Search

The kagom\'e metals RbTi$_3$Bi$_5$ and CsTi$_3$Bi$_5$ were synthesized both as polycrystalline powders by heating the elements an argon atmosphere and as single crystals grown using a self-flux method. The compounds crystallize in the hexagonal crystal system isotypically to KV$_3$Sb$_5$ (P6/mmm, Z = 1, CsTi3Bi5: a = 5.7873(1) {\AA}, c = 9.2062(1) {\AA}; RbTi3Bi5: a = 5.773(1) {\AA}, c = 9.065(1) {\AA}). Titanium atoms form a kagom\'e net with bismuth atoms in the hexagons as well as above and below the triangles. The alkali metal atoms are coordinated by 12 bismuth atoms and form AlB$_2$-like slabs between the kagom\'e layers. Magnetic susceptibility measurements with CsTi$_3$Bi$_5$ and RbTi$_3$Bi$_5$ single crystals reveal Pauli-paramagnetism and traces of superconductivity caused by CsBi$_2$/RbBi$_2$ impurities. Magnetotransport measurements reveal conventional Fermi liquid behavior and quantum oscillations indicative of a single dominant orbit at low temperature. DFT calculations show the characteristic metallic kagom\'e band structure similar to that of CsV$_3$Sb$_5$ with reduced band filling. A symmetry analysis of the band structure does not reveal an obvious and unique signature of a nontrivial topology., Comment: 20 pages, 5 Figures, submitted

We report the synthesis and characterization of a 2D coordination polymer composed of a dianionic perhydroxylated boron cluster, [B12(OH)122−], coordinated to Zn(ii)—the first example of a transition metal-coordinated [B12(OH)12]2− compound.

This work demonstrates the first successful electrochemical cycling of a redox-active boron cluster-based material in the solid state. Specifically, we designed and synthesized an ether-functionalized dodecaborate cluster, B12(OCH3)12, which is the smallest redox-active building block in the B12(OR)12 family. This species can reversibly access four oxidation states in solution, ranging from a dianion to a radical cation. We show that a chemically isolated and characterized neutral [B12(OCH3)12]0 cluster can be utilized as a cathode active material in a PEO-based rechargeable all-solid-state cell with a lithium metal anode. The cell exhibits an impressive active material utilization close to 95% at C/20 rate, a high Coulombic efficiency of 96%, and excellent reversibility, with only 4% capacity fade after 16 days of cycling. This work represents a conceptual departure in the development of redox-active components for electrochemical storage and serves as an entry point to a broader class of borane-based materials.

The new class of AV3Sb5 (A=K, Rb, Cs) kagome metals host unconventional charge density wave states seemingly intertwined with their low temperature superconducting phases. The nature of the coupling between these two states and the potential presence of nearby, competing charge instabilities however remain open questions. This phenomenology is strikingly highlighted by the formation of two ''domes” in the superconducting transition temperature upon hole-doping CsV3Sb5. Here we track the evolution of charge correlations upon the suppression of long-range charge density wave order in the first dome and into the second of the hole-doped kagome superconductor CsV3Sb5-xSnx. Initially, hole-doping drives interlayer charge correlations to become short-ranged with their periodicity diminished along the interlayer direction. Beyond the peak of the first superconducting dome, the parent charge density wave state vanishes and incommensurate, quasi-1D charge correlations are stabilized in its place. These competing, unidirectional charge correlations demonstrate an inherent electronic rotational symmetry breaking in CsV3Sb5, and reveal a complex landscape of charge correlations within its electronic phase diagram. Our data suggest an inherent 2kf charge instability and competing charge orders in the AV3Sb5 class of kagome superconductors.

Many of the promising, high-performing solid electrolytes for lithium-ion batteries are amorphous or contain an amorphous component, particularly in the Li thiophosphate Li2S-P2S5 (LPS) compositional series. An explicit study of the local structure in four samples of ostensibly identically prepared 70Li2S-30P2S5 glass reveals substantial variation in the ratio between the two main local structural units in this system: PS43- tetrahedra and P2S74- corner-sharing tetrahedral pairs. Local structural and compositional probes including Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray pair distribution function analysis are employed here to arrive at a consistent description of the relative amounts of isolated tetrahedral units, which vary by 13% across the samples measured. This local structure variation translates to differences in the activation energies measured by electrochemical impedance spectroscopy in these samples, such that the higher concentration of isolated tetrahedra corresponds to a lower activation energy. The measured temperature-dependent ionic conductivity data are compared to conductivity results across the literature reported on the same compositions, highlighting the variation in the measured activation energy for nominally identical samples. These findings have implications for the critical need to play close attention to the local structure in solid electrolytes, particularly in systems that are glasses or glass ceramics, or those that comprise any amorphous contribution.

Author(s): Saber, Muna; Preefer, Molleigh B; Kolli, Sanjeev K; Zhang, William; Laurita, Geneva; Dunn, Bruce; Seshadri, Ram; Van der Ven, Anton

Author(s): Rawlings, Dakota; Lee, Dongwook; Kim, Jeongmin; MagdAƒu, Ioan-Bogdan; Pace, Gordon; Richardson, Peter M; Thomas, Elayne M; Danielsen, Scott P. O; Tolbert, Sarah H; Miller, Thomas F; Seshadri, Ram; Segalman, Rachel A

Successful strategies for the design of crystalline materials with useful function are frequently based on the systematic tuning of chemical composition within a given structural family. Perovskites with the formula ABX3, perhaps the best-known example of such a family, have a vast range of elements on A, B, and X sites, which are associated with a similarly vast range of functionality. Layered double perovskites (LDPs), a subset of this family, are obtained by suitable slicing and restacking of the perovskite structure, with the additional design feature of ordered cations and/or anions. In addition to inorganic LDPs, we also discuss hybrid (organic-inorganic) LDPs here, where the A-site cation is a protonated organic amine. Several examples of inorganic LDPs are presented with a discussion of their ferroic, magnetic, and optical properties. The emerging area of hybrid LDPs is particularly rich and is leading to exciting discoveries of new compounds with unique structures and fascinating optoelectronic properties. We provide context for what is important to consider when designing new materials and conclude with a discussion of future opportunities in the broad LDP area.

The emergence of Alpha, Beta, Gamma, Delta, and Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for several million deaths up to now. Because of the huge amount of vaccine escape mutations in the spike (S) protein for different variants, the design of material for combating SARS-CoV-2 is very important for our society. Herein, we report on the design of a human angiotensin converting enzyme 2 (ACE2) peptide-conjugated plasmonic-magnetic heterostructure, which has the capability for magnetic separation, identification via surface enhanced Raman spectroscopy (SERS), and inhibition of different variant SARS-CoV-2 infections. In this work, plasmonic-magnetic heterostructures were developed using the initial synthesis of polyethylenimine (PEI)-coated Fe

Author(s): Vincent, Rebecca C; Shen, Jimmy-Xuan; Preefer, Molleigh B; Lin, Justin; Seeler, Fabian; Schierle-Arndt, Kerstin; Persson, Kristin A; Seshadri, Ram

The properties of crystalline materials tend to be strongly correlated with their structures, and the prediction of crystal structure from only the composition is a coveted goal in the field of inorganic materials. However, even for the simplest compositions, such prediction relies on a complex network of interactions, including atomic or ionic radii, ionicity, electronegativity, position in the periodic table, and magnetism, to name only a few important parameters. We focus here on the AB2X6 (AB2O6 and AB2F6) composition space with the specific goal of finding new oxide compounds in the trirutile family, which is known for unusual one-dimensional (1D) antiferromagnetic behavior. Through machine learning methods, we develop an understanding of how geometric and bonding constraints determine the crystallization of compounds in the trirutile structure as opposed to other ternary structures in this space. In combination with density functional theory (DFT) calculations, we predict 16 previously unreported candidate trirutile oxides. We successfully prepare one of these and show it forms in the disordered rutile structure, under the preparation conditions adopted here.

Following on the heels of the remarkable lead halide perovskite optoelectronic materials, interest in lead-free halide perovskites has grown rapidly in the past decade. Double perovskite halides with the general formula A₂MᴵMᴵᴵᴵX₆ (where A is a large monovalent cation in the perovskite A site, Mᴵ is a univalent metal, Mᴵᴵᴵ is a trivalent metal, and X is a halide) represent one of the promising classes of such materials, and of these, the iodides are particularly interesting since their band gaps are expected to be similar to those found in the iconic lead-containing phases, APbI₃. However, the successful synthesis of A₂MᴵMᴵᴵᴵI₆ iodides appears to have been elusive. In this work, we examine the likelihood that double perovskite halides will form using a combination of the Goldschmidt tolerance factor and the radius ratio of the trivalent metals, Mᴵᴵᴵ, and rationalize the rarity of double perovskite iodides in terms of these descriptors. Using this model as the formability criterion, we predict the possible existence of more than 300 hitherto unknown double perovskite iodides with organic and inorganic cations in the A site.

Functional materials impact every area of our lives ranging from electronic and computing devices to transportation and health. In this Perspective, we examine the relationship between synthetic discoveries and the scientific breakthroughs that they have enabled. By tracing the development of some important examples, we explore how and why the materials were initially synthesized and how their utility was subsequently recognised. Three common pathways to materials breakthroughs are identified. In a small number of cases, such as the aluminosilicate zeolite catalyst ZSM-5, an important advance is made by using design principles based upon earlier work. There are also rare cases of breakthroughs that are serendipitous, such as the buckyball and Teflon(R). Most commonly, however, the breakthrough repurposes a compound that is already known and was often made out of curiosity or for a different application. Typically, the synthetic discovery precedes the discovery of functionality by many decades; key examples include conducting polymers, topological insulators and electrodes for lithium-ion batteries., Comment: 15 pages, two figures

Author(s): Schauser, Nicole S; Nikolaev, Andrei; Richardson, Peter M; Xie, Shuyi; Johnson, Keith; Susca, Ethan M; Wang, Hengbin; Seshadri, Ram; ClA©ment, RaphaA«le J.; Read de Alaniz, Javier; Segalman, Rachel A

The realization of spin liquid states born from the near-critical regime of the triangular lattice Hubbard model in inorganic materials remains a long-standing challenge, where weak spin-orbit coupling and other small perturbations often induce conventional spin freezing or order. Strong enough spin-orbit coupling, however, can renormalize the electronic wave function and induced anisotropic exchange interactions that promote magnetic frustration. Through the cooperative interplay of spin-orbit coupling and correlation effects, here we show that the triangular lattice magnet NaRuO2 hosts an inherently fluctuating magnetic ground state with thermodynamic properties suggestive of a crossover between dynamic ground states. Despite the presence of a charge gap, we find that low-temperature spin excitations generate a metal-like term in the specific heat and continuum excitations in neutron scattering, reminiscent of spin liquid states found in triangular lattice organic magnets. Further cooling reveals that these fluctuations crossover into a state whose dynamic spin autocorrelation function reflects persistent fluctuations within a highly disordered spin state. These findings instantiate NaRuO2 as a unique, Heisenberg-Kitaev cousin to organic, Heisenberg spin liquid compounds with a low-temperature crossover in quantum disorder driven via the interplay between geometric frustration, extended hopping, and relativistic spin-orbit coupling.

Hybrid layered double perovskite (HLDP) halides comprise hexacoordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and organic amine cations between the layers. Progress on such materials has hitherto been limited to compounds containing main group 3+ ions isoelectronic with Pb

Mechanical strain can modify the structural and electronic properties of methylammonium lead iodide MAPbI3. The consequences of ferroelastic hysteresis, which involves the retention of structural memory upon cycles of deformation, in polycrystalline thin films of MAPbI3 are reported. Repeatedly bent films of MAPbI3 on flexible polyimide substrates were examined using Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) to quantitatively characterize the strain state, populations, and minimum sizes of twin domains. Approximate locations for the coercive stress and saturation on the ferroelastic stress-strain curve are identified, and domains from differently-strained twin sets in the films are found to interact with each other. The presence of specific twin domains is found to correlate to reports of the heterogeneity of strain states with defect content. Long-term stability testing reveals that domain walls are highly immobile over extended periods. Nucleation of new domain walls occurs for specific mechanical strains and correlates closely with degradation of the films. These results help to explain the behavior of ion migration, degradation rate, and photoluminescence in thin films under compressive and tensile strain., 19 pages + References, 9 figures, Supporting Information included

The Wadsley–Roth phase (W0.2V0.8)3O7, crystallizing in a structure obtained through crystallographic shear of 3 × 3 × ∞ ReO3 blocks, is a somewhat rare exemplar for this class of compounds in that ...

A Li-rich polyanionic compound based on V3+ with a previously unknown structure, Li5VF4(SO4)2, has been developed as a high-voltage cathode material for Li-ion batteries. The solvothermal preparati...

Hybrid materials are increasingly demonstrating their utility across several optical, electrical, and magnetic applications. Cu(I) halide-based hybrids have attracted attention due to their strong luminescence in the absence of rare-earths. Here, we report three Cu(I) and Ag(I) hybrid iodides with 1,5-naphthyridine and additional triphenylphosphine (Ph

Raman spectroscopy has capability for fingerprint molecular identification with high sensitivity if weak Raman scattering signal can be enhanced by several orders of magnitudes. Herein, we report a heterostructure-based surface-enhanced Raman spectroscopy (SERS) platform using 2D graphene oxide (GO) and 0D plasmonic gold nanostar (GNS), with capability of Raman enhancement factor (EF) in the range of ∼1010 via light–matter and matter–matter interactions. The current manuscript reveals huge Raman enhancement for heterostructure materials occurring via both electromagnetic enhancement mechanism though plasmonic GNS nanoparticle (EF ∼107) and chemical enhancement mechanism through 2D-GO material (EF ∼102). Finite-difference time-domain (FDTD) simulation data and experimental investigation indicate that GNS allows light to be concentrated into nanoscale “hotspots” formed on the heterostructure surface, which significantly enhanced Raman efficiency via a plasmon–exciton light coupling process. Notably, we have shown that mixed-dimensional heterostructure-based SERS can be used for tracking of cancer-derived exosomes from triple-negative breast cancer and HER2(+) breast cancer with a limit of detection (LOD) of 3.8 × 102 exosomes/mL for TNBC-derived exosomes and 4.4 × 102 exosomes/mL for HER2(+) breast cancer-derived exosomes.

PNb9O25, a Wadsley–Roth compound whose structure is obtained by appropriate crystallographic shear of the ReO3 structure, is a high-power electrode material that can reach 85% of the equilibrium ca...