of fields, ranging from energy to medicine. Scintillators must be able to not only fluoresce owing to the presence of a suitable chromophore but also withstand damage from radiation over prolonged periods of time. While it is inevitable that radiation will cause damage to the physical and chemical properties of materials, there is limited understanding of features within solid-state scintillators that afford increased structural integrity upon exposure to gamma (γ) radiation. Even fewer studies have evaluated both physical- and atomistic-level properties of organic solid-state materials. Previous work demonstrated cocrystalline materials afford radiation resistance in comparison to the single component counterparts, as realized by trans-1,2-bis(4-pyridyl)ethylene (4,4'-bpe). To support the rational design of radiation-resistant scintillators, we have examined all symmetric and unsymmetric isomers of trans-1-(n-pyridyl)2-(m-pyridyl)ethylene (n,m'-bpe, where n and/or m = 2, 3, or 4) solid-state crystalline materials. Experimental methods employed include single-crystal, powder, and electron diffraction as well as solid-state fluorimetry. Periodic density functional theory (DFT) calculations were used to understand the atomistic-level differences in bond lengths, bond orders, and packing. Electron diffraction was also utilized to determine the structure of a nanocrystalline sample. The results provide insights into possible trends involving factors such as molecular symmetry which provides radiation resistance as well as information for rationally designing single and multicomponent scintillators with the intent of minimizing changes upon γ-radiation exposure.

In this work, we present a theoretical investigation of the SrTiO₃ perovskite-supported Pd catalyst in the methanol electro-oxidation reaction. In order to determine the metal-support interactions, we designed a system consisting of a Pd (100) double layer supported on one of the two possible terminations of the (100) perovskite surface. These terminations are characterized by different reducibilities of the layers directly interacting with the Pd bilayer and result in the difference in the stability of the surface-bound intermediates. Despite the fact that the Pd surface is identical in terms of geometry, we observed significant differences in the overpotential required for the reaction; in the case of TiO₂ termination, the overpotential has been determined to be 0.68 V, while in the case of SrO termination, it amounts to as much as 1.35 V. We further investigate the charge transfers within the components of the system and the geometries of the intermediates to unravel the role of the electron structure on the overall efficiency of the process.

The initial use of 2-(pyridin-2-yl)propane-1,3-diol (pypdH₂) in Mn cluster chemistry has afforded two new mixed-valence polynuclear Mn clusters, namely, [Mn₈Ο₅(pypd)(hmp)₃(O₂CCMe₃)₈] (1) and [Mn₁₆Ο₁₀(N₃)₂(pypd)₂{(py)₂CO₂}₄(O₂CEt)₁₂] (2) (hmp^- = deprotonated 2-hydroxymethylpyridine; (py)₂CO₂ ^2- = deprotonated gem-diol form of di-2-pyridyl ketone). Compound 1 features a novel [Mn^III ₇Mn^II(μ₄-O)₂(μ₃-O)₃(μ-OR)₅]⁸⁺ structural core resembling a supertetrahedron T3, lacking two apexes, while complex 2 has a [Mn^III ₁₄Mn^II ₂(μ₄-O)₄(μ₃-O)₆(μ-N₃)₂(μ₃-OR)₂(μ-OR)₈]¹⁴⁺ core consisting of two [Mn₈] subunits related to 1 and thus is a dimeric analogue of 1. Direct current (dc) magnetic susceptibility studies revealed the presence of dominant antiferromagentic exchange interactions between the Mn ions in complexes 1 and 2 and small ground state spin values for both compounds. Overall, this work highlights the capability of polyol-like chelates like pypdH₂ to stabilize high nuclearity 3d metal clusters based on polynuclear building blocks.