Br Anions Research Articles

Three-dimensional atomic mapping of ligands on palladium nanoparticles by atom probe tomography

Capping ligands are crucial to synthesizing colloidal nanoparticles with functional properties. However, the synergistic effect between different ligands and their distribution on crystallographic surfaces of nanoparticles during colloidal synthesis is still unclear despite powerful spectroscopic techniques, due to a lack of direct imaging techniques. In this study, atom probe tomography is adopted to investigate the three-dimensional atomic-scale distribution of two of the most common types of these ligands, cetrimonium (C19H42N) and halide (Br and Cl) ions, on Pd nanoparticles. The results, validated using density functional theory, demonstrate that the Br anions adsorbed on the nanoparticle surfaces promote the adsorption of the cetrimonium cations through electrostatic interactions, stabilizing the Pd {111} facets. In contrast, the Cl anions are not strongly adsorbed onto the Pd surfaces. The high density of adsorbed cetrimonium cations for Br anion additions results in the formation of multiple-twinned nanoparticles with superior oxidation resistance.

Tin‐Lead Perovskite Fabricated via Ethylenediamine Interlayer Guides to the Solar Cell Efficiency of 21.74%

AbstractTin‐lead perovskite solar cells (PSCs) show inferior power conversion efficiency (PCE) than their Pb counterparts mainly because of the higher open‐circuit voltage (Voc) loss. Here, it is revealed that the p‐type surface of perovskite transforms to n‐type, based on post‐treatment by a Lewis base, ethylenediamine. This approach forms a graded band structure owing to the rise of the Fermi‐energy level at the surface of the perovskite layer, and increases the built‐in potential from 0.56 to 0.76 V, which increases the Voc by more than 100 mV. It is demonstrated that EDA can lower the defect density (Sn4+ amount) by screening perovskite against oxygen, and by bonding with undercoordinated Sn on the surface. This study further explores the role of Br anion inclusion in the perovskite lattice from the viewpoint of reducing the lattice strain and Urbach energy. Finally, a high Voc of 0.86 V is obtained, corresponding to a voltage deficit of 0.39 V, using a perovskite absorber with a bandgap of 1.25 eV and the highest PCE (21.74%) reported so far for Sn‐Pb PSCs is achieved.

Counterion-specific shale hydration inhibiting performance of vinylimdazolium ionic liquids

The role of cation and the influence of the cation alkyl chain length of vinylimdazolium-based ionic liquid (IL) were studied previously to develop high-performance shale inhibitor for application in water-based drilling fluids (WBDFs). Results demonstrate that they have a considerable effect on the inhibition performance. However, the physicochemical properties can be tuned by changing the cation/anion combination. Therefore, the influence of anion type on the inhibiting performance must be investigated. In this study, we selected several vinylimdazolium-based ILs with different anions, such as bromide (Br−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−), and bis(trifluoromethylsulfonyl) (TFSI−). The size, solubility, hydrophilicity, and interaction in-between were tuned accordingly by changing the anion species. Results from linear swelling height, hot rolling recovery, and rheological measurements show that the IL with bromide anion has the most outstanding shale inhibiting performance. The anions influence the inhibitory performance of ILs in a distinct manner from cations by measuring the properties of Na–Bent dispersions added with different anion-based ILs. The former produces different abilities to suppress electric double layers and decreases the interlayer distance, whereas the latter mainly affects the interlayer distance. Despite different hydrophilic/hydrophobic properties, they have similar performance to inhibit the crystalline hydration and swelling. This condition is probably because they have a common cation that dominates the process of entering the interlayer void and narrowing interlayer spacing. Many hydrophilic ILs with anion Br− or BF4− have the capacity to strongly resist the repel interaction between clay particles and prompt aggregation, leading to better inhibitory performance. Combined with the previous result, cations and anions affect the IL inhibiting ability although their underlying mechanism is different. Thus, this work explored the relationship between inhibiting performance and IL moiety. The findings provide consolidate theoretical foundation for developing shale inhibitors for WBDFs.

In‐Situ and Reversible Enhancement of Photoluminescence from CsPbBr3 Nanoplatelets by Electrical Bias

AbstractIn‐situ and real‐time modulation of the optical properties of semiconductor nanoemitters by a CMOS‐compatible strategy holds great promise for developing functional and integrated optoelectronic devices. Herein, the reversible and giant (>13 times) enhancement of the photoluminescence (PL) from inorganic halide perovskite nanoplatelets by electrical bias is demonstrated for the first time. Based on the comprehensive spectroscopic analysis, the improved PL performance is attributed to the dynamic surface healing effect by bias‐induced ion redistribution. The switching from PL quenching to PL enhancement from CsPbBr3 nanoplatelet is manifested at threshold temperature of ≈190 K. Moreover, the temperature dependent measurements unravel the activation energy of 142.8 ± 31.1 meV, corroborating that the drifted species of anion (Br−) or VBr dominates the trap healing process. Accordingly, a three‐stage defect passivation model of the vertical configuration is established. The synergistic effects of ion redistribution and charge injection caused by thermal equilibrium energy band bending on the optical properties of the perovskite is further investigated by contacting the perovskite with indium tin oxide electrode. These results provide novel insight into the photophysical properties of halide perovskites and are beneficial for display and lighting applications in future, especially on‐chip integrated photonics circuits and systems.

Synthesis of AgNWs using copper bromide as stabilizing agent and oxygen scavenger and their application in conductive thin films

Silver nanowires (AgNWs) have attracted growing interest because of their wide range of applications in modern nano electronic appliances. During polyol method, the presence of cations and anions in the reaction solution has influence on the final morphology of AgNWs. Here we report a feasible way to prepare AgNWs by polyol method. Copper bromide (CuBr2) salt was used to provide anions and cations in the reaction solution. The anions (Br−) helps in reducing the amount of free Ag+ by forming silver bromide (AgBr) during initial silver seeds formation and the cations scavenge oxygen from the surface of AgNWs during preferential growth of the AgNWs. Ethylene glycol (EG) was used as a solvent and reducing agent, silver nitrate (AgNO3) was used as Ag source and polyvinyl pyrrolidone (PVP) was used as a capping agent. The effects of various factors which influence the final morphology of AgNWs were studied. AgNWs were successfully synthesized in the presence of CuBr2 salt. The morphology of the synthesized AgNWs was characterized by the SEM and TEM. The crystallinity was characterized by HRTEM, SAED and XRD. The LSPR peaks of Ag nanostructures were revealed by UV–Vis spectroscopy. The conductive properties of AgNWs thin conductive films were studied by coating the synthesized nanowires on polyethylene terephthalate (PET) substrate.

Perovskite CsPbX3 (X=Cl, Br, I) Nanocrystals in fluorophosphate glasses

For the first time, CsPbX3 (X=Cl, Br, I) nanocrystals (NCs) are synthesized in fluorophosphate glasses. The controlled formation of CsPbX3 quantum dots is realized by adjustment of cooling rate and heat treatment conditions. X-ray diffraction data and optical measurements have confirmed the formation of 4-11 nm sized CsPbX3 nanocrystals. The crystallization of CsPbCl3 is assumed to proceed according to a heterogeneous mechanism, with small CsPbBr NCs acting as nuclei. The introduction of two anions (Cl, Br or Br, I) has results in the appearance of two narrow bands in the luminescence spectra corresponding to quantum dots with different chemical compositions, suggesting that the preparation of NCs with a mixed anion is complicated by phase segregation during the high-temperature synthesis. The photoluminescence of CsPb(Cl, Br)3 quantum dots has a high intensity with a quantum yield of 45-50 % and narrow emission band.

Lead-free tin perovskite solar cells

Summary The development of efficient and stable lead-free perovskite solar cells (PSCs) is crucial for addressing the concern of environmental pollution from the toxic element lead. In recent years, tin PSCs have emerged as a promising candidate for high-performance, eco-friendly photovoltaic technology with a high certified power conversion efficiency (PCE) of more than 11%, indicating a great potential for future applications. Here, we review the recent efficiency progress of tin PSCs based on the equivalent circuit model of solar cells. We then discuss approaches toward efficiency improvement from the device viewpoint, such as optimizing the band gap, increasing the light-harvesting efficiency and carrier diffusion length, surface passivation, and regulating the interface energy-level alignment. Finally, we point out the possibility of reaching 20% PCE for tin PSCs and issues regarding enlarging the cell size and realizing scalable production in the future. We expect that these perspectives will be helpful for accelerating the commercialization of tin PSCs.

Synthesis, molecular structure, and properties of DABCO bromide based ionic liquid combining spectroscopic studies with DFT calculations

Through N-alkylation of 1,4-diazabicyclo [2.2.2] octane with 1-bromooctane a new ionic liquid, namely 1‐octyl‐1,4‐diazabicyclo [2.2.2] octan‐1‐ium Bromide [C8DABCO+][Br−] has been synthesized and characterized by FT-IR, FT-Raman and by 1H and 13C-NMR spectroscopies. Three ionic C-H•••Br bonds were predicted by natural bond orbital (NBO), atoms in molecules (AIM) calculations and bond orders but a monodentate coordination between cation and anion is suggested because only one of them has higher energy and lower distance. The effect of Br on properties of IL is clearly observed by the change in orientation and direction of dipole moment vector in the IL, as compared with the cation. NBO studies reveal that the Br anion strongly stabilizes to cation to form the IL. The complete vibrational assignments of 129 and 132 vibration modes expected for the cation and its IL were performed by using two harmonic force fields with the SQMFF methodology and transferable scaling factors. The scaled harmonic force constants were also reported for both species. The Br confers a higher reactivity to [C8DABCO+][Br−], as suggested by analyses of frontier orbitals. Reasonable correlations were found between the experimental IR, Raman and NMR spectra and the corresponding theoretical ones.

Enhancing the electrochemical performances of LiNi0.8Co0.15Al0.05O2 cathode material by anion/cation co-doping

Layered structure LiNi0.8Co0.15Al0.05O2 (NCA) with high energy density is considered to be the most promising cathode material, but poor structural stability hinders its further development. Here, Na+/Br- co-doped NCA (Na&Br-NCA) was prepared via simple solid phase method. Electrochemical studies showed that cation Na+ doping stabilizes the crystal structure, increases the lattice spacing, and reduces the mixing of cations. Anion Br- doping increases the spacing between the plates and forms a weaker Li-Br bond, which is more conducive to the insertion and extraction of Li+. At 2C, Na&Br-NCA exhibited a reversible capacity of 184.1 mAh g−1 with retention of 91.5% after 100 cycle and a superior rate performance (160.2 mAh g−1 at 5C) compared to pure NCA that showed 180.1 mAh g−1 with retention of 77.7% and 148.6 mAh g−1 at 5C. The results show that Na+/Br- co-doping is beneficial to stabilize the layered structure, reduce polarization, and promote lithium-ion diffusion of Na&Br-NCA. It also provides inspiration for other cation/anion co-doped modified cathode materials.

Simulation and property calculation for FA<sub>1–</sub><i><sub>x</sub></i>Cs<i><sub>x</sub></i> PbI<sub>3–</sub><i><sub>y</sub></i> Br<i><sub>y</sub></i>: Structures and optoelectronical properties

Formamdinium lead triiodide (FAPbI<sub>3</sub>) perovskite has developed as a promising candidate in solar cells for its excellent optoelectronic property. However, the poor environmental stability is still a critical hurdle for its further commercial application. Element doping is an effective method of improving the stability of FAPbI<sub>3</sub> materials. It has been reported that the FA<sub>1–</sub><i><sub>x</sub></i>Cs<i><sub>x</sub></i>PbI<sub>3–</sub><i><sub>y</sub></i>Br<i><sub>y</sub></i> stability for heat and water resistance were greatly improved by Cs cations and Br anions co-doping. In this study, we perform first-principles calculations to systematically investigate the crystal structures, electronic structures, and optical properties of FA<sub>1–</sub><i><sub>x</sub></i>Cs<i><sub>x</sub></i>PbI<sub>3–</sub><i><sub>y</sub></i>Br<i><sub>y</sub></i>. We obtain several stable crystal structures of FA<sub>1–</sub><i><sub>x</sub></i>Cs<i><sub>x</sub></i>PbI<sub>3–</sub><i><sub>y</sub></i>Br<i><sub>y</sub></i> (<i>x</i> = 0.125, <i>y</i> = 0—0.6) in the cubic phase for different ratios of Cs cations to Br anions. By analyzing the structures of these mixed ion perovskites, it is revealed that the lattice parameters decrease linearly with the increase of concentration of Cs cations and Br anions, which is consistent with previous experimental result. In this work, the formation energy difference (∆<i>E</i>) is calculated and our results show that the mixing of Cs cations and Br anions could increase the thermodynamic stability compared with pure FAPbI<sub>3</sub>. The FA<sub>0.875</sub>Cs<sub>0.125</sub>PbI<sub>2.96</sub>Br<sub>0.04</sub> is found to be the most stable in all composites investigated. Furthermore, the band gap, hole and electron effective mass increase with increasing proportion of Br anions, indicating an effective strategy for extending the absorption range of FAPbI<sub>3</sub> perovskites into the ultraviolet of the solar spectrum, thereby affecting the carrier transport mechanism in this material. Density of states (DOS) analysis indicates that the DOS of valence band edge increases with increasing proportion of Br anions and enhancing transitions between the valence and conduction bands. Finally, the absorption rate, carrier collection efficiency, external quantum efficiency, short-circuit current density, open circuit voltage and volt-ampere characteristics for the planar structure perovskite solar cell are analyzed by the equivalent optical admittance method. For the FA<sub>1–</sub><i><sub>x</sub></i>Cs<i><sub>x</sub></i>PbI<sub>3–</sub><i><sub>y</sub></i>Br<i><sub>y</sub></i> (<i>x</i> = 0.125, <i>y</i> = 0.04, thickness = 0.5—1.0 μm) solar cell, the short-circuit current density and the open circuit voltage are estimated at about 24.7 mA·cm<sup>–2</sup> and 1.06 V. It is demonstrated that the co-doping Cs cations and Br anions can improve the stability of the system without reducing short-circuit current density, which may provide some theoretical guidance in preparing the perovskite solar cells with high efficiency and excellent stability.

Importance of Homogeneity in the Solid Electrolyte Interphase for Dendrite-Free Epitaxial Plating of Lithium

Realization of practical rechargeable Li-metal batteries is severely hindered by uncontrolled growth of Li that leads to formation of either dendritic or mossy Li during repeated cycles. These three-dimensional (3D) growth modes of Li induce internal short-circuits, cause loss of Coulombic efficiency and limit the lifetime of the cell. Therefore, a two-dimensional (2D) layer-by-layer deposition of Li is highly desirable for safe and efficient long-term cycling of Li-metal batteries. Existing knowledge on Li dendrite formation suggests that uncontrolled reaction of lithium metal with nonaqueous liquid electrolytes forms an inhomogeneous and mechanically weak solid electrolyte interphase (SEI) layer that results in localized Li-deposition and leads to dendrite-growth on top of the electrode surface. Therefore, in-depth knowledge about structural as well as compositional features of the SEI are vital to suppress dendritic growth and also to realize 2D deposition of Li. However, usually the structure of an SEI is quite complex and heterogeneous. Moreover, the stability of Li-deposition varies with properties of the electrolyte. Since multiple destabilizing factors work together, it is a significant experimental challenge to understand the effects of physical and chemical features of the SEI on the nucleation-and-growth of dendrites. Although considerable improvements have been achieved1, 2 to suppress dendritic growth, microscopically smooth dendrite-free two-dimensional deposition of Li is rare3 and there is no proper know-how to its realization. Herein, we comprehensively examine the role of electrolytes as well as physical and chemical properties of the SEI for layer by layer epitaxial plating of Li.Stripping and plating of Li metal have been investigated in a Li│Separator│Li symmetric-cell configuration using different electrolytes, such as LiTFSI, LiTFSI + LiBr, LiNO3, LiNO3 + LiBr etc. in glyme ether solvents. Morphological analysis has shown that in all the investigated electrolytes except LiNO3 + LiBr/tetraglyme, 3D/dendritic/mossy deposition of Li has been observed. In contrast, specifically in 1 M LiNO3 + 0.05 M LiBr/tetraglyme electrolyte the plating of Li metal has exhibited dendrite-free epitaxial growth up to a thickness of ~ 30 μm which has been confirmed by the scanning electron microscopic (SEM) images and electron backscatter diffraction (EBSD) signal as shown in the Figure. Further mechanistic analyses have revealed that the epitaxial growth of Li metal is benefited from the synergistic effect of the anions Br⁻ and NO3⁻ forming a thin and homogeneous Li2O–rich solid electrolyte interphase (SEI) layer which has been formed during the very first discharge (stripping) process, where the corrosive nature of Br⁻ has removed the original thick passivation layer on pristine Li surface which is then again oxidized (passivated) by the NO3⁻ to prevent further reactions with the electrolyte. As a result, the SEI layer has remained thin due to the electropolishing effect and got ready for the epitaxial electroplating of Li in the following recharge process. Our analyses clearly show that dendrite-free stable Li-deposition is a result of favorable combinations of several competitive factors, such as morphology and chemical composition of the SEI layer as well as conductivity, transference number and the type of counter anion in the electrolyte. Besides, more importantly, we highlight that, in addition to other favorable conditions, spatial homogeneity in the SEI layer in terms of surface roughness, conductivity and chemical composition is an essential requirement for 2D growth of Li.

Breakdown of the linear physical behavior in a solid solution of a halometallate molten salt, (dimim)[Fe(Cl1−xBrx)4] 0 ≤ x ≤ 1

Eighteen samples of the (dimim)[Fe(Cl1−xBrx)4] 0 ≤ x ≤ 1 solid solution were prepared in a one-pot synthesis. Single crystal and synchrotron X-ray powder diffraction studies show that all compounds are isomorphous with an orthorhombic structure (Ama2 space group) at room temperature. The crystal structure of these imidazolium molten salts can be described as layers of (dimim)+ cations (dimim = 1,3-dimethyl-imidazolium) extended in the bc-plane with an antiparallel stacking along the a-axis forming a herring-bond motive. The (FeX4)− (X = Cl and Br) anions form layers extended on the bc-plane that are intercalated between the organic layers and inverted with respect to the adjacent layer along the a direction. The evolution of the cell volume at this temperature follows the Vegard's law in the whole range of substitution with ∆V ≈ 115 Å3 between non-substituted phases, showing a non-linear axial expansion in the b and c directions. In addition, the melting point of the solid solution does not follow the expected linear physical behavior. Finally, the magnetic study indicates the existence of overall antiferromagnetic interactions as predominant, which are stronger with the increase in the (FeBr4)− ion substitution. However, it was found that the 3D magnetic ordering of the non-substituted phases vanishes or it is below the minimum temperature reachable by the magnetometer devices (1.8 K) for the 25–50% bromide substitutions. This is connected with the appearance of different crystal phases as function of bromide composition at low temperature.

A strongly luminescent copper (I) coordination complex with near-unity quantum efficiency

Single crystals of a zero-dimensional (0 D) copper (I) complex 0 D-CuBr(3-picoline)3 (1) has prepared at room temperature. Each molecule of 1 contains one copper ion, which coordinates to three organic ligands and one Br anion. The strong metal-to-ligand charge transfer (MLCT) along with the halide-to-metal charge transfer (XLCT) makes 1 an extremely strong green emitter with near-unity quantum efficiency, exhibiting potential application as lighting materials. Single crystals of a new zero-dimensional (0D) copper (I) complex 0D-CuBr(3-picoline)3 has prepared at room temperature. It serves as an extremely strong green-yellow emitter with near unity quantum efficiency, exhibiting potential application as lighting materials.

Dynamic Changes in Charge Transfer Resistances during Cycling of Aprotic Li-O2 Batteries.

Various electrolyte components have been investigated with the aim of improving the cycle life of lithium-oxygen (Li-O2) batteries. A tetraglyme-based electrolyte containing dual anions of Br- and NO3- is a promising electrolyte system in which the cell voltage during charging is reduced because of the redox-mediator function of the Br-/Br3- and NO2-/NO2 couples, while the Li-metal anode is protected by Li2O formed via the reaction between Li metal and NO3-. To maximize the potential of this system, the fundamental factors that limit the cycle life should be clarified. In the present work, we used nondestructive electrochemical impedance spectroscopy to analyze the temporal change of the charge transfer resistances during cycles of Li-O2 batteries with dual anions. The charge transfer resistance at the cathode was revealed to exhibit good correlation with the reduction of the discharge voltage. These results, combined with the results of electrode surface inspections, revealed that irreversible accumulation of insulating deposits such as Li2O2 and Li2CO3 on the cathode surface was a major cause of the short cycle life. Furthermore, the analyses of the time course of the solution resistance suggested that diminished reactivity between the redox mediators and Li2O2 was a critical factor that led to the irreversible accumulation of the less-reactive Li2O2 on the cathode and eventually to a shortened cycle life. These findings indicated that increasing the reactivity between Br3- and Li2O2 is essentially important for improving the cycle stability of Li-O2 batteries and the reactivity can be nondestructively assessed by tracking the dynamic changes in the solution resistance.

Molecular modeling insights in the extraction of benzene from hydrocarbon stream using deep eutectic solvent

The present study aims to elucidate the molecular insights into the extraction of benzene from hydrocarbon mixture using a phosphonium based deep eutectic solvent (DES). The prepared DES consists of the hydrogen bond acceptor (HBA; methyltriphenylphosphonium bromide, MTPB) and hydrogen bond donor (HBD; ethylene glycol) at a molar ratio of 1:4. The atomic-level classical molecular dynamic (MD) simulation technique is then employed to investigate the equilibrium phase behaviour of the DES + benzene + hexane ternary system with respect to solvent rich and hydrocarbon-rich phases. To observe the effect of feed concentration, three different concentrations were considered from the reported experimental runs, which gave high selectivity and distribution coefficient values. The non-bonded interaction energies of different species and the structural properties such as radial distribution functions, spatial distribution functions (SDFs), and the average number of hydrogen bonds are then computed. It is found that the cation within the HBA, namely, MTP, initiates interactions with benzene when compared to HBD or its anion (Br). MTP and ethylene glycol both are seen to contribute to the hydrogen bonding with benzene, which results in a higher experimental solubility value. The calculations of SDFs further reveal the fact that the benzene molecules are evenly distributed around the active sites of the MTP molecule, whereas hexane molecules are found to be distributed around the non-active sites of the DES. In order to validate the simulation procedure, the concentration in both the phases was compared with the existing LLE experimental results. In the penultimate part, 2D 1H-13C Heteronuclear Multiple Bond Correlation (HMBC) NMR is performed for investigating and confirming the hydrogen bonding interactions among components of DES and benzene.

Large anions induce H2-production from the nitrogenase MoFe proteins of Clostridium Pasteurianum and Azotobacter vinelandii

In the absence of sodium dithionite (DT), addition of the large anions Br−, I− and HS− to the MoFe proteins of Azotobacter vinelandii (Av1) and Clostridium pasteurianum (Cp1) released ~1.0 H2/MoFe protein with an associated increase in the absorbance from 400 to 800 nm, indicative of protein oxidation. The reaction of I− with Cp1 released ~1.0 H2/Cp1 with 0.91 ± 0.12 I−/Mo or 1.82 I−/ Cp1. Oxo anions phosphate, molybdate and ADP also produced ~1.0 H2/ MoFe protein with similar increases in absorbance. H2 was not evolved with Cl− addition but in contrast to other anions, the absorbance decreased from 400 to 800 nm. In the presence of large anions and with excess DT both Cp1 and Av1 slowly evolve H2 through the process of DT reducing oxidized MoFe proteins and anions inducing their oxidation to form H2. The results suggest that anions expose or activate the P centers so their low potential electrons can be transferred to electron acceptors or react with H+ to form H2. Anions could function in a similar manner to the Fe protein in activating P centers to release electron during catalytic activity.

Ionic liquid as adjuvant in an aqueous biphasic system composed of polyethylene glycol for green separation of Pd(II) from hydrochloric solution

An aqueous biphasic system (ABS) is considered to be an environmentally friendly technology for the extraction of diverse substances because the main component of the two phases is water. In this study, extraction behaviors of palladium(II) from hydrochloric solution using a typical polymer/salt ABS with ionic liquid (IL) as an adjuvant were studied. Three imidazolium-based ionic liquids ([Cnmim]Br, n = 4, 6 and 8) were used to tune the properties of the ABS to enhance the extraction performance of Pd(II). The parameters that influence palladium extraction including IL species, IL concentration, salinity, original Pd(II) concentration, equilibrium pH, temperature, and contact time, were systematically studied and discussed. These results demonstrate that incorporating ILs into the PEG2000/salt ABS markedly improved the extraction efficiency, and 96–99% of Pd(II) was distributed into the PEG-rich phase. Among the three imidazolium-based ILs, the maximum extraction efficiency was achieved by the IL that had the shortest alkyl chain attached to the imidazole ring, and it can be interpreted that the electrostatic attraction was the main driving force during Pd(II) extraction. The results of FT-IR and TEM characterization show that the anionic PdCl42− transferred into the PEG-rich phase via anion exchange with the anionic Br− in [C4mim]Br, and the mechanism was confirmed by the stoichiometry of the extracted species of [2C4mim+·PdCl42−]. Hydrazine hydrate (80 wt%) completely reduced Pd(II) in the PEG-rich phase, and EDX and SEM were used to analyze the sediments. The results established that the developed polymer/salt ABS with IL as an adjuvant is a potential environmentally friendly extraction system for palladium recovery from an acidic media.

Tris(2-pyridyl) Bismuthines: Coordination Chemistry, Reactivity, and Anion-Triggered Pyridyl Coupling.

A series of new tris(2-pyridyl) bismuthine ligands of the type [Bi(2-py')3] have been prepared, containing a range of substituents at various positions within their pyridyl rings (py'). They can act as intact ligands or, as a result of the low C-Bi bond energy, exhibit noninnocent reactivity in the presence of metal ions. Structural studies of Li+ and Ag+ complexes show that the coordination to metal ions using their pyridyl-N atoms and to anions using the Lewis acidity of their Bi(III) centers can be modified by the presence of substituents within the 2-pyridyl rings, especially at the 6- or 3-positions, which can block the donor-N or Lewis acid Bi sites. Electron withdrawing groups (like CF3 or Br) can also severely reduce their ability to act as ligands to metal ions by reducing the electron donating ability of the pyridyl-N atoms. Noninnocent character is found in the reactions with Cu+ and Cu2+, resulting in the coupling of pyridyl groups to form bipyridines, with the rate of this reaction being dependent on the anion present in the metal salts. This leads to the formation of Bi(III)/Cu(I) complexes containing hypervalent [X2Bi(2-R-py)]- (X = Cl, Br) anions. Alternatively, the tris(2-pyridyl) bismuthine ligands can act as 2-pyridyl transfer reagents, transferring 2-py groups to Au(I) and Fe(II).

Imaging of the Atomic Structure of All-Inorganic Halide Perovskites.

All-inorganic halide perovskites are promising materials for optoelectronic applications. The surface or interface structure of the perovskites plays a crucial role in determining the optoelectronic conversion efficiency, as well as the material stability. A thorough understanding of surface atomic structures of the inorganic perovskites and their contributions to their optoelectronic properties and stability is lacking. Here we show a scanning tunneling microscopy investigation on the atomic and electronic structure of CsPbBr3 perovskite. Two different surface structures with a stripe and an armchair domain are identified, which originates from a complex interplay between Cs cations and Br anions. Our findings are further supported and correlated with density functional theory calculations and photoemission spectroscopy measurements. The stability evaluation of photovoltaic devices indicates a higher stability for CsPbBr3 in comparison with MAPbBr3, which is closely related to the low volatility of Cs from the perovskite surface.

Europium (III) complexes of amino acid-derived bis-imine-substituted phenanthroline ligands for phosphate recognition

Phenanthroline-based chiral hexadentate ligands L1, L2 and L3, as well as their europium (III) complexes 1–3 are synthesized and characterized. The coordination compounds show strong red emission typical for europium (III) derivatives. Various anionic species, F−, Cl−, Br−, I−, SO42−, NO3−, NO2−, HPO42−, CO32−, HCO3− and OAc−, are employed to evaluate the chemo-sensor properties of the complexes using fluorescence spectroscopy. For complex 1, only the addition of HPO42− leads to quenching of luminescence. For the other complexes 2 and 3, NO2− and HPO42− exhibit a strong response in the emission properties. However, complexes 2 and 3 are found to be more sensitive for HPO42− than for NO2−. The corresponding binding constants (logKβ) of the adducts are determined using the Benesi-Hildebrand method. The described studies show that the europium(III) complexes of the hexadentate ligands L1-3 can be considered as highly specific sensors for the recognition of phosphates with some competition by NO2− ions. While phosphate binding is strong in all three examples, the sensitivity for nitrite increases in the order 1 < 2 < 3. The obtained results are remarkable because the differences are due to less sterically hindered substituents in the periphery of the ligand of 2 and 3, which enable the binding of the small nitrite while the bigger phosphate is bound less tightly.