In situ Investigations of the Formation Mechanism of Metastable γ-BiPd Nanoparticles in Polyol Reductions.

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

Na2Fe2Se2O: a double anti-perovskite with prevalence of anionic redox activity in Na-ion batteries.

Na2Fe2Se2O with the I4/mmm space group was studied in sodium-ion batteries, delivering a reversible specific capacity of more than 140 mA h g-1. Operando XRD and XAS studies disclosed bifunctional redox behaviour with the prevalence of anionic electrochemical activity and a likely partial decomposition of the material, which, however, does not influence the electrochemical behaviour of the system.

Electron spin resonance study on the 4fhoneycomb quantum magnet YbCl3.

The local magnetic properties of Yb3+in the layered honeycomb material YbCl3were investigated by electron spin resonance on single crystals. For in-plane and out-of-plane field orientations theg-factor shows a clear anisotropy (g∥=2.97(8)andg⊥=1.53(4)), whereas the low temperature exchange coupling and the spin relaxation display a rather isotropic character. At elevated temperatures the contribution of the first excited crystal field level (21±2meV) dominates the spin relaxation.

Unconventional Spin State Driven Spontaneous Magnetization in a Praseodymium Iron Antimonide.

Consolidating a microscopic understanding of magnetic properties is crucial for a rational design of magnetic materials with tailored characteristics. The interplay of 3d and 4f magnetism in rare-earth transition metal antimonides is an ideal platform to search for such complex behavior. Here the synthesis, crystal growth, structure, and complex magnetic properties are reported of the new compound Pr3 Fe3 Sb7 as studied by magnetization and electrical transport measurements in static and pulsed magnetic fields up to 56 T, powder neutron diffraction, and Mößbauer spectroscopy. On cooling without external magnetic field, Pr3 Fe3 Sb7 shows spontaneous magnetization, indicating a symmetry breaking without a compensating domain structure. The Fe substructure exhibits noncollinear ferromagnetic order below the Curie temperature TC  ≈ 380 K. Two spin orientations exist, which approximately align along the Fe-Fe bond directions, one parallel to the ab plane and a second one with the moments canting away from the c axis. The Pr substructure orders below 40 K, leading to a spin-reorientation transition (SRT) of the iron substructure. In low fields, the Fe and Pr magnetic moments order antiparallel to each other, which gives rise to a magnetization antiparallel to the external field. At 1.4 K, the magnetization approaches saturation above 40 T. The compound exhibits metallic resistivity along the c axis, with a small anomaly at the SRT.

In situ investigation of the formation mechanism of α-Bi2Rh nanoparticles in polyol reductions.

The synthesis of intermetallic phases formed from elements with very different melting points is often time and energy consuming, and in extreme cases the evaporation of a reactant may even prevent formation completely. An alternative, facile synthesis approach is the reduction of metal salts in the polyol process, which requires only moderate temperatures and short reaction times. In addition, the starting materials for this procedure are readily available and do not require any special treatment to remove or prevent passivation layers, for example. Although the formation of intermetallic particles via the polyol process is an established method, little attention has been paid to the mechanism behind it. However, it is precisely a deeper understanding of the underlying mechanisms that would enable better and more targeted synthesis planning and product design. Taking the well-known formation of Bi2Rh particles from Bi(NO3)3 and various rhodium salts in ethylene glycol as an example, we studied the chemical process in detail. We investigated the effects of anion type and pH on the polyol reaction. The reaction was also probed by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by X-ray and electron diffraction, electron microscopy and optical spectroscopy. In the first step, co-reduction of the metal cations leads to BiRh. Only with increasing reaction temperature, the remaining bismuth cations in the solution are reduced and incorporated into the BiRh particles, leading to a gradual transition from BiRh to α-Bi2Rh.

Crystal structure of potassium orthoselenate(IV), K2SeO3.

Crystal structure data for potassium orthoselenate(IV), K2SeO3, are reported for the first time. Colorless, block-shaped crystals were grown in a potassium hydro-flux, i.e. under ultra-alkaline conditions, within 10 h. K2SeO3 crystallizes isostructural with Na2SO3 and K2TeO3 in the trigonal space group P with lattice parameters a = 6.1063 (4) Šand c = 6.9242 (4) Šat 100 (1) K. In the trigonal-pyramidal, C 3v-symmetric [SeO3]2- anion, the bond length is 1.687 (1) Å, and the bond angle is 103.0 (1)°. Two of the three unique potassium cations exhibit a coordination number of six, and the third a coordination number of nine.

LaTe1.9: a tenfold superstructure of the ZrSSi type.

Single crystals of LaTe1.9 (lanthanum telluride) have been obtained by chemical transport reactions with iodine as transport agent. LaTe1.9 adopts the CeSe1.9 structure type and crystallizes in the space group P42/n with lattice parameters a = 10.1072 (3) Šand c = 18.2874 (6) Å. The crystal structure comprises an alternating stacking of puckered [LaTe] slabs and planar [Te] layers along [001]. The planar [Te] layer is dominated by dumbbell-shaped Te2 2- anions along an isolated Te2- anion and a vacancy. The Te2 2- anions form an eight-membered ring enclosing the vacancy in the centre.

Correction: On the importance of π-hole spodium bonding in tricoordinated HgII complexes.

Correction for 'On the importance of π-hole spodium bonding in tricoordinated HgII complexes' by Ghodrat Mahmoudi et al., Dalton Trans., 2020, 49, 17547-17551, https://doi.org/10.1039/D0DT03938A.

One-pot synthesis of brewer's spent grain-supported superabsorbent polymer for highly efficient uranium adsorption from wastewater.

High-efficient and fast adsorption of uranium is important to reduce the hazards caused by the uranium contamination of water environment due to the increased human activities. Herein, brewer's spent grain (BSG)-supported superabsorbent polymers (SAP) with different cross-linking densities are prepared as cheap and eco-friendly adsorbents for the first time via one-pot swelling and graft polymerization. A 7 wt% NaOH solution is used to swell BSG before grafting and subsequently neutralize the acrylic acid to control the reaction rate without producing alkaline wastewater. Compared with the traditional methods, swelling improves the grafting density and the utilization of raw materials due to the increased disorder degree of the BSG fibers. This results in the grafting of abundant carboxyl and amide groups onto the BSG backbone, forming a strongly hydrophilic polymer network of the BSG-SAP. Compared with the reference polymers without BSG, BSG-SAP presents higher adsorption capacity and enhanced reusability. The highly cross-linked BSG-SAP (BSG-SAP-H) shows an outstanding adsorption capacity of U(VI) (1465 mg/g at pH0 = 4.6), a fast adsorption rate (81% of equilibrium adsorption capacity in 15 min), and a high selectivity in the presence of competing ions. Adsorption mechanism studies reveal the involvement of amide groups, a bidentate binding structure between UO22+ and the carboxyl groups, and a cation exchange between Na+ and UO22+. More importantly, the adsorption capacity of BSG-SAP-H reaches 254.4 mg/g in the fixed-bed column experiment at a low initial concentration (c0(U) = 30 mg/L) and keeps 80% of the adsorption capacity after four cycles, indicating a great potential for uranium removal from wastewater. This work shows a suitable approach to explore the untreated biomass to prepare SAP with enhanced adsorption performance via a general and low-cost strategy.

Coexistence of Tellurium Cations and Anions in Phosphonium-Based Ionic Liquids.

Elemental tellurium readily dissolves in ionic liquids (ILs) based on tetraalkylphosphonium cations even at temperatures below 100 °C. In the case of ILs with acetate, decanoate, or dicyanamide anions, dark red to purple colored solutions form. A study combining NMR, UV-Vis and Raman spectroscopy revealed the formation of tellurium anions (Ten )2- with chain lengths up to at least n=5, which are in dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an ionic liquid reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. Although the spectroscopic detection of tellurium cations in these solutions is difficult, the coexistence of tellurium cations, such as (Te4 )2+ and (Te6 )4+ , and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient to stabilize both types of tellurium ions in solution.

Formation of Bi2Ir nanoparticles in a microwave-assisted polyol process revealing the suboxide Bi4Ir2O.

Intermetallic phases are usually obtained by crystallization from the melt. However, phases containing elements with widely different melting and boiling points, as well as nanoparticles, which provide a high specific surface area, are hardly accessible via such a high-temperature process. The polyol process is one option to circumvent these obstacles by using a solution-based approach at moderate temperatures. In this study, the formation of Bi2Ir nanoparticles in a microwave-assisted polyol process was investigated. Solutions were analyzed using UV-Vis spectroscopy and the reaction was tracked with synchrotron-based in situ powder X-ray diffraction (PXRD). The products were characterized by PXRD and high-resolution transmission electron microscopy. Starting from Bi(NO3)3 and Ir(OAc)3, the new suboxide Bi4Ir2O forms as an intermediate phase at about 160 °C. Its structure was determined by a combination of PXRD and quantum-chemical calculations. Bi4Ir2O decomposes in vacuum at about 250 °C and is reduced to Bi2Ir by hydrogen at 150 °C. At about 240 °C, the polyol process leads to the immediate reduction of the two metal-containing precursors and crystallization of Bi2Ir nanoparticles.

Recycling of Brewer's Spent Grain as a Biosorbent by Nitro-Oxidation for Uranyl Ion Removal from Wastewater.

Developing biosorbents derived from agro-industrial biomass is considered as an economic and sustainable method for dealing with uranium-contaminated wastewater. The present study explores the feasibility of oxidizing a representative protein-rich biomass, brewer's spent grain (BSG), to an effective and reusable uranyl ion adsorbent to reduce the cost and waste generation during water treatment. The unique composition of BSG favors the oxidation process and yields in a high carboxyl group content (1.3 mmol/g) of the biosorbent. This makes BSG a cheap, sustainable, and suitable raw material independent from pre-treatment. The oxidized brewer's spent grain (OBSG) presents a high adsorption capacity of U(VI) of 297.3 mg/g (c 0(U) = 900 mg/L, pH = 4.7) and fast adsorption kinetics (1 h) compared with other biosorbents reported in the literature. Infrared spectra (Fourier transform infrared), 13C solid-state nuclear magnetic resonance spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis were employed to characterize the biosorbents and reveal the adsorption mechanisms. The desorption and reusability of OBSG were tested for five cycles, resulting in a remaining adsorption of U(VI) of 100.3 mg/g and a desorption ratio of 89%. This study offers a viable and sustainable approach to convert agro-industrial waste into effective and reusable biosorbents for uranium removal from wastewater.

Stripe-yzmagnetic order in the triangular-lattice antiferromagnet KCeS2.

Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO2, NaYbS2, and NaYbSe2, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeS2exhibits magnetic order belowTN= 400 mK, which was so far identified only in thermodynamic measurements. Here we reveal the magnetic structure of this long-range ordered phase using magnetic neutron diffraction. We show that it represents the so-called 'stripe-yz' type of antiferromagnetic order with spins lying approximately in the triangular-lattice planes orthogonal to the nearest-neighbor Ce-Ce bonds. No structural lattice distortions are revealed belowTN, indicating that the triangular lattice of Ce3+ions remains geometrically perfect down to the lowest temperatures. We propose an effective Hamiltonian for KCeS2, based on a fit to the results ofab initiocalculations, and demonstrate that its magnetic ground state matches the experimental spin structure.

Structural Variations and Bonding Analysis of the Rare-Earth Metal Tellurides RETe1.875±Î´ (RE = Ce, Pr, Sm, Gd; 0.004 ≤ δ ≤ 0.025).

Crystals of RETe1.875±Î´ (RE = Ce, Pr, Sm, Gd; 0.004 ≤ δ ≤ 0.025) were grown using alkali halide flux and chemical transport reactions. The crystal structures are described in space group Amm2 (no. 38), with lattice parameters of a = 13.3729(5) Å, b = 17.7918(5) Å, c = 18.1561(4) Å for CeTe1.87(1) (T = 100 K), a = 13.271(2) Å, b = 17.747(3) Å, c = 18.160(3) Å for PrTe1.85(1) (T = 100 K), a = 13.1251(6) Å, b = 17.4269(8) Å, c = 17.8808(8) Å for SmTe1.87(1) (T = 100 K), and a = 13.1762(4) Å, b = 17.4995(5) Å, c = 17.9591(5) Å for GdTe1.88(1) (T = 296 K). The structures contain alternating stacks of puckered [RETe] slabs and planar [Te] layers. The latter are composed of small anionic entities, such as Te2- and Te22-, along with a large anionic eight-membered Te ring, as supported by electron localizability indicator-based bond analysis for an ordered model of GdTe1.875. Slightly different patterns for individual compounds indicate a considerable structural flexibility. Temperature-dependent resistance measurements confirm semiconducting behavior for PrTe1.875±Î´ and GdTe1.875±Î´ (magnetic data evidence RE3+ and an antiferromagnetic transition at TN = 4 K for CeTe1.875±Î´ and TN = 11 K for GdTe1.875±Î´), whereas PrTe1.875±Î´ and SmTe1.875±Î´ show no long-range order down to 2 K.

Potassium Ion Conductivity in the Cubic Labyrinth of a Piezoelectric, Antiferromagnetic Oxoferrate(III) Tellurate(VI).

Orange-colored crystals of the oxoferrate tellurate K12+6x Fe6 Te4-x O27 [x=0.222(4)] were synthesized in a potassium hydroxide hydroflux with a molar water-base ratio n(H2 O)/n(KOH) of 1.5 starting from Fe(NO3 )3 ⋅ 9H2 O, TeO2 and H2 O2 at about 200 °C. By using (NH4 )2 TeO4 instead of TeO2 , a fine powder consisting of microcrystalline spheres of K12+6x Fe6 Te4-x O27 was obtained. K12+6x Fe6 Te4-x O27 crystallizes in the acentric cubic space group I 4 ‾ 3d. [FeIII O5 ] pyramids share their apical atoms in [Fe2 O9 ] groups and two of their edges with [TeVI O6 ] octahedra to form an open framework that consists of two loosely connected, but not interpenetrating, chiral networks. The flexibility of the hinged oxometalate network manifests in a piezoelectric response similar to that of LiNbO3 .The potassium cations are mobile in channels that run along the <111> directions and cross in cavities acting as nodes. The ion conductivity of cold-pressed pellets of ball-milled K12+6x Fe6 Te4-x O27 is 2.3×10-4 S ⋅ cm-1 at room temperature. Magnetization measurements and neutron diffraction indicate antiferromagnetic coupling in the [Fe2 O9 ] groups.

Inorganic Synthesis Based on Reactions of Ionic Liquids and Deep Eutectic Solvents.

Ionic liquids and deep eutectic solvents are of growing interest as solvents for the resource-efficient synthesis of inorganic materials. This Review covers chemical reactions of various deep eutectic solvents and types of ionic liquids, including metal-containing ionic liquids, [BF4 ]- - or [PF6 ]- -based ionic liquids, basic ionic liquids, and chalcogen-containing ionic liquids. Cases in which cations, anions, or both are incorporated into the final products are also included. The purpose of this Review is to raise caution about the chemical reactivity of ionic liquids and deep eutectic solvents and to establish a guide for their proper use.

Low Temperature Activation of Tellurium and Resource-Efficient Synthesis of AuTe2 and Ag2 Te in Ionic Liquids.

The low temperature syntheses of AuTe2 and Ag2 Te starting from the elements were investigated in the ionic liquids (ILs) [BMIm]X and [P66614 ]Z ([BMIm]+ =1-butyl-3-methylimidazolium; X = Cl, [HSO4 ]- , [P66614 ]+ = trihexyltetradecylphosphonium; Z = Cl- , Br- , dicyanamide [DCA]- , bis(trifluoromethylsulfonyl)imide [NTf2 ]- , decanoate [dec]- , acetate [OAc]- , bis(2,4,4-trimethylpentyl)phosphinate [BTMP]- ). Powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy revealed that [P66614 ]Cl is the most promising candidate for the single phase synthesis of AuTe2 at 200 °C. Ag2 Te was obtained using the same ILs by reducing the temperature in the flask to 60 °C. Even at room temperature, quantitative yield was achieved by using either 2 mol % of [P66614 ]Cl in dichloromethane or a planetary ball mill. Diffusion experiments, 31 P and 125 Te-NMR, and mass spectroscopy revealed one of the reaction mechanisms at 60 °C. Catalytic amounts of alkylphosphanes in commercial [P66614 ]Cl activate tellurium and form soluble phosphane tellurides, which react on the metal surface to solid telluride and the initial phosphane. In addition, a convenient method for the purification of [P66614 ]Cl was developed.

Freestanding Nanolayers of a Wide-Gap Topological Insulator through Liquid-Phase Exfoliation.

The layered salt Bi14 Rh3 I9 is a weak three-dimensional (3D) topological insulator (TI), that is, a stack of two-dimensional (2D) TIs. It has a wide non-trivial band gap of 210 meV, which is generated by strong spin-orbit coupling, and possesses protected electronic edge-states. In the structure, charged layers of ∞ 2 [ (Bi4 Rh)3 I]2+ honeycombs and ∞ 1 [ Bi2 I8 ]2- chains alternate. The non-trivial topology of Bi14 Rh3 I9 is an inherent property of the 2D intermetallic fragment. Here, the exfoliation of Bi14 Rh3 I9 was performed using two different chemical approaches: (a) through a reaction with n-butyllithium and poly(vinylpyrrolidone), (b) through a reaction with betaine in dimethylformamide at 55 °C. The former yielded few-layer sheets of the new compound Bi12 Rh3 I, while the latter led to crystalline sheets of Bi14 Rh3 I9 with a thickness down to 5 nm and edge-lengths up to several ten microns. X-ray diffraction and electron microscopy proved that the structure of Bi14 Rh3 I9 remained intact. Thus, it was assumed that the particles are still TIs. Dispersions of these flakes now allow for next steps towards the envisioned applications in nanoelectronics, such as the study of quantum coherence in deposited films, the combination with superconducting particles or films for the generation of Majorana fermions, or studies on their behavior under the influence of magnetic or electric fields or in contact with various materials occurring in devices. The method presented generally allows to exfoliate layers with high specific charges and thus the use of layered starting materials beyond van der Waals crystals.

On the importance of π-hole spodium bonding in tricoordinated HgII complexes.

A new coordination polymer [Hg(LI)I]n (1) and a new discrete coordination complex [Hg(HLII)I2] (2) are synthesized and X-ray characterized. The existence of positive π-holes at the spodium atoms in both compounds is evidenced by DFT calculations. In 1, a Hg-S semicoordination bond and a HgI spodium bond are formed at opposite sides of the π-hole. In 2, two different HgI spodium bonds are formed at both sides of the π-hole. This is the first study describing structure-guiding π-hole spodium bonding.

Distorted Te nets in the modulated crystal structures of RETe1.94(1) (RE = La, Pr, Nd).

The two-dimensionally incommensurately modulated crystal structures of the compounds RETe1.94(1) (RE = La, Pr, Nd) were investigated by single-crystal X-ray diffraction. The compounds crystallize in the tetragonal superspace group P4/n(αß½)00(-ßα½)00 (No. 85.2.58.2) with q1 = αa*+ßb*+½c* and q2 = -ßa*+αb*+½c* and share a common motif of an alternating stacking of a puckered [RETe] layer and a planar [Te] layer. This basic structural motif is observed for all reported compounds with unusually large anisotropic displacement parameters in the planar [Te] layer. Taking the modulation into account, a distortion from this perfect square planar net is noted along with vacancies in the planar [Te] layer. The distortion leads to the formation of different discrete anions, like Te2-, Te22- and Te32-, similar to previously reported structures for REX2-δ compounds (RE = trivalent rare earth metal, X = S, Se, Te). The Te-Te distances in the modulated [Te] layer are found in a narrow range as compared to those in the corresponding sulfides and selenides.