Transuranium Sulfide via the Boron Chalcogen Mixture Method and Reversible Water Uptake in the NaCuTS₃ Family

Abstract

The behavior of 5f electrons in soft ligand environments makes actinides, and especially transuranium chalcogenides, an intriguing class of materials for fundamental studies. Due to the affinity of actinides for oxygen, however, it is a challenge to synthesize actinide chalcogenides using non-metallic reagents. Using the boron chalcogen mixture method, we achieved the synthesis of the transuranium sulfide NaCuNpS3 starting from the oxide reagent, NpO2. Via the same synthetic route, the isostructural composition of NaCuUS3 was synthesized and the material contrasted with NaCuNpS3. Single crystals of the U-analogue, NaCuUS3, were found to undergo an unexpected reversible hydration process to form NaCuUS3·xH2O (x ≈ 1.5). A large combination of techniques was used to fully characterize the structure, hydration process, and electronic structures, specifically a combination of single crystal, powder, high temperature powder X-ray diffraction, extended X-ray absorption fine structure, infrared, and inductively coupled plasma spectroscopies, thermogravimetric analysis, and density functional theory calculations. The outcome of these analyses enabled us to determine the composition of NaCuUS3·xH2O and obtain a structural model that demonstrated the retention of the local structure within the [CuUS3]− layers throughout the hydration–dehydration process. Band structure, density of states, and Bader charge calculations for NaCuUS3, NaCuUS3·xH2O, and NaCuNpS3 along with X-ray absorption near edge structure, UV–vis–NIR, and work function measurements on ACuUS3 (A = Na, K, and Rb) and NaCuUS3·xH2O samples were carried out to demonstrate that electronic properties arise from the [CuTS3]− layers and show surprisingly little dependence on the interlayer distance.

NaGaSe2: A Water-Loving Multifunctional Non-van der Waals Layered Selenogallate

“…On the other hand, zur Loye’s group has demonstrated the ion exchange capability of NaGaS 2 and the dynamic role of hydration . Recently, zur Loye’s group also demonstrated reversible water uptake in Na-intercalated layered actinide chalcogenides . With this renewed interest in the hydration–dehydration behavior of alkali ion-containing non-vdW layered chalcogenide materials and considering the fact that most of the superionic Na- and Li-ion conductors are from the chalcogenide family, − it is important to study their hydration chemistry and their effect on properties.…”

Advances in Chalcogenide Crystal Growth: Flux and Solution Syntheses, and Approaches for Postsynthetic Modifications

“…The careful selection of a flux enables reactions to take place in the targeted temperature ranges and promotes the formation of different material classes, such as SICs and heteroanionic or heterolayered structures. However, another critical parameter for chalcogenide synthesis is the need to avoid oxygen sources present in the reaction mixture, which has a decidedly negative impact on the reaction outcomes. , Oxygen not only readily reacts with sulfur and sulfides, converting them to oxides, but it can also form stable oxychalcogenides, even when only trace amounts are present in the reaction mixture, e.g., part of the flux or as a contaminant in the starting materials. In some cases, it is challenging to obtain a pure chalcogenide phase due to the presence of oxychalcogenide contaminants in the reagents or due to the presence of unwanted oxygen in the reaction environment leading to an oxychalcogenide product or byproduct. − Hence, it is vital to control the oxygen level in the reaction system, especially in reactions that involve oxyphilic metals, such as lanthanides and actinides, where it is even harder to obtain phase-pure products that are free of oxygen contamination.…”

“…In this case, Rietveld refinement of the resulting powder or other structural characterization techniques are necessary to understand the transformation occurring during postsynthetic modification. Those methods include extended X-ray absorption fine structure spectroscopy (EXAFS), , which informs about the local structure, and electron diffraction or imaging via transmission electron microscopy, − which offers insights into lattice symmetry as well as interatomic or interlayer distances. In this section, we focus on the various techniques that can be used to create new chalcogenide materials starting from single crystals and producing a final product suitable for SC-XRD.…”

“…The driving force of the water intercalation process is a combination of the layered nature of the pristine material and the energetically beneficial hydration of the Na + ions (significant negative hydration enthalpy) . Notably, the [Na 2 Cl]­GaS 2 SIC material, consisting of similar GaS 2 – layers and [Na 2 Cl] + salt inserts, does not undergo hydration, implying that the chalcogenide coordination environment of Na + is also a prerequisite for water intercalation. , Another intriguing example of water intercalation in layered chalcogenides is water uptake in NaCuU Q 3 ( Q = S and Se, space group Cmcm ) and formation of NaCuU Q 3 · x H 2 O ( x ≈ 1.5, space group P 2/ m ) . Similar to the NaGaS 2 · x H 2 O structure, only CuU Q 3 – layers were resolved by SC-XRD, and the formula determination required DFT calculations, TGA, and IR spectroscopy.…”

Tunable Salt-Inclusion Chalcogenides for Ion Exchange, Photoluminescence, and Scintillation

“…Advances in synthetic chalcogenide chemistry have accelerated the discovery of functional materials as well as stimulated the development of numerous technological applications for these materials, all helped by an increased understanding of composition–property relationships. , Chalcogenide-based compounds occupy a unique position in material chemistry due to the soft nature of the chalcogen elements and emerging covalent metal chalcogenide bonding, which results in a rich and diverse crystal chemistry. , In fact, the electronic structure of chalcogenide materials favors their applications as quantum materials, catalysts, ion-exchange materials, ion-conductors, luminophores, thermoelectric materials, and semiconductors. − Recent advances in developing convenient synthetic approaches have enabled the rational synthesis of new functional chalcogenide-based materials containing a wide range of elements, resulting in various material types, ranging from nanoparticles to large single crystals of pure inorganic compositions and hybrid structures. − Another new material type that has emerged from these investigations is salt-inclusion chalcogenide materials (SICs) , that exhibit novel framework topologies and possess ionic inserts (salt-inclusions).…”