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Two isoreticular lanthanide metal–organic frameworks (Ln-MOFs), {[Ln2(H2O)6(H2dobdc)6·12H2O}n (Ln = Tb3+ and Gd3+); H4dobdc = 2,5-di-hydroxy-benzene-1,4-di-carboxylic acid), constructed from a hydroxy-functionalized dicarboxybenzene were synthesized and structurally characterized. Single-crystal X-ray crystallography reveals that the two Ln-MOFs were constructed from Ln3+ dimers as secondary building units, which were linked by H2dobdc2− ligands to form three-dimensional (3D) frameworks featuring pcu topology. Interestingly, 1D triangular porous channels were formed in the frameworks with a high density of coordinated and guest water molecules and hydroxy-containing inwall, which provide a hydrophilic and highly oxygenated environment. Magnetic studies indicated the Tb(III) analogue exhibited slow relaxation of magnetization under an applied static field of 2 kOe while the Gd(III) MOF displayed the magnetocaloric effect (MCE) with a magnetic entropy change of 19.5 J kg−1 K−1. At 55 °C under 98% RH, impedance spectroscopy indicated that the Ln-MOFs exhibit high proton conductivities up to 1.63 × 10−2 and 2.51 × 10−2 S cm−1 through the vehicle mechanism, suggesting that the two are highly proton-conducting Ln-MOFs. This work not only demonstrates two rare magnetic-electrical bifunctional Ln-MOFs with high proton-conduction and interesting magnetic properties but also provides potential design guidelines for high-performance Ln-MOF based proton conductors. [ABSTRACT FROM AUTHOR]

A dysprosium(III) metal–organic framework constructed using dysprosium(III) cubanes as secondary building units has been reported to exhibit field-induced slow magnetic relaxation behavior and an unprecedented ecu topology, which is the first example of an 8-connected Ln-cubane-based framework material and a rare Dy4-MOF showing slow magnetic relaxation. [ABSTRACT FROM AUTHOR]

Band structure characteristics, such as band gap and band dispersion, are fundamental properties of materials. Temperature can affect them because of lattice expansion and phonon-induced atomic vibrations. Here, we apply the recently developed electron–phonon renormalization method to study the temperature effect on the band structures of thermoelectric (TE) filled skutterudites BaCo4Sb12, BaFe4Sb12, and YbFe4Sb12 from first-principles. The results reveal that the band gap in BaCo4Sb12 drops slower with temperature compared with our previous study on CoSb3, where it considerably reduces from 0 K to 800 K for BaFe4Sb12 (∼0.222 eV) and YbFe4Sb12 (∼0.201 eV). Furthermore, the band dispersions near the band edges at the Γ-point in the three systems at high temperatures are similar to those at 0 K, and the electron energies have small linewidths, whereas the linewidths for energies near the Fermi level are large. The different phenomena are due to the different phonon vibration-induced electronic structure disorders, reflecting the strength of electron–phonon coupling. Band renormalization would further affect the TE properties of these filled skutterudites. Our work provides a deeper understanding of the temperature-dependent band structure in skutterudites. [ABSTRACT FROM AUTHOR]

Rare earth-based half-Heusler compounds are potential thermoelectric materials with inherently low thermal conductivity. Here, LuNiSb-based compounds were successfully prepared and their electrical and thermal transport properties were simultaneously improved via aliovalent doping of Sn and Co. In addition to optimizing the carrier concentration, a huge suppression of lattice thermal conductivity κL (∼40% at 300 K) was observed, despite the atomic mass and radius of Sn and Co having only small differences compared with those of the substituted matrix atoms. With the help of first-principles calculations, it is discovered that the suppression of κL mainly originates from the deceleration of optical phonons and the enhancement of phonon–phonon (p–p) scattering phase space. Compared with Co-doped LuNiSb-based compounds, Sn-doped ones exhibit better electrical performance, which is probably because of the weaker perturbation of the valence band. Finally, a peak zT of about 0.4 was obtained at 775 K for LuNiSb0.92Sn0.08. This work highlights the simultaneous optimization of electrical and thermal transport properties only by aliovalent doping, which helps develop high-performance thermoelectrics. [ABSTRACT FROM AUTHOR]

Gallium (Ga) is a low melting point metal in the liquid state in the biological environment which presents a unique combination of fluidity, softness, and metallic electrical and thermal properties. In this work, liquid Ga is proposed as a biocompatible electrode material for cell culture by electro-stimulation since the cytotoxicity of Ga is generally considered low and some Ga compounds have been reported to exhibit anti-bacterial and anti-inflammatory activities. Complementarily, polydopamine (PDA) was coated on liquid Ga to increase the attachment capability of cells on the liquid Ga electrode and provide enhanced biocompatibility. The liquid Ga layer could be readily painted at room temperature on a solid inert substrate, followed by the formation of a nanoscale PDA coating layer resulting in a conformable and biocompatible composite electrode. The PDA layer was shown to coordinate with Ga3+, which is sourced from liquid Ga, providing electrical conductivity in the cell culture medium. The PDA–Ga3+ composite acted as a conductive substrate for advanced electro-stimulation for cell culture methods of representative animal fibroblasts. The cell proliferation was observed to increase by ∼143% as compared to a standard glass coverslip at a low potential of 0.1 V of direct coupling stimulation. This novel PDA–Ga3+ composite has potential applications in cell culture and regenerative medicine. [ABSTRACT FROM AUTHOR]

Half-Heusler (HH) alloys have been extensively studied as ternary systems with various intriguing physical properties since their discovery around a century ago. Particularly, HH semiconductors show promising potential as high-temperature thermoelectric materials due to their excellent electrical properties, while their high thermal conductivities restrict their further development and application. In this work, alloyed triple HH (THH) alloys Ti(Fe0.5+xCo0.25Cu0.25−x)Sb (x = 0, 0.025, 0.05, 0.075) with intrinsically low lattice thermal conductivities have been successfully designed and synthesized based on a valence balanced strategy. All the samples are homogeneous single phase, crystalizing in the cubic MgAgAs-type structure with the space group F4¯3m. Fe/Co/Cu distributes randomly on the 4c site, leading to greatly enhanced point-defect phonon scattering and thus significantly lower lattice thermal conductivity than conventional 18-electron HHs and double HH TiFe0.5Ni0.5Sb. Meanwhile, the electrical transport properties can be feasibly optimized by partial substitution of Cu with Fe. As a result, a peak zT value of 0.71 has been realized for the sample with x = 0.025 in the temperature range of 900 to 1024 K, demonstrating the potential of alloyed THH compounds as high-performance thermoelectric materials. [ABSTRACT FROM AUTHOR]

Understanding the micro-mechanism of the temperature dependence of the band gap in all-inorganic perovskites is of great significance for their optoelectronic and photovoltaic applications in various temperature environments. Herein, based on the recently developed electron-phonon renormalization method, the temperature-dependent band gaps of the optoelectronic perovskite CsPbI3 are studied from 300 K to 750 K (including orthorhombic, tetragonal, and cubic phases). It is found that the temperature-induced structural fluctuation makes the structure of perovskites deviate from the 0 K one, and the corresponding renormalized band gap differs from that at 0 K, especially for the high-temperature cubic phase (e.g., ΔEg is ∼177 meV at 600 K). However, within the temperature range of each CsPbI3 phase, the band gap Eg is enlarged slightly with the increase of temperature (e.g., ΔEg is ∼26 meV from 600 K to 750 K for the cubic phase), showing the insensitivity of the structural fluctuation effect to the temperature change. The reason is that the chemical characters of band edges are determined by PbI3−, and due to the strong correlation between Pb and I, the Pb–I bond lengths and Pb–I–Pb bond angles are almost unchanged as the temperature increases. Our work provides a fundamental understanding of the temperature-dependent band gaps in all-inorganic perovskites and shed light on the commercialization of perovskites. [ABSTRACT FROM AUTHOR]

Electron–phonon interaction (EPI) has been widely suited in electrical transport properties. Nevertheless, its critical impact on the lattice thermal transport has been revealed in the last few years. Recently, people found that EPI can remarkably reduce the lattice thermal conductivity under a high carrier concentration and low temperature such as in silicon and two-dimensional materials; however, the discussions on thermoelectric (TE) materials are few. In this study, we investigate the EPI effect on the lattice thermal conductivities of skutterudites CoSb3 and p-type filled BaFe4Sb12. At 300 K with 1021 cm−3 carrier concentration, the lattice thermal conductivity of CoSb3 decreases from 10.7 W m−1 K−1 to 7.03 W m−1 K−1 (hole doping, reduction 34.3%) and 8.18 W m−1 K−1 (electron doping, reduction 23.6%), respectively, while that of BaFe4Sb12 decreases from 3.24 W m−1 K−1 to 1.14 W m−1 K−1 (5 × 1021 cm−3 for hole concentration) with a reduction of 64.8%. The significant EPI effect in BaFe4Sb12 is mainly due to the large density of states (DOS) and strong EPI strength. Our study reveals that EPI plays an important role in the lattice thermal conductivity of filled skutterudites, and it can further optimize their TE performances. [ABSTRACT FROM AUTHOR]

Precise control of the structures and magnetic properties of a molecular material constitutes an important challenge to realize tailor-made magnetic function. Herein, we report that the ligand-directed coordination self-assembly of a dianionic cobalt(II) mononuclear complex and selective organic linkers has led to two distinct dicobalt(II) complexes, [Co2(pdms)2(bpym)3]·2MeCN (1) and [Co(pdms)(bipm)]2·3DMF (2) (H2pdms = 1,2-bis(methanesulfonamide)benzene; bpym = 2,2′-bipyrimidine; bimp = 1,4-bis[(1H-imidazol-1-yl)methyl]benzene). Structural analyses revealed that complexes 1 and 2 are discrete binuclear molecules containing two neutral {Co(pdms)} species bridged by bpym and bimp ligands, respectively, forming an exchange-coupled Co II2 dimer and a rare Co II2 metallocycle. Magnetic studies found that 1 exhibits considerable antiferromagnetic interactions transferred by the bpym bridge while negligible magnetic interactions in 2 due to the long bimp ligands. Interestingly, both the complexes show significant magnetic anisotropy and thus exhibit slow magnetic relaxation under an external dc field originating from spin–lattice relaxation. Detailed theoretical calculations were further applied to understand the magnetic interactions and magnetic anisotropy in 1 and 2. The foregoing results highlight that coordination solids with programmed structures and magnetic properties can be designed and prepared through a judicious selection of molecular complex building blocks and organic linkers. [ABSTRACT FROM AUTHOR]

Establishing the relationships between chemical bonding and functional properties is at the core of condensed matter and materials science and is key to the rational design of novel materials. High-throughput (HTP) studies provide an opportunity to explore large sets of materials thereby enabling a global view of relationships between bonding and properties. Here we use HTP methods to investigate ABO3 cubic perovskites for n-type thermoelectric properties. Of the 313 ABO3 entries investigated, 46 are found to have a finite band gap and meet the lattice stability criterion. Four distinctly different structures of conduction band minima (CBMs) are identified. These are based on classification by the band degeneracy and location of the band edge. These four types of CBMs arise from four different types of chemical bonding; compounds with triply degenerate CBMs from B-site t2g orbitals have both the largest density of states near the CBM and the most favorable Pisarenko curves. They also possess the best electrical transport properties including consideration of the relaxation times from the deformation potential approximation. When the calculated electrical transport properties are combined with the lattice thermal conductivity, 13 ABO3 perovskites with high ZT (ZT > 0.5) values at 700 K are identified as n-type candidates. This work demonstrates the importance of chemical bonding in determining transport properties. [ABSTRACT FROM AUTHOR]

Liquid metals, highly conductive and flowable metals, are increasingly becoming versatile choices for soft electronics and wearable devices. High resolution liquid metal patterning strategies accommodative to different substrate materials and geometries are highly desirable. Here, the intermetallic wetting effect between an oxide-free eutectic gallium indium (EGaIn) alloy and a high-surface-energy gold (Au) precursory layer is utilised to fabricate EGaIn patterns with resolutions up to 1.3 μm. The feasibility, reliability, and precision of the method for patterning EGaIn on planar, non-planar, rigid, and flexible substrates of different materials are highlighted. The liquid metal patterns are found to self-adapt to well-defined, curved cross-sectional profiles and their electrical conducting behaviours correlate well with their geometrical dimensions. The EGaIn tracks on flexible polydimethylsiloxane (PDMS) and Ecoflex substrates show reversible resistance changes during repeated strain test, revealing excellent stability under mechanical deformations. A fully functional 3D liquid metal circuit and a resistive motion sensor are designed to demonstrate the potentials of the method for fabricating 3D electronic devices and flexible sensors. [ABSTRACT FROM AUTHOR]

Precise modulation of the structure and magnetic properties of coordination compounds is of great importance in the development of framework magnetic materials. Herein, we report that the coordination self-assembly of a neutral cobalt(II) magnetic building block and selective pyridine derivatives as organic linkers has led to two distinct cobalt(II) coordination polymers, {Co(DClQ)2(bpy)}n (1) and {Co2(DClQ)4(tpb)}n (2) (DClQ = (5,7-dichloro-8-hydroxyquinoline; bpy = 4, 4′-dipyridine; tpb = 1,2,4,5-tetra(4-pyridyl)benzene)). Structural analyses revealed that 1 and 2 are one-dimensional (1D) and 2D coordination polymers containing the same neutral magnetic building block [Co(DClQ)2] bridged by bitopic bpy and tetratopic tpb ligands, respectively. Both the complexes have a distorted octahedral CoN4O2 coordination geometry around each cobalt center offered by the bidentate ligand and organic linkers. Magnetic studies reveal large easy-plane and easy-axis magnetic anisotropy for 1 and 2, respectively. However, because of the weak antiferromagnetic coupling between the bpy-bridged CoII centers, no slow relaxation of the magnetization was observed in 1 under both zero or applied dc fields. Interestingly, complex 2 exhibits slow magnetic relaxation under external fields, indicative of a framework single-ion magnet of 2. Theoretical calculations further support the experimental results and unveil that the D values are +65.3 and −91.2 cm−1 for 1 and 2, respectively, while the magnetic exchange interaction was precisely estimated as −0.16 (1) and −0.009 (2) cm−1. The foregoing results show that the structural dimensionality and magnetic properties can be rationally modified via pre-designed magnetic building blocks and a suitable choice of organic bridging ligands. [ABSTRACT FROM AUTHOR]

Two cyanide-bridged V-shaped isostructural trinuclear complexes [{(Tp*)FeIII(CN)3}2MII(bztpen)]·Sol (M = Fe, Sol = CH3OH·3H2O, 1; M = Co, Sol = 2CH3OH·2H2O, 2; bztpen = N-benzyl-N,N′,N′-tris(2-methylpyridyl)ethylenediamine; Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) were synthesized and characterized. The bztpen ligand serves as a tetradentate capping ligand around the inner metal ion, leaving one pyridyl group intact. Complex 1 exhibits a spin crossover (SCO) behavior between the {Fe IIILS Fe IIHS Fe IIILS } and {Fe IIILS Fe IILS Fe IIILS } spin isomers, while 2 shows both thermally- and photo-induced electron-transfer coupled spin transition (ETCST) property between the {Fe IIILS Co IIHS Fe IIILS } and {Fe IIILS Co IIILS Fe IILS } valence isomers. The total entropy changes for 1 and 2 between their corresponding two electronic states were found to be very close with the values of 87.46 and 84.49 J mol−1 K−1, respectively, indicating the comparable thermal energy barriers necessary for either an SCO or ETCST event for such a given system. Furthermore, both complexes undergo desolvation-induced irreversible and sharp magnetic change at high temperatures. [ABSTRACT FROM AUTHOR]

Revealing the intrinsic defects and further understanding the corresponding origin are of crucial importance in optimizing and designing novel thermoelectric materials. In this work, we applied the first-principles studies on the defects of classical thermoelectric materials XTe (X = Ge, Sn, and Pb). Our results show that the X-vacancy defects in GeTe (in both rhombohedral and cubic phases) and cubic SnTe usually possess low formation energies, leading to the strong tendency of p-type electrical transport. Meanwhile, the formation energies of the defects in PbTe with relatively high stability, such as VTe, TePb, etc., depend sensitively on the chemical potentials of Pb, as well as the accuracy of the band gap, and those defects tend to induce weak n-type transport by default. The intrinsic defect types and the induced carrier concentrations are qualitatively in agreement with the reported data. Detailed analyses reveal that the formation energies of the intrinsic defects depend strongly on the energy positions of valence band maxima (VBM), where compounds with high VBM favor acceptor defects. PbTe shows the lowest VBM among the four materials, due to the low energy of the 6s2 lone-pair electrons, which fundamentally causes the distinctly different intrinsic defects. [ABSTRACT FROM AUTHOR]

One of the major challenges in the development of soft electronics is to devise scalable and automated strategies for the microfabrication of deformable and flexible electronic components and sensors. Liquid metals have demonstrated unique characteristics suitable for such applications. To date, conductive patterning using liquid metals has mainly focused on writing or injection of liquid metals into prefabricated channels, requiring multiple complicated procedures and reliance on specific inks formulae. Here a new strategy has been introduced for direct patterning of liquid metal particles onto substrates via UV photolithography. A variety of different tracks, patterns and sensors, on both rigid and flexible substrates, are demonstrated using a dispersion of eutectic alloy of gallium and indium in photoresist, to present the extent of capability of the introduced method. The method provides simple, effective, high-resolution and precision patterning of liquid metals for the emerging fields of soft electronics and sensors. [ABSTRACT FROM AUTHOR]

Two azido-bridged homospin Fe(II)/Co(II) coordination polymers [Fe2(Bzp)2(N3)4]n (1) and [Co4(Bzp)4(N3)8·(MeOH)2]n (2) (bzp = 2-benzoylpyridine) are prepared, which consist of one-dimensional neutral chains with pure EO-azido (μ2-1,1-N3) bridges. Magnetically, both 1 and 2 exhibit considerable intrachain ferromagnetic interactions which benefit from the EO-azido bridging mode, leading to typical single-chain magnet (SCM) behavior under both the "infinite-size" and "finite-size" regime and pronounced hysteresis loops. As far as the bridging network is concerned, complex 1 represents not only a rare example of homospin Fe(II)-based SCMs but also the first Fe(II) chain compound with pure EO-azido bridges. [ABSTRACT FROM AUTHOR]

Dynamic precipitation phenomena are usually observed in Cu- and Ag-based thermoelectric compounds undergoing a temperature rise, affecting the stability and thermoelectric figure of merit zT. The present work demonstrates that rational controlling of the Cu content would eliminate unstable factors in BaCu2Te2, beneficial for achieving stable and reliable thermoelectric materials. Over-stoichiometric Cu in BaCu2Te2 can not only optimize the hole concentration approaching the optimal one, but also lead to the stable degenerate semiconducting behaviors. More importantly, despite the intrinsically low lattice thermal conductivity originating from the small phonon group velocities and mean free path, the excess Cu content generates widely distributed Cu-rich nano-precipitates with a size of 20–50 nm. These nano-precipitates significantly contribute to low-frequency phonon scattering for further reducing the thermal conductivity, and thus more than 25% of the κ reduction has been achieved at room temperature (0.95 W m−1 K−1 for BaCu2Te2 and 0.70 W m−1 K−1 for BaCu2.08Te2). A high figure of merit zT = 1.31 at 833 K has been realized for the sample BaCu2+xTe2 (x = 0.04), which is superior to the state of the art p-type Zintl phase thermoelectric materials. [ABSTRACT FROM AUTHOR]

Liquid metal interfaces with their unique chemistry can provide an extraordinary tool to synthesise materials with controlled characteristics at room temperature. Here, the templated synthesis of cupric oxide (CuO) onto a gallium based liquid metal (galinstan) surface is explored. The interaction between galinstan and copper sulphate solution yields initial interfacial CuO sheets and then secondary dendritic nanostructures are grown from the sheets. It is shown that the pH of the aqueous environment plays a critical role in tuning the synthesis of substoichiometric CuxO to CuO. For enhancing the interfacial area and establishing heterojunctions, the liquid metal is processed into a suspension of micro and nano droplets by sonication and the example of using the synthesised nano structures for enhanced photocatalysis is demonstrated for the catalysis of a model dye. This study presents a facile approach for synthesising highly functional systems based on liquid metals, and it can be extended to explore other metal oxide–liquid metal composites. [ABSTRACT FROM AUTHOR]

Herein we study the effect alloying Yb onto the octahedral cite of Te doped Mg3Sb1.5Bi0.5 has on transport and the material's high temperature stability. We show that the reduction in mobility can be well explained with an alloy scattering argument due to disrupting the Mgoctahedral–Mgtetrahedral interaction that is important for placing the conduction band minimum at a location with high valley degeneracy. We note this interaction likely dominates the conducting states across n-type Mg3Sb2–Mg3Bi2 solid solutions and explains why alloying on the anion site with Bi isn't detrimental to Mg3Sb2's mobility. In addition to disrupting this Mg–Mg interaction, we find that alloying Yb into the Mg3Sb2 structure reduces its n-type dopability, likely originating from a change in the octahedral site's vacancy formation energy. We conclude showing that while the material's figure of merit is reduced with the addition of Yb alloying, its high temperature stability is greatly improved. This study demonstrates a site-specific alloying effect that will be important in other complex thermoelectric semiconductors such as Zintl phases. [ABSTRACT FROM AUTHOR]

Lithium metal batteries are a promising candidate for future high-energy-density energy storage. However, dendrite growth and the high reactivity of the Li metal anode result in low cycling efficiency and severe safety concerns. Here, we present a strategy to stabilize the lithium metal anode through cation doping in Li7La3Zr2O12 (LLZOM, M = dopant). High-throughput automated reaction screening together with a machine learning approach are developed to evaluate possible reactions and the thermodynamic stability of the Li‖LLZOM interfaces under various chemical conditions. It is discovered that some dopants, such as M = Sc3+ (doping on Zr site), Ce3+ (La or Zr), Ac3+ (La), Y3+ (La or Zr), Tm3+ (La or Zr), Er3+ (La or Zr), Ho3+ (La or Zr), Dy3+ (La or Zr), Nd3+ (La or Zr), Tb3+ (La or Zr), Pr3+ (La), Pm3+ (La or Zr), Sm3+ (La or Zr), Gd3+ (La or Zr), Lu3+ (La), Ce4+ (Zr), Th4+ (Zr), and Pa5+ (Zr), exhibit thermodynamic stability against Li; while others, M = Ca2+ (La or Zr), Yb3+ (La), Br3+ (Li), Te4+ (Zr), Se4+ (Zr), S4+ (Zr), Hf4+ (Zr), Cl5+ (Zr), and I5+ (Zr), may lead to the spontaneous formation of a stable, passivating solid electrolyte interphase (SEI) layer on the Li metal, and alleviate dendritic lithium growth. From the machine learning approach, the formation energy of oxides MxOy emerges as the most crucial feature dominating the route of interface reactions, implying that the M–O bond strength governs the interface stability of the cation-doped LLZOM. The machine learning model then predicts 18 unexplored LLZOM systems, which are all validated in subsequent calculations. Our work offers practical insights for experimentalists into the selection of appropriate dopants in LLZO to stabilize Li metal anodes in solid-state batteries. [ABSTRACT FROM AUTHOR]

Exploring the concept of liquid processing and solidification of low melting point alloys can provide new routes for the creation of functional micro and nanoparticles. Here we show that it is possible to produce particles of Field's metal (an alloy of bismuth 32.5 wt%, tin 16.5 wt% and indium 51 wt%) in a one-step mechanical agitation (ultrasonication) procedure. The synthesis takes place just above 62 °C, the melting point of Field's metal, and results in the formation of low-dimensional particles after solidification. It is demonstrated that the sonication process produces nearly spherical core–shell metal–metal oxide heterostructures. Classic alloy-related defects, in the forms of grain boundaries and edge locations, emerge after the solidification. We show that by the incorporation of Ag, either using direct alloying or an Ag salt precursor during the sonication process, this metal appears in the core of the metal–metal oxide heterostructures. Interestingly, the modification of particles with Ag gives specific selectivity for the degradation of two typical azo dyes. The one-step low-temperature synthesis and solidification procedure, presented in this work, can be readily extended for designing catalysts or other functional materials with desired specificity and selectivity. [ABSTRACT FROM AUTHOR]

Electronegative filling has been revealed to effectively reduce the lattice thermal conductivity and optimize the thermoelectric performance of skutterudites. However, experimental data related to rattling-mode vibrations are still not available. In this work, more S atoms were filled into the voids of CoSb3 along with substitution of Ni at Co-sites to better observe the rattling-mode vibrations due to charge compensation. Rattling-mode vibrations around 54 cm−1 were detected unambiguously by Raman scattering spectroscopy, confirming the origins of the significant dropping of the lattice thermal conductivity. The proposed study validated Raman scattering spectroscopy as a convenient technique for studying rattling-mode vibrations of electronegatively filled skutterudites. The results also showed that the Ni solubility in skutterudites was increased with S filling, which was effective for adjusting and controlling the carrier concentrations. A record-high carrier concentration of 3.99 × 1021 cm−3 was achieved. [ABSTRACT FROM AUTHOR]

Liquid metals can offer extraordinary properties for application in the field of sensors, yet their potential has not been fully realised. In this work, we present a heterostructure mix of eutectic alloy of gallium and two dimensional (2D) flakes of tungsten oxides (WO3) for gas sensing. We show that the eutectic alloy of EGaIn, made of gallium and indium, can be co-sonicated with acid bath synthesised 2D WO3 for chemisorption sensing of H2 gas molecules. We demonstrate that this co-sonication results in extra trap bands within the bandgap of WO3 to enhance the gas sensing properties. Another interesting observation was the effect on reducing the size of the sonicated EGaIn droplets in the presence of 2D WO3 flakes, which is likely due to the increase of shear force during the sonication. Mixes using different ratios of WO3 and EGaIn were synthesised. The optimum gas sensing operation in terms of response factor was seen in the 70% WO3–30% EGaIn mix. This work provides a viable pathway towards a new platform where liquid metals can be used for sensing applications and they offer advantages to augment the capabilities of sensors. [ABSTRACT FROM AUTHOR]

High-symmetry crystal structures are preferred for thermoelectrics because high structural symmetry usually yields good electron transport properties. Entropy engineering is an effective approach to improve the structural symmetry of low-symmetry materials, and thus to enhance their thermoelectric performance. In this study, via introducing Te into the argyrodite-type compound Cu7PSe6, the configurational entropy is significantly increased to successfully improve its initial low-symmetry cubic structure (P213) to the high-symmetry cubic structure (F4̅3m) at room temperature. Such improved structural symmetry leads to a high density-of-state effective mass but similar carrier mobility in the same carrier concentration range as compared with the pristine Cu7PSe6. Thus, significantly optimized electron transport properties are achieved in the Te-alloyed Cu7PSe6 samples. In particular, at room temperature, the power factor of the high-symmetry cubic Cu7PSe5.7Te0.3 sample is about 15-times higher than that of the low-symmetry Cu7PSe6 matrix. Combining the well-maintained ultralow lattice thermal conductivity, a maximum ZT of around 0.55 at 600 K is obtained in Cu7PSe5.7Te0.3. This work strongly shows that entropy engineering using multiple components is a very powerful strategy to discover or design novel high-performance TE materials starting from low-symmetry compounds. [ABSTRACT FROM AUTHOR]

The electrical transport properties of the emerging thermoelectric Cu2Se are exceptionally good; this is unexpected considering the strong disordering or liquid-like structure of the Cu sublattice which normally leads to poor electrical conductivity. Via first principles calculations, however, we find that the structural variations on the Cu sites have minor effects on the band-edge electronic states and electrical transport properties. In particular, the Cu vacancies affect very little the edge states of the valence band for the low-temperature ordered Cu2Se phase, except for shifting the Fermi levels. The feature is also applicable to the high temperature liquid-like phase with copper vacancies and disorder. The calculated Seebeck coefficient and its carrier concentration dependence are consistent with available experiments and confirm the band rigidity. The results imply that the electrical transport is predominantly determined by the face centered cubic Se sublattice in Cu2Se. Although the lattice thermal conductivity is minimized by the disordered Cu sublattice with “Phonon Liquid” behavior, the electron transport is maintained by the ordered Se sublattice, which provides the “Electron Crystal” characteristic. The feature whereby Cu has a minor effect on the electrical transport can also be found in other copper chalcogenides such as Cu2S, also shown in this study. [ABSTRACT FROM AUTHOR]

Recently, liquid-like superionic thermoelectric materials have attracted great attention due to their extremely low lattice thermal conductivity and high thermoelectric figure of merit (ZT). Argyrodite-type compounds are typical superionic semiconductors with two independent structural units that can be used to separately tune electrical and thermal transport properties. In this work, we report that Cu8GeSe6 with an argyrodite structure is a new class of thermoelectric materials with extremely low lattice thermal conductivity. The presence of two independent structural units in Cu8GeSe6 provides the possibility of greatly improving its electrical transport properties while maintaining ultralow lattice thermal conductivity. By alloying Ag and Te in Cu8GeSe6, the ZT values are significantly improved to above unity at 800 K in Cu7.6Ag0.4GeSe5.1Te0.9, comparable with the best superionic liquid-like thermoelectric materials. The ultralow thermal conductivity is mainly attributed to the weak chemical bonding between Cu atoms and the rigid [GeSe6] sublattice. [ABSTRACT FROM AUTHOR]

We prepared in this work an anchoring porphyrin and a series of hat-porphyrins. The zinc atom of the hat-porphyrins can be coordinated axially with the pyridine moiety of the anchoring porphyrin which is anchored on the titania surface by a carboxyl group. The structures of the assemblies were confirmed using computational calculations, transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). Solar cell devices of the monomer anchoring porphyrin and its assemblies were fabricated and the photovoltaic performances were measured under standard AM 1.5 sunlight irradiance. We found that the assembly devices showed higher JSC and lower VOC than that of the monomer anchoring porphyrin device. However, the comprehensive influence of JSC and VOC led to an enhancement in the solar-to-electric power-conversion efficiency (PCE) of the assemblies. We also studied the variation of JSC and VOC using electronic absorption and emission spectroscopy, charge extraction measurements, transient photovoltage decay measurements and electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Alloying, to minimize the energy offset between the two valence bands of PbTe, has been well demonstrated to yield thermoelectric performance enhancements. Distinct from the currently known alloying species such as MnTe, MgTe, CdTe, PbSe and PbS, where the high performance partially comes from the alloy phonon scattering as well as because of the high alloying content of ≥3%, YbTe, even with a concentration as low as 1%, is found here to have an extraordinary role in engineering the band structure to achieve a thermoelectric figure of merit, zT, approaching 1.8, without relying on strong phonon scattering. This work demonstrates new insight into the further improvement of thermoelectric materials, because this strategy leaves the feasibility of lattice thermal conductivity reduction nearly unaffected, which can be obtained by other well-demonstrated approaches such as nanostructuring. [ABSTRACT FROM AUTHOR]

A dysprosium(III) metal-organic framework constructed using dysprosium(III) cubanes as secondary building units has been reported to exhibit field-induced slow magnetic relaxation behavior and an unprecedented ecu topology, which is the first example of an 8-connected Ln-cubane-based framework material and a rare Dy 4 -MOF showing slow magnetic relaxation.

Understanding the micro-mechanism of the temperature dependence of the band gap in all-inorganic perovskites is of great significance for their optoelectronic and photovoltaic applications in various temperature environments. Herein, based on the recently developed electron-phonon renormalization method, the temperature-dependent band gaps of the optoelectronic perovskite CsPbI 3 are studied from 300 K to 750 K (including orthorhombic, tetragonal, and cubic phases). It is found that the temperature-induced structural fluctuation makes the structure of perovskites deviate from the 0 K one, and the corresponding renormalized band gap differs from that at 0 K, especially for the high-temperature cubic phase ( e.g. , Δ E g is ∼177 meV at 600 K). However, within the temperature range of each CsPbI 3 phase, the band gap E g is enlarged slightly with the increase of temperature ( e.g. , Δ E g is ∼26 meV from 600 K to 750 K for the cubic phase), showing the insensitivity of the structural fluctuation effect to the temperature change. The reason is that the chemical characters of band edges are determined by PbI 3 - , and due to the strong correlation between Pb and I, the Pb-I bond lengths and Pb-I-Pb bond angles are almost unchanged as the temperature increases. Our work provides a fundamental understanding of the temperature-dependent band gaps in all-inorganic perovskites and shed light on the commercialization of perovskites.

Precise control of the structures and magnetic properties of a molecular material constitutes an important challenge to realize tailor-made magnetic function. Herein, we report that the ligand-directed coordination self-assembly of a dianionic cobalt(II) mononuclear complex and selective organic linkers has led to two distinct dicobalt(II) complexes, [Co 2 (pdms) 2 (bpym) 3 ]·2MeCN (1) and [Co(pdms)(bipm)] 2 ·3DMF (2) (H 2 pdms = 1,2-bis(methanesulfonamide)benzene; bpym = 2,2'-bipyrimidine; bimp = 1,4-bis[(1 H -imidazol-1-yl)methyl]benzene). Structural analyses revealed that complexes 1 and 2 are discrete binuclear molecules containing two neutral {Co(pdms)} species bridged by bpym and bimp ligands, respectively, forming an exchange-coupled CoII2 dimer and a rare CoII2 metallocycle. Magnetic studies found that 1 exhibits considerable antiferromagnetic interactions transferred by the bpym bridge while negligible magnetic interactions in 2 due to the long bimp ligands. Interestingly, both the complexes show significant magnetic anisotropy and thus exhibit slow magnetic relaxation under an external dc field originating from spin-lattice relaxation. Detailed theoretical calculations were further applied to understand the magnetic interactions and magnetic anisotropy in 1 and 2. The foregoing results highlight that coordination solids with programmed structures and magnetic properties can be designed and prepared through a judicious selection of molecular complex building blocks and organic linkers.

Precise modulation of the structure and magnetic properties of coordination compounds is of great importance in the development of framework magnetic materials. Herein, we report that the coordination self-assembly of a neutral cobalt(II) magnetic building block and selective pyridine derivatives as organic linkers has led to two distinct cobalt(II) coordination polymers, {Co(DClQ) 2 (bpy)} n (1) and {Co 2 (DClQ) 4 (tpb)} n (2) (DClQ = (5,7-dichloro-8-hydroxyquinoline; bpy = 4, 4'-dipyridine; tpb = 1,2,4,5-tetra(4-pyridyl)benzene)). Structural analyses revealed that 1 and 2 are one-dimensional (1D) and 2D coordination polymers containing the same neutral magnetic building block [Co(DClQ) 2 ] bridged by bitopic bpy and tetratopic tpb ligands, respectively. Both the complexes have a distorted octahedral CoN 4 O 2 coordination geometry around each cobalt center offered by the bidentate ligand and organic linkers. Magnetic studies reveal large easy-plane and easy-axis magnetic anisotropy for 1 and 2, respectively. However, because of the weak antiferromagnetic coupling between the bpy-bridged Co II centers, no slow relaxation of the magnetization was observed in 1 under both zero or applied dc fields. Interestingly, complex 2 exhibits slow magnetic relaxation under external fields, indicative of a framework single-ion magnet of 2. Theoretical calculations further support the experimental results and unveil that the D values are +65.3 and -91.2 cm -1 for 1 and 2, respectively, while the magnetic exchange interaction was precisely estimated as -0.16 (1) and -0.009 (2) cm -1 . The foregoing results show that the structural dimensionality and magnetic properties can be rationally modified via pre-designed magnetic building blocks and a suitable choice of organic bridging ligands.

Two cyanide-bridged V-shaped isostructural trinuclear complexes [{(Tp*)FeIII(CN)3}2MII(bztpen)]·Sol (M = Fe, Sol = CH3OH·3H2O, 1; M = Co, Sol = 2CH3OH·2H2O, 2; bztpen = N-benzyl-N,N',N'-tris(2-methylpyridyl)ethylenediamine; Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) were synthesized and characterized. The bztpen ligand serves as a tetradentate capping ligand around the inner metal ion, leaving one pyridyl group intact. Complex 1 exhibits a spin crossover (SCO) behavior between the {FeIIILSFeIIHSFeIIILS} and {FeIIILSFeIILSFeIIILS} spin isomers, while 2 shows both thermally- and photo-induced electron-transfer coupled spin transition (ETCST) property between the {FeIIILSCoIIHSFeIIILS} and {FeIIILSCoIIILSFeIILS} valence isomers. The total entropy changes for 1 and 2 between their corresponding two electronic states were found to be very close with the values of 87.46 and 84.49 J mol-1 K-1, respectively, indicating the comparable thermal energy barriers necessary for either an SCO or ETCST event for such a given system. Furthermore, both complexes undergo desolvation-induced irreversible and sharp magnetic change at high temperatures.

A detailed account of the first total synthesis of alotaketal A, a tricyclic spiroketal sesterterpenoid that potently activates the cAMP signaling pathway, is provided. The synthesis employs both intra- and intermolecular reductive allylation of esters for assembling one of the fragments and their coupling. A Hg(OAc)2-mediated allylic mercuration is used to introduce the C22-hydroxyl group. The subtle influence of substituents over the course of the spiroketalization process is revealed. The synthesis confirms the relative and absolute stereochemistry of (-)-alotaketal A and allows verification of alotaketal A's effect over cAMP signaling using reporter-based FRET imaging assays with HEK 293T cells. Our studies also revealed alotaketal A's unique activity in selectively targeting nuclear PKA signaling in living cells.