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In this study, we report an enormously simple green approach for the synthesis of polyaniline hybrid (PANI-SO) nanofibers in emeraldine salt form. We have carried out the synthesis via an interfacial polymerization method using vegetable oil as an organic phase instead of the commonly used solvents like CHCl3, CCl4, etc. Characterization techniques such as Fourier transform infrared (FTIR), UV–visible, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used for studying the synthesized polyaniline hybrid nanofibers. An interesting observation is the crystallization of small organic molecules in the PANI matrix. PANI-SO shows a pseudocapacitance behavior with a capacitance value of 302 F g–1 at a current density of 1 A g–1. In addition, the material shows an energy density of 26.8 W h kg–1 and a maximum power density of 402.6 W kg–1. Furthermore, the PANI-SO electrode maintains about 84% of the initial capacitance after 1000 cycles. Similarly, the PANI-SO symmetric solid-state supercapacitor shows an areal capacitance of 118.7 mF cm–2 and retains a stability of 80% even after 1000 cycles. Thus, the PANI-SO electrode shows a good cyclic performance, which implies the structural stability of PANI-SO nanofibers. The electrochemical properties of PANI-SO are compared with those of PANI nanofibers synthesized by taking CHCl3 as the organic phase and keeping all other parameters identical. PANI-SO is observed to be a superior material compared to the latter one. All electrochemical analyses show that the PANI synthesized using cooking soyabean oil (PANI-SO) is an effective supercapacitor material.

We present results on growth of ReS2 thin film both on c plane sapphire substrate and MoS2 template by pulsed laser deposition (PLD). Films tend to grow with (0001)ReS2 ⊥ (0001)Al2O3 and (0001)ReS2 ⊥ (0001)MoS2 ∥ (0001)Al2O3 at deposition temperature below 300 °C. Films are polycrystalline grown at temperature above 300 °C. The smoothness and epitaxial quality of the films are significantly improved when grown on MoS2 template compared to sapphire substrate. The results show that PLD is suitable to grow ReS2 thin film over large area (10 × 10 mm2) for practical device application.

Designing non-noble metal based electrocatalysts for efficient overall water splitting (OWS) solves a critical bottleneck of sustainable water electrolyzer technology. Here, we elucidate real-time mechanistic insights into the promotional effect of Ni substitution on the bifunctional OWS activity of N-doped graphite carbon (NGC) supported molybdenum and tungsten carbides (Ni-MoC/WC@NGC). Ni substitution yields multi-fold improvement in water splitting activity over the pristine systems that are comparable to commercial Pt/C for HER and better than IrO2 in case of OER. Ni-MoC@NGC champions in HER activity exhibiting an onset overpotential of 65 mV and current density of 140 mA/cm2 at -370 mV (v RHE) in acidic media. Their excellent OWS activity in alkaline media prompted us to construct a H2O electrolyzer where the bifunctional Ni-MoC@NGC system shows a comparable cell voltage to the PtǁIrO2 pair and could split water aided by a 1.5V AAA commercial battery. First principle calculations and in-situ probing of the local Ni and W sites through quick-XAS during electrochemical processes provide valuable insights into how the adsorption energies of intermediates and reaction kinetics are modulated at different catalytic sites with the promotional electronic effect of Ni substitution.

The structural and magnetic properties of Gd2−xNdxPdSi3 (x = 0, 0.75, 1, 2) have been studied using X-ray diffraction (XRD), exchange bias and magnetization measurements. The end compounds (x = 0, 2) along with the solid solutions of them are found to crystallize in the hexagonal superstructure having space group P6/mmc. The rare-earth (RE) ions are occupying at two different crystallographically inequivalent sites (2b and 6h), which is similar to all ordered members of the RE2PdSi3 series. The absence of chemical phase separation and formation of true solid solutions are confirmed by the XRD analysis. No signature of exchange bias has been observed signifying the absence of coexistence of magnetic phases. The origin of complex magnetic behaviour in Gd2−xNdxPdSi3 is observed due to the separate magnetic ordering and two available crystallographic sites for magnetic ion. The spin-glass behaviour near ferromagnetic transition in Nd2PdSi3 and anomalous bifurcation in zero-field-cooled and field-cooled magnetization curves in Gd2PdSi3 originates from the proximity and overlap of the transition temperatures of the two RE magnetic ions present in two inequivalent sites, and strongly correlated to the interatomic and intra-atomic distances between RE atoms occupying two crystallographic sites.

Electrochemical CO2 reduction (eCO2R) is one of the most promising and effective technologies to reduce CO2 into value-added chemicals and fuels, reducing the dependence on fossil fuels. However, the efficiency and selectivity of eCO2R is dependent on the interactions between the catalyst surface and the intermediates, which is majorly due to the inherent nature of the catalyst and other parameters like mass transport, electrolyte and intermediate coverage on the surface. There exists a parity between the existing experimental and theoretical catalyst design strategies. In this review we intend to discuss the rational design of catalysts based on transition metals to achieve highly efficient eCO2R. The strategies focused on here include the ligand effect, alloying, strain engineering, heterostructure formation, oxide derivation and the use of transition-metal chalcogenides, phosphides, nitrides and carbides. These strategies are effective in modulating the electronic structure, adsorption geometries and the local environment of the catalysts thus enhancing the eCO2R performance. In conclusion, the shortcomings and pivotal requirements in this field have been discussed in this perspective.

Two new compounds in the Yb–Cu–Ga system were discovered. Yb6(CuGa)50 was obtained as single crystals grown from gallium metal flux, and Yb6(CuGa)51 was synthesized by high-frequency induction heating technique. Structure analysis reveals new structure type for Yb6(CuGa)50 (C2/m space group), while Yb6(CuGa)51 crystallizes in rhombohedral space group R3m adopting the Th2Zn17 structure type. Both structures could be derived from the simplest layered packing, through CaCu5-type structure, as a common parent. Physical properties of the Yb6(CuGa)51 sample obtained bulk quantity were explored. The magnetic susceptibility study of Yb6(CuGa)51 in the temperature range of 2–300 K suggests a valence fluctuation at lower temperatures. X-ray absorption near edge spectroscopy suggests that Yb exists in mixed-valent state in Yb6(CuGa)51. Electrical resistivity measurement reveals that Yb6(CuGa)51 is metallic in nature and shows Fermi-liquid behavior in the temperature range from 3.5 to 25 K.

Catalytic conversion of CO2 to chemicals and fuels is a “two birds, one stone” approach toward solving the climate change problem and energy demand–supply deficit in the modern world. Recent advances in mechanistic insights and design of suitable catalysts for direct thermocatalytic hydrogenation of CO2 to C1 products are thoroughly discussed in this Review. The role of catalyst composition and process conditions in determining the selective pathways to various products like carbon monoxide, methanol, methane, and dimethyl ether has been overviewed in light of thermodynamic and kinetic considerations. After extensive elaboration of the main motivation of the reaction pathways, catalytic roles, and reaction thermodynamics, we summarize the most important macroscopic aspects of CO2 hydrogenation technology development, which include reactor innovations, industrial status of the technology, life cycle assessment and technoeconomic analysis. Finally, a critical perspective on the future challenges and opportu...

We have synthesized ordered NixSny nanoparticles separated by Al2O3 as highly efficient catalysts for the vapor phase hydrogenation of furfural. The NixSny-Al2O3 composite catalysts with different chemical compositions (Ni3Sn4, Ni3Sn, Ni1.5Sn, Ni3Sn2, Ni) were prepared through the layered double hydroxide (LDH) route by annealing at 800 °C in the presence of H2. NixSny nanoparticles were well dispersed throughout the Al2O3 matrix indicating the high thermal stability of these materials. The effect of different concentration of Ni, Sn, and Al in the formation of NixSny-Al2O3 catalyst was investigated. The X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure analyses indicate the formation of intermetallic phases with spherical particles having an average size of 30–160 nm. The nanoparticles with different compositions were tested toward the hydrogenation of furfural, and it was found that crystal structure, atomic ordering and composition play crucial roles in the cataly...

We report a detailed experimental and theoretical investigation of structural, optical, magnetic and magnetothermal properties of single crystals of a new organic-inorganic hybrid (C2H5NH3)2CoCl4. Grown by slow evaporation method at room temperature, the compound crystallizes in centrosymmetric orthorhombic structure (Pnma) which undergoes a reversible phase transition at 235/241 K (cooling/heating) to noncentrosymmetric P212121 space group symmetry associated with order-disorder transformation of carbon atoms of the ammonium cations as well as molecular rearrangement. Electronic absorption spectra of the compound are typical of geometrically distorted [CoCl4]2- tetrahedra having spin-orbit coupling effect. The isolated nature of [CoCl4]2- tetrahedra in the crystal reflect in paramagnetic behaviour of the compound. Interestingly, field induced spin flipping behaviour is observed at low temperature. First principles density functional calculations reveal weak magnetic interaction among cobalt spins with ferromagnetic state being the ground state. The entropy change associated with the spin flipping has been experimentally estimated by magnetic and heat capacity measurements which has a maximum value of 16 J Kg−1 K−1 at 2.5 K under 7 T magnetic field. To the best of our knowledge, this is the first report on magnetocaloric effect observed in an organic-inorganic halide compound. The estimated value is sizable and is comparable to that of well-known transition metal molecular cluster magnets Mn12 or Fe14. The overall findings promise to enlighten new routes to design and constitute multifunctional organic-inorganic halide materials.

We elucidate real-time mechanistic insights into the promotional effect of Ni substitution on the bifunctional overall water splitting (OWS) activity of molybdenum and tungsten carbides (Ni-MoC/WC@NGC) supported on N-doped graphitic carbon (NGC). Ni substitution yields multi-fold improvement in OWS over the pristine systems that are comparable to commercial Pt/C for hydrogen evolution reaction (HER) and better than IrO2 for oxygen evolution reaction (OER). Ni-MoC@NGC champions in HER activity exhibiting an onset overpotential of 65 mV and current density of 140 mA/cm2 at −370 mV (v RHE) in acidic media. An H2O electrolyzer constructed with Ni-MoC@NGC shows a comparable cell voltage to the PtǁIrO2 pair and could split water aided by 1.5 V AAA commercial battery. First principle calculations and in-situ probing through quick-XAS during electrochemical processes provide valuable insights into how the adsorption energies of intermediates and reaction kinetics are modulated at different catalytic sites with the promotional electronic effect of Ni.

The catalytic properties of the materials can be altered with different arrangements of atoms, either in ordered or disordered manner. To study this behavior in detail, we have selected compounds based on Pd and Cu with different atomic arrangements and phase distribution. Nanoparticles of Pd1-xCux with different atomic ratios and phase states are obtained by a facile one pot solvothermal method. The multiple combinations of structurally ordered and disordered phases are tuned by optimizing several synthetic strategies, which are qualitatively and quantitatively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and transmission electron microscopy measurements. Electrocatalytic ethanol oxidation reaction (EOR) is carried out in alkaline medium for all these synthesized Pd1-xCux nanoparticles. It is observed that the EOR activity and stability are enhanced in comparison to the commercial Pd/C catalyst, which can be attributed to the atomic ordering and compressive strain introduced upon optimized phase distribution.

Over the last 3-4 decades, solid-state chemistry has emerged as the forefront of materials design and development. The field has revolutionized into a multidisciplinary subject and matured with a scope of new synthetic strategies, new challenges, and opportunities. Understanding the structure is very crucial in the design of appropriate materials for desired applications. Professor Mercouri G. Kanatzidis has encountered both challenges and opportunities during the course of the discovery of many novel materials. Throughout his scientific career, Mercouri and his group discovered several inorganic compounds and pioneered structure-property relationships. We, a few Ph.D. and postdoctoral students, celebrate his 60th birthday by providing a Viewpoint summarizing his contributions to inorganic solid-state chemistry. The topics discussed here are of significant interest to various scientific communities ranging from condensed matter to green energy production.

Facile and efficient ball milling and polyol methods were employed for the synthesis of nickel selenide (NiSe) nanoparticle. The particle size of the NiSe nanoparticle has been controlled mechanically by varying the ball size in the milling process. The role of the surfactants in the formation of various morphologies was studied. The compounds were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (EDS). The efficiency of the NiSe nanoparticle as a catalyst was tested for the reduction of para-nitroaniline (PNA) to para-phenyldiamine (PPD) and para-nitrophenol (PNP) to para-aminophenol (PAP) using NaBH 4 as the reducing agent. Particle size, morphology and the presence of surfactant played a crucial role in the reduction process.

International audience; Temperature and magnetic field dependent resistivity studies of topological insulating materials Bi2Te2Se, Sb2Te2Se and Bi2Te2S are examined using various transport characteristics with suitable XRD and Raman structural analyses. The longitudinal resistivity data with decreasing of temperature reveals the insulating phase in Bi2Te2Se and showed profound metallic nature in Sb2Te2Se and Bi2Te2S. We observed a bulk hole carrier concentration of 0.8 × 1019 cm−3 through Hall coefficient study for the compound Sb2Te2Se, whereas Bi2Te2S exhibit an electron carrier density of 0.3 × 1019 cm−3 at 2 K and 9 T. Magnetoresistance results suggest a residual carrier effect from these polycrystalline topological compounds would degrade the actual experimental observation of surface state, instead, bulk insulating behaviour has been realized. With controllable bulk carrier effect, a single crystal approach may unleash the definite Dirac surface state with absence of impurity scattering over topological characteristics.

The present study reports the effect of Sn substitution on the structural and thermoelectric properties of synthetic tetrahedrite (Cu12Sb4S13) system. The samples were prepared with the intended compositions of Cu12Sb4-xSnxS13 (x = 0.25, 0.35, 0.5, 1) and sintered using spark plasma sintering. A detailed structural characterization of the samples revealed tetrahedrite phase as the main phase with Sn substituting at both Cu and Sb sites instead of only Sb site. The theoretical calculations using density functional theory revealed that Sn at Cu(1) 12d or Cu(2) 12e site moves the Fermi level (E-F) toward the band gap, whereas Sn at Sb 8c site introduces hybridized hole states near E-F. Consequently, a relatively high optimum power factor of 1.3 mW/mK(2) was achieved by the x = 0.35 sample. The Sn-substituted samples exhibited a significant decrease in the total thermal conductivity (kappa(T)) compared to the pristine composition (Cu12Sb4S13), primarily because of reduced electronic thermal conductivity. Due to an optimum power factor (1.3 mW/mK(2)) and reduced thermal conductivity (0.9 W/mK), a maximum zT of 0.96 at 673 K was achieved for x = 0.35 sample, which is nearly 40% increment compared to that of the pristine (Cu12Sb4S13) sample.

Correction for ‘Conductive interface promoted bifunctional oxygen reduction/evolution activity in an ultra-low precious metal based hybrid catalyst’ by Shreya Sarkar et al., Chem. Commun., 2021, 57, 1951–1954, DOI: 10.1039/D0CC08225B.

The consequences of increase in CO2 concentration in atmosphere are well known to scientists, politicians and policy makers. These effects can be foreseen in near future, bringing a serious concern and responsibility to the research community to find efficient and potential solutions to deal with it. Furthermore, use of fossils to fulfill the extensive energy requirements worldwide is majorly responsible for rapidly rising CO2 levels. Therefore, CO2 capture in unconventional reservoirs by injection and displacement of oil and gas either in supercritical state or liquid state is a potential method to permanently capture a significant volume of CO2. In larger picture, this strategy can substantially contribute in the mitigation of global warning. This review presents some useful aspects of CO2 sequestration in unconventional reservoirs i.e. in form of gas hydrates, shale reservoirs and in coalbeds. Here we explain in-depth mechanisms involved in gas production, adsorption/desorption, diffusion, gas migration and expansion/shrinkage in a given matrix. The review also includes the pathways involved in displacement of oil and gas by CO2, challenges involved in this process and how enhanced recovery of oil and gas can be achieved. This process solves the following challenges worldwide (i) rising levels of CO2, (ii) continuous rise in energy demand (iii) replacement of limited conventional resources (iv) worldwide distribution of unconventional reservoirs (v) eliminating the geopolitical conflicts with minimal harmful effects towards environmental and human health. This review presents collective information about the parameters responsible for enhanced oil and gas recovery.

We synthesize single-crystals of ScPdBi, a Half-Heusler compound by self-flux growth technique and report its physical properties such as magneto-transport and specific heat down to 2 K. Resistivity measurements were performed on these single-crystals at ambient and high-pressure conditions. Temperature-dependent resistivity measurements reveal that ScPdBi shows the metallic character at ambient pressure and without applied magnetic field. The metallic character of ScPdBi was un-altered even in extreme conditions such as high pressure (up to 19 GPa) and magnetic field (up to 9 T). We observe an upturn in the resistivity which persists even at high pressure. We rule-out the presence of the Kondo effect by performing the specific heat measurements down to 2 K which resulted in a low Sommerfeld coefficient (γ ≈ 2.6 ± 0.9 mJ mol−1 K−2). This anomaly in resistivity below 30 K could be attributed to an electron-hole scattering process or a carrier imbalance effect.

Ordered intermetallic Pt 2 In 3 nanoparticles have been synthesized by superhydride reduction of K 2 PtCl 4 and InCl 3 . x H 2 O precursors using facile, one-pot solvothermal method. We report surfactant free solvothermal synthesis of a novel ordered Pt 2 In 3 intermetallic nanoparticles for the first time. The structure and morphology of the catalyst has been confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive spectrometry and X-ray photoelectron spectroscopy. The electrocatalytic properties of the catalysts have been investigated by cyclic voltammetry and chronoamperometry. The as prepared Pt 2 In 3 catalyst exhibit far superior electrocatalytic activity and stability towards alcohol oxidation over commercial Pt/C. The specific activity of as synthesized catalyst was found to be ~3.2 and ~2.3 times higher than commercial Pt/C for methanol and ethanol oxidation, respectively. This improved activity and durability of the Pt 2 In 3 nanoparticles can make the catalyst an ideal catalyst candidate for direct alcohol fuel cell.

Single crystals (SCs) of the compounds Eu3Ag2In9 and EuCu2Ge2 were synthesized through the reactions run in liquid indium. Eu3Ag2In9 crystallizes in the La3Al11 structure type [orthorhombic space group (SG) Immm] with the lattice parameters: a = 4.8370(1) A, b = 10.6078(3) A, and c = 13.9195(4) A. EuCu2Ge2 crystallizes in the tetragonal ThCr2Si2 structure type (SG I4/mmm) with the lattice parameters: a = b = 4.2218(1) A, and c = 10.3394(5) A. The crystal structure of Eu3Ag2In9 is comprised of edge-shared hexagonal rings consisting of indium. The one-dimensional chains of In6 rings are shared through the edges, which are further interconnected with other six-membered rings forming a three-dimensional (3D) stable crystal structure along the bc plane. The crystal structure of EuCu2Ge2 can be explained as the complex [CuGe](2+δ)– polyanionic network embedded with Eu ions. These polyanionic networks present in the crystal structure of EuCu2Ge2 are shared through the edges of the 011 plane containing Cu and Ge ...

The compounds Eu 5 In 2 Sb 6 and Yb 5 X 2 Sb 6 ( X = Al, Ga and In) have been synthesized by high frequency induction heating method. The compounds Eu 5 In 2 Sb 6 and Yb 5 X 2 Sb 6 crystallize respectively in the orthorhombic Ca 5 Ga 2 As 6 and Ba 5 Al 2 Bi 6 structure types, space group Pbam . The crystal structure of all the four compounds can be envisaged as a composition of infinite one dimensional [ X 2 Sb 6 ] 10− double chains arranged in parallel fashion along the [110] plane. The oxidation state of the rare earth atom has been deduced from the bond valence sum calculation on the structural data. The deduced values are found to corroborate well with the values that obtained from the magnetic susceptibility and the X-ray absorption near edge spectroscopy.

A novel solvothermal method has been used for the synthesis of porous ellipsoidal GeO2 particles with oleic acid and oleylamine as solvent and co-surfactant, respectively and its performance has been studied as an anode material for Li ion battery applications. The presence of highly hydrophobic oleic acid and oleylamine on the surface of the as synthesized sample imparts a detrimental effect on its performance. Although removal of the capping agents with glacial acetic acid improves the performance to some extent, a drastic enhancement in both the specific capacity and cycling stability is observed when the nanoparticles are wrapped with rGO/PANI composites at low temperature.

Ordered intermetallic nanocrystals with high surface area are highly promising as efficient catalysts for fuel cell applications because of their unique electrocatalytic properties. The present work discusses about the controlled synthesis of ordered intermetallic Pd 3 Pb nanocrystals in different morphologies at relatively low temperature for the first time by polyol and hydrothermal methods both in presence and absence of surfactant. Here for the first time we report surfactant free synthesis of ordered flower-like intermetallic Pd 3 Pb nanocrystals in 10 s. The structural characteristics of the nanocrystals are confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The as synthesized ordered Pd 3 Pb nanocrystals exhibit far superior electrocatalytic activity and durability towards formic acid and ethanol oxidation over commercially available Pd black (Pd/C). The morphological variation of nanocrystals plays a crucial role in the electrocatalytic oxidation of formic acid and ethanol. Among the catalysts, the flower-like Pd 3 Pb shows enhanced activity and stability in electrocatalytic formic acid and ethanol oxidation. The current density and mass activity of flower-like Pd 3 Pb catalyst are higher by 2.5 and 2.4 times than that of Pd/C for the formic acid oxidation and 1.5 times each for ethanol oxidation.

Rare earth (RE) based intermetallic compounds (IMCs) show wide range of fascinating and anomalous physical properties due to the interplay of various kinds of interactions between the localized 4f electrons of the RE atoms and the delocalized conduction electrons. Among them, the Eu containing compounds have particular scientific interest because they can exhibit two energetically similar electronic configurations: Eu2+ (4f7) and Eu3+ (4f6). This feature of Eu resulted in compounds with different structures or even new structure types compared to other RE based intermetallics. In this review, we discuss about the Eu based ternary intermetallic compounds with a focus on the crystal structure and structural relationship of Eu based ternary IMCs with known structures and finally novel structure types.

We report the structural, vibrational, and electrical transport properties up to $\ensuremath{\sim}16\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ of $1T\text{\ensuremath{-}}\mathrm{TiT}{\mathrm{e}}_{2}$, a prominent layered 2D system. We clearly show signatures of two isostructural transitions at $\ensuremath{\sim}2\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and $\ensuremath{\sim}4\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ obtained from the minima in $c/a$ ratio concomitant with the phonon linewidth anomalies of ${E}_{g}$ and ${A}_{1g}$ modes around the same pressures, providing a strong indication of unusual electron-phonon coupling associated with these transitions. Resistance measurements present nonlinear behavior over similar pressure ranges shedding light on the electronic origin of these pressure-driven isostructural transitions. These multiple indirect signatures of an electronic transition at $\ensuremath{\sim}2\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and $\ensuremath{\sim}4\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ are discussed in connection with the recent theoretical proposal for $1T\text{\ensuremath{-}}\mathrm{TiT}{\mathrm{e}}_{2}$ and also the possibility of an electronic topological transition from our electronic Fermi surface calculations. Between 4 GPa and $\ensuremath{\sim}8\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, the $c/a$ ratio shows a plateau suggesting a transformation from an anisotropic 2D layer to a quasi-3D crystal network. First-principles calculations suggest that the 2D to quasi-3D evolution without any structural phase transitions is mainly due to the increased interlayer Te-Te interactions (bridging) via the charge density overlap. In addition, we observed a first-order structural phase transition from the trigonal ($P\overline{3}m1$) to monoclinic ($C2/m$) phase at higher pressure regions. We estimate the start of this structural phase transition to be $\ensuremath{\sim}8\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and also the coexistence of two phases [trigonal ($P\overline{3}m1$) and monoclinic ($C2/m$)] was observed from $\ensuremath{\sim}8\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ to $\ensuremath{\sim}16\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$.

ACS energy letters 3(12), 3008 - 3014 (2018). doi:10.1021/acsenergylett.8b01965, Since the preceding decade, strain engineering has been playing a vital role in modifying the activity of electrocatalysts. Incorporation of tensile strain into a Pd-based system usually requires substitution with larger atoms (usually a third row expensive transition metals). This work provides a unique strategy of introducing tensile strain by the substitution of small and low cost copper atoms (inverse strain effect) at the palladium sites of Pd$_{17}$Se$_{15}$. The Pd atom being in the +2 oxidation state adsorbs hydrogen very weakly, and Se, in its elemental state, binds weakly to H* adsorbate. However, the presence of Pd modulates the electronic structure of Se to have $ΔG_{H*}$ close to 0 and favors the progress of the reaction. Cu substitution further lowers $ΔG_{H*}$, thus favoring the reaction. This unique synergistic effect between the two processes is accountable for better activity, high stability of 30 000 cycles and significantly high turnover frequency of 126.3 s$^{–1}$ for (CuPd)$_{17}$Se$_{15}$., Published by American Chemical Society, Washington, DC

We have synthesized the compounds RE2AgGe3 (RE =Ce, Pr, Nd) by arc melting. The crystal structure obtained from single crystal and powder X-ray diffraction suggests that these compounds crystallize in the α-ThSi2 structure type. The magnetic susceptibility data of Ce2AgGe3 follows Curie–Weiss (CW) law above 25 K without any magnetic ordering down to 2 K. The effective magnetic moment (μeff) was calculated as 2.53 μB/Ce and negative Curie paramagnetic temperature (θp)=−2.4 K hint weak antiferromagnetic coupling among the adjacent spins. Pr2AgGe3 shows a complex magnetic behavior wherein the magnetic susceptibility at field cooled and zero field cooled modes bifurcates at 11.5 K with the latter undergoing a cusp like maxima, probably due to weak ferromagnetic interaction. The θp and μeff obtained are 4 K and 4.33 μB/Pr, respectively. Nd2AgGe3 undergoes multiple magnetic transitions. Temperature dependent resistivity data reveals that three compounds are metallic in nature.

A new compound Eu{sub 2}Pt{sub 3}Si{sub 5} with plate shaped morphology has been grown from excess In flux. The compound crystallizes in the orthorhombic U{sub 2}Co{sub 3}Si{sub 5} structure type, Ibam space group and the lattice parameters are a=10.007(2) A, b=11.666(2) A and c=6.0011(12) A. The crystal structure of this compound can be conceived as inter-twinned chains of [Pt{sub 2}Si{sub 2}] and [PtSi{sub 3}] tetrahedra connected along [100] direction to give rise to a complex three dimensional [Pt{sub 3}Si{sub 5}] network. Temperature dependent magnetic susceptibility data suggests that Eu{sub 2}Pt{sub 3}Si{sub 5} undergoes a strong antiferromagnetic ordering (T{sub N}=19 K) followed by a weak ferromagnetic transition (T{sub C}=5.5 K). The effective magnetic moment/Eu obtained from susceptibility data is 6.78 μ{sub B} accounts mixed valent Eu with almost 85% divalent Eu, which is supported by X-ray absorption near edge spectroscopy. The compound undergoes a metamagnetic transition under applied magnetic field through a probable spin flop mechanism. - Graphical abstract: Eu{sub 2}Pt{sub 3}Si{sub 5}, a new member in the U{sub 2}Co{sub 3}Si{sub 5} (Ibam) family undergoes metamagnetic transition at high magnetic field and Eu is in mixed valence state. - Highlights: • A new compound Eu{sub 2}Pt{sub 3}Si{sub 5} has been synthesizedmore » using indium as an inactive metal flux. • The compound undergoes metamagnetic transition at higher field. • Eu in this compound resides in a mixed valence state.« less

Structural analysis of the room temperature diffraction data of Nd 2 NiGe 3 shows that it exhibits AlB 2 type structure with space group P 6/ mmm . The crystal structure of Nd 2 NiGe 3 consists of two dimensional Ni/Ge hexagonal units sandwiching the neodymium atoms between them. Temperature dependent magnetic susceptibility data follows Curie–Weiss law in the temperature range 20–300 K yielding an effective magnetic moment of 3.83 μ B /Nd and paramagnetic Curie temperature −2.1 K indicating trivalent Nd and weak antiferromagnetic interactions, respectively. Low field magnetic susceptibility measurement show a weak antiferromagnetic like ordering around 3 K. Temperature dependent neutron diffraction measurements rules out long range antiferromagnetic ordering in this compound. The electrical resistivity measurement shows metallic nature of Nd 2 NiGe 3 , which exhibits sudden drop in resistivity below 3 K.

The compound EuAg4In8 has been obtained as single crystals in high yield from reactions run in liquid indium. X-ray diffraction on single crystals suggests that EuAg4In8 crystallizes in the CeMn4Al8 structure type, tetragonal space group I4/mmm with lattice constants a=b=9.7937(2) A and c=5.7492(2) A. Crystal structure of EuAg4In8 is composed of pseudo Frank–Kasper cages occupied by one europium atom in each ring, which are shared through the corner along the ab plane resulting in a three dimensional network. The magnetic susceptibility of EuAg4In8 was measured in the temperature range 2–300 K, which obeyed Curie–Weiss law above 50 K. Magnetic moment value calculated from the fitting indicates the presence of divalent europium, which was confirmed by X-ray absorption near edge spectroscopy. Electrical resistivity measurements suggest that EuAg4In8 is metallic in nature with a probable Fermi liquid behavior at low temperature.

A [2 + 2] Schiff base type condensation between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAP) and 1,3,6,8-tetrakis (4-formylphenyl) pyrene (TFFPy) under solvothermal condition yields a crystalline, quasi-two-dimensional covalent organic framework (SB-PORPy-COF). The porphyrin and pyrene units are alternatively occupied in the vertex of 3D triclinic crystal having permanent microporosity with moderately high surface area (∼869 m2 g–1) and promising chemical stability. The AA stacking of the monolayers give a pyrene bridged conducting channel. SB-PORPy-COF has been exploited for metal free hydrogen production to understand the electrochemical behavior using the imine based docking site in acidic media. SB-PORPy-COF has shown the onset potential of 50 mV and the Tafel slope of 116 mV dec–1. We expect that the addendum of the imine based COF would not only enrich the structural variety but also help to understand the electrochemical behavior of these class of materials.

A detailed study has been done on the combined effect of the reaction time and the effect of surfactants namely, polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide in the formation of ordered (Ag3In) and disordered (Ag0.75In0.25) phases. The catalytic activity of the samples has been checked for the reduction of para-nitrophenol (PNP) to para-aminophenol (PAP) using NaBH4 as the reducing agent. Ag3In obtained at shorter period using PVP as the surfactant showed better catalytic activity with a rate constant of 8.4 × 10−3 s−1 followed by a substantial decrease to 1.83 × 10−3 s−1 for the sample obtained at longer period. The observed trends in the catalytic activity have been explained based on the ordered–disordered structural transition, particle agglomeration and different stoichiometric ratios of Ag to In.

We report the crystallographic properties of RE2NiGe3 (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er2RhSi3 type structure having hexagonal space group P 6¯2c. In the crystal structure of RE2NiGe3, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (To=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at T

Sm3Ni5Al19 was obtained as large rod shaped single crystals from reactive aluminium flux. Single crystal X-ray diffraction suggests that Sm3Ni5Al19 crystallizes in the Gd3Ni5Al19 structure type, orthorhombic space group Cmcm and lattice constants a = 4.0974(1) A, b = 16.0172(6) A and c = 27.0774(10) A. Sm3Ni5Al19 is a member of the Sm2n+mNi4n+mAl15n+4m series with n = 1 and m = 1. The crystal structure of Sm3Ni5Al19 consists of SmNiAl4 and Sm2Al4Al15 slabs intergrown along the b-axis. Magnetic susceptibility data on Sm3Ni5Al19 confirms the paramagnetic nature with a complicated magnetic ordering below 18 K. The inverse susceptibility data follows modified Curie-Weiss law above 150 K with effective magnetic moment 1.3 μ B/Sm atoms suggests trivalent Sm atoms.

We investigate the structural and magnetic properties in the polymorphs of a new compound CeRh0.5Ge1.5. Depending upon the starting materials, and the slightly different synthesis method, we find that CeRh0.5Ge1.5 compound exists in two different space groups. The first compound, α-CeRh0.5Ge1.5 crystallizes in tetragonal α-ThSi2 structure type in space group I41/amd with lattice parameters, a=4.2034(6) A and c=14.770(3) A. In this structure, the cerium atoms occupy the position between the Rh/Ge tetrahedral layers. On the other hand, the second compound, namely β-CeRh0.5Ge1.5 crystallizes in the AlB2 type hexagonal structure in space group P6/mmm, with lattice parameters, a=4.2615(7) A and c=4.1813(9) A. The crystal structure of β-CeRh0.5Ge1.5 consists of two dimensional Rh/Ge hexagonal units and the cerium atoms are sandwiched between them. Magnetization studies exhibit magnetic ordering, as evident from a sharp peak in the plot of magnetic susceptibility measured as a function of temperature in a fixed magnetic field, in α-CeRh0.5Ge1.5 and β-CeRh0.5Ge1.5 at 3.6 K and 12 K, respectively. Structural and magnetic properties of both compounds are presented and discussed here.

The Yb 2 CuGe 6 and Yb 3 Cu 4 Ge 4 compounds were synthesized from reaction mixtures using indium as flux. Both powder and single crystal X-ray diffraction data were used to refine the crystal structures. Yb 2 CuGe 6 crystallizes in the monoclinic space group C 2/ m in the La 2 AlGe 6 type structure. The lattice parameters are a = 8.0011(16) A, b = 8.1962(16) A, c = 10.682(2) A and β = 100.63(3). The crystal structure of Yb 2 CuGe 6 can be described as the intergrowth of fragments Ge dimmers and zig–zag Ge chains. Yb 3 Cu 4 Ge 4 crystallizes in the orthorhombic space group Immm in the Gd 3 Cu 4 Ge 4 type structure. The lattice parameters are a = 4.1302(8) A, b = 6.5985(13) A and c = 13.691(3) A. X-ray absorption near edge spectroscopy (XANES) measurements indicate that Yb in Yb 2 CuGe 6 and Yb 3 Cu 4 Ge 4 exists as intermediate and trivalent states, respectively. The structural refinement of Yb 2 CuGe 6 is corroborated by total energy calculations within the local density approximation.

The compounds CeGa2 ,C e 0.82Mg0.50Ga1.68, Eu(Mg/Li)xGa2� x (0 6 x 6 0.4) and Eu(Mg/Li)xGa4� x (0 6 x 6 0.73) were synthesized and characterized by X-ray diffraction. CeGa2 and Ce0.82Mg0.50Ga1.68 crystallize in the AlB2 structure type with P6/mmm space group. The structure is composed of infinite arrays of planar hexagonal Ga atoms stacked along the [0 0 1] direction and the Ce atoms are sandwiched between them. Eu(Mg/Li)xGa2� x (0 6 x 6 0.4) crystallize in the KHg2 structure type with Imma space group and consists of the hexagonal rings of M (Li/Mg + Ga) atoms connected along the [1 0 0] plane forming a puckered network with voids occupied by two Eu atoms. The Eu(Mg/Li)xGa4� x (0 6 x 6 0.73) compounds crystallize in the BaAl4 structure type having I4/mmm space group. In Eu(Mg/Li)xGa4� x, the Eu atom occupies the edge and the body centered position of the unit cell while the Ga and M (Li/Mg + Ga) atoms forms a 3D polyanionic framework. Magnetic susceptibility of CeGa2, EuGa2, EuGa4 and their corresponding Li/Mg analogs are discussed.

High quality single crystals of SmCu6In6 were obtained from the reactions run in excess liquid indium and characterized by means of single crystal X-ray diffraction data. SmCu6In6 crystallizes in the YCu6In6 structure type, tetragonal space group I4/mmm and lattice constants are a = b = 9.2036(3) A and c = 5.4232(3) A. SmCu6 − xIn6 + x (x = 0, 1, 2) compounds were obtained using arc melting and characterized using powder X-ray diffraction. Magnetic susceptibility data follow modified Curie–Weiss law behaviour above 50 K and the experimentally measured magnetic moment values in SmCu4In8, SmCu5In7 and SmCu6In6 are 0.83 μ B, 1.45 μ B and 0.90 μ B per Sm atom, respectively. SmCu5In7 and SmCu6In6 compounds show antiferromagnetic ordering at T N = 7.8 K, and no magnetic ordering was observed for SmCu4In8 down to 2 K. Electrical resistivity measurements show that all compounds are of metallic nature.

Unspecific peroxygenases (EC 1.11.2.1) represent a group of secreted heme-thiolate proteins that are capable of catalyzing the mono-oxygenation of diverse organic compounds, using only H2O2 as a co-substrate. Here we show that the peroxygenase secreted by the fungus Agrocybe aegerita catalyzed the oxidation of 20 different alkenes. Five branched alkenes, among them 2,3-dimethyl-2-butene and cis-2-butene, as well as propene and butadiene were epoxidized with complete regioselectivity. Longer linear alkenes with a terminal double bond (e.g. 1-octene) and cyclic alkenes (e.g. cyclohexene) were converted into the corresponding epoxides and allylic hydroxylation products; oxidation of the cyclic monoterpene limonene yielded three oxygenation products (two epoxides and an alcohol). In the case of 1-alkenes, the conversion occurred with moderate stereoselectivity, in which the preponderance for the (S)-enantiomer reached up to 72% ee for the epoxide product. The apparent Michaelis-Menten constant (Km) for the epoxidation of the model substrate 2-methyl-2-butene was 5mM, the turnover number (kcat) 1.3×10(3)s(-1) and the calculated catalytic efficiency, kcat/Km, was 2.5×10(5)M(-1)s(-1). As epoxides represent chemical building blocks of high relevance, new enzymatic epoxidation pathways are of interest to complement existing chemical and biotechnological approaches. Stable and versatile peroxygenases as that of A. aegerita may form a promising biocatalytic platform for the development of such enzyme-based syntheses.

The high quality single crystals of Yb5Co4Ge10 have been grown by the indium metal flux method and characterized by means of single crystal X-ray diffraction data. Yb5Co4Ge10 crystallizes in the Sc5Co4Si10 structure type, tetragonal space group P4/mbm and lattice constants are a = b = 12.6369(18) ? and c = 4.1378(8) ?. Crystal structure of Yb5Co4Ge10 composed of three-dimensional [Co4Ge12] network having five, six and eight membered rings. The three non-equivalent Yb atoms are sandwiched in three different channels created by the [Co4Ge12] network. Based on the bond length analysis from the crystallographic information, we confirmed that Yb1 and Yb2 atoms are in the trivalent magnetic state and Yb3 is in the divalent non-magnetic state.

This article covers the use of indium as a potential metal solvent for the crystal growth of europium and ytterbium-based intermetallic compounds. A brief view about the advantage of metal flux technique and the use of indium as reactive and non-reactive flux are outlined. Large single crystals of EuGe2, EuCoGe3 and Yb2AuGe3 compounds were obtained in high yield from the reactions of the elements in liquid indium. The results presented here demonstrate that considerable advances in the discovery of single crystal growth of complex phases are achievable utilizing molten metals as solvents.

Single-phase samples of Yb 4 LiGe 4 and Yb 5 Ge 4 were synthesized using high frequency (HF) heat treatment. Yb 4 LiGe 4 crystallizes in orthorhombic space group Pnma with the Gd 5 Si 4 type of crystal structure and lattice parameters a = 7.0828(3) A, b = 14.6415(7) A, and c = 7.6279(4) A. One Yb position in Yb 5 Ge 4 is substituted by the lithium atom and causes a distortion of the germanium tetragons in Yb 4 LiGe 4 . Investigation of the electronic state of Yb via magnetic susceptibility and X-ray absorption near-edge spectroscopy (XANES) revealed a presence of two electronic states of ytterbium, 4 f 13 and 4 f 14 (mixed valence), in Yb 5 Ge 4 and Yb 4 LiGe 4 . Studies of the temperature dependence of the electrical resistivity, magnetization, 7 Li spin-lattice relaxation rate and the specific heat indicate that strong electronic correlations are present in Yb 4 LiGe 4 , and below approximately 50 K there is a competition between ferromagnetic and antiferromagnetic correlations. Magnetic ordering in Yb 4 LiGe 4 , if present, occurs below the reported antiferromagnetic transition temperature of 1.7 K for Yb 5 Ge 4 .