We report the successful crystal growth of a previously unknown mixed-metal organic compound (CH3NH3)2AgInBr6.

White-light broadband emission in the visible range from the low-dimensional halide perovskites is commonly attributed to structural distortions in lead bromide octahedra. In this paper, we report Dion–Jacobson-phase two-dimensional (2D) lead bromide perovskites based on short aromatic diammonium cations, p-phenylene diammonium (pPDA), m-phenylene diammonium (mPDA), and two 1D compounds templated by o-phenylene diammonium (oPDA). All of the compounds exhibit white-light emission. Single-crystal X-ray diffraction analysis reveals that the distortion of the Pb octahedra is influenced by the stereochemistry of the cations and their interactions with the perovskite layers. Solid-state 1H and 207Pb NMR spectroscopy analysis further confirms this trend, whereby different 1H and 207Pb chemical shifts are observed for the pPDA and mPDA spacer cations, indicating different hydrogen-bonding interactions and octahedral distortions. Owing to the octahedral distortion, 2D (mPDA)PbBr4 compounds exhibit broader white-light emission than 2D (pPDA)PbBr4. Density functional theory calculations suggest that (pPDA)PbBr4 and (mPDA)PbBr4 are direct-band-gap semiconductors, and they exhibit larger electronic band gaps and effective masses than the Ruddlesden–Popper-phase (BA)2PbBr4. Among the films of these compounds, 2D (mPDA)PbBr4 shows the best stability, which is attributed to stronger hydrogen-bonding interactions in the material.

Removal of chromate (CrO4 2–) and pertechnetate (TcO4 –) from the Hanford Low Activity Waste (LAW) is beneficial as it impacts the cost, life cycle, operational complexity of the Waste Treatment and Immobilization Plant (WTP), and integrity of vitrified glass for nuclear waste disposal. Here, we report the application of [MoIV 3S13]2– intercalated layer double hydroxides (LDH–Mo3S13) for the removal of CrO4 2– as a surrogate for TcO4 –, from ppm to ppb levels from water and a simulated LAW off-gas condensate of Hanford’s WTP. LDH–Mo3S13 removes CrO4 2– from the LAW condensate stream, having a pH of 7.5, from ppm (∼9.086 × 104 ppb of Cr6+) to below 1 ppb levels with distribution constant (K d) values of up to ∼107 mL/g. Analysis of postadsorbed solids indicates that CrO4 2– removal mainly proceeds by reduction of Cr6+ to Cr3+. This study sets the first example of a metal sulfide intercalated LDH for the removal of CrO4 2–, as relevant to TcO4 –, from the simulated off-gas condensate streams of Hanford’s LAW melter which contains highly concentrated competitive anions, namely F–, Cl–, CO3 2–, NO3 –, BO3 3–, NO2 –, SO4 2–, and B4O7 2–. LDH–Mo3S13’s remarkable removal efficiency makes it a promising sorbent to remediate CrO4 2–/TcO4 – from surface water and an off-gas condensate of nuclear waste.

A laboratory experiment is described that introduces second-year undergraduate organic chemistry students to organic electronic materials. The discovery of metallic conductivity in the charge transfer salt tetrathiafulvalene tetracyanoquinodimethane (TTF–TCNQ) is a landmark result in the history of organic electronics. The charge transfer interaction is not only relevant to real-world applications, it also has pedagogical value related to understanding redox chemistry, aromaticity, and conjugation. In this laboratory experiment, students carry out a solution phase synthesis of TTF–TCNQ from the molecular precursors TTF and TCNQ. The product is characterized by infrared spectroscopy. Characteristic changes in absorption frequency are correlated with increased aromatic character and observable lengthening of the nitrile bond. In an optional extension, students experimentally verify the great difference in conductivity between the charge transfer salt and the neutral parent components.

ACuZrQ 3 (A = Rb, Cs; Q = S, Se, Te) were synthesized as black platelet crystals. RbCuZrS 3 , RbCuZrSe 3 , and CsCuZrS 3 crystallize in the KCuZrSe 3 structure type with space group Cmcm, and RbCuZrTe 3 and CsCuZrTe 3 crystallize in the lower symmetry space group Pnma. The tellurides exhibit a secondorder Jahn−Teller distortion with off-centering of Zr in its octahedral environment. The magnitude of the distortion is larger in RbCuZrTe 3 than in CsCuZrTe 3 . The structures of β-CsCuS 4 and Rb 2 Cu 5 Te 5 were also determined. CsCuZrS 3 melts at 910 °C and exhibits partial decomposition upon heating at 275 °C, while CsCuZrTe 3 melts incongruently. Our DFT calculations of RbCuZrQ 3 (Q = S, Se) and CsCuZrS 3 indicate direct gap semiconductors in agreement with experiments. ACuZrTe 3 (A = Rb, Cs) were calculated to be metals which was confirmed for RbCuZrTe 3 with variable temperature conductivity measurements and consistent with heat capacity measurements. Spectroscopic measurements found a bandgap and work function of 1.44(5) eV and 4.89(5) eV for RbCuZrS 3 and 0.95(5) eV and 4.67(5) eV for RbCuZrSe 3 , respectively. RbCuZrTe 3 did not exhibit an optical bandgap and has a work function of 4.64(5) eV. RbCuZrTe 3 exhibits a low thermal conductivity under 0.5 W m −1 K −1 at room temperature.

Topological insulators have been predicted to exhibit a variety of interesting phenomena including a quantized magnetoelectric response and novel spintronics effects due to spin textures on their surfaces. However, experimental observation of these phenomena has proved difficult due to the finite bulk carrier density which may overwhelm the intrinsic topological responses that are expressed at the surface. Here, we demonstrate a novel ionic gel gating technique to tune the chemical potential of Bi2Se3 thin films while simultaneously performing THz spectroscopy. We can tune the carrier concentration by an order of magnitude and shift the Fermi energy, EF to as low as 10 meV above the Dirac point. At high bias voltage and magnetic field, we observe a quantized Faraday angle consistent with the topological magnetoelectric effect that can be tuned by ionic gel gating through a number of plateau states. arXiv:1807.01742v1 [cond-mat.mes-hall]

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Lithium chalcogenides have been understudied, owing to the difficulty in managing the chemical reactivity of lithium. These materials are of interest as potential ion conductors and thermal neutron detectors. In this study, we describe three new cubic lithium copper chalcotitanates that crystallize in the P4̅ 3m space group. LiCu 3 TiS 4 , a = 5.5064(6) Å, and LiCu 3 TiSe 4 , a = 5.7122(7) Å, represent two members of a new stuffed diamond-type crystal structure, while LiCu 3 TiTe 4 , a = 5.9830(7) Å crystallized into a similar structure exhibiting lithium and copper mixed occupancy. These structures can be understood as hybrids of the zinc-blende and sulvanite structure types. In situ powder X-ray diffraction was utilized to construct a "panoramic" reaction map for the preparation of LiCu 3 TiTe 4 , facilitating the design of a rational synthesis and uncovering three new transient phases. LiCu 3 TiS 4 and LiCu 3 TiSe 4 are thermally stable up to 1000 °C under vacuum, while LiCu 3 TiTe 4 partially decomposes when slowly cooled to 400 °C. Density functional theory calculations suggest that these compounds are indirect band gap semiconductors. The measured work functions are 4.77(5), 4.56(5), and 4.69(5) eV, and the measured band gaps are 2.23(5), 1.86(5), and 1.34(5) eV for the S, Se, and Te analogues, respectively.