Microcrystalline Powder Research Articles

Electrochemical Properties of Layered LiMoO<sub>2 </sub>as Cathode for Li-Ion Batteries

With the development of new energy vehicles, it is necessary to develope new fast charging cathode materials for lithium ion batteries. This paper reports a simple carbon thermal reduction routine to synthesize layered LiMoO2 cathode for Li-ion batteries. Impurity-free micro-crystalline powders were synthesized by one-step method with a thermal treatment at 800°C for 5 hrs under N2 atmosphere. The structural, morphological and electrochemical properties of LiMoO2 were characterized by using X-ray diffraction pattern (XRD), scanning electronic microscopy (SEM), charge/discharge cycling and electrochemical impedance spectroscopy (EIS). The diffraction results indicate that the prepared sample has a layered hexagonal structure related to α-NaFeO2. The secondary particles are in order of 2.0 μm length on average with homogeneous distribution. The initial discharge capacity of LiMoO2 is 110.9 mAh·g-1 at 0.1 C, and the capacity can still remain 92.8 mAh·g-1 after 100 cycles. The good cycling performance and high rate discharge performance are attributed to the smaller charge-transfer resistance revealed by EIS results.

Magnetic Fe3O4/ZIF-8 composite as an effective and recyclable adsorbent for phenol adsorption from wastewater

Recovery of phenol in wastewater is a matter of concern. Metal organic frameworks (MOFs) are promising adsorbents for the removal of organic pollutants from water phase owing to their rich pore structure and high chemical activity. However, most MOFs are in the form of microcrystalline powders, making them difficult to be separated and recycled. Therefore, it is important to explore the facile fabrication of magnetic adsorbents with high adsorption efficiency, fast equilibrium adsorption time, and excellent recoverability. A regenerable magnetic Fe3O4/ZIF-8 composite was prepared for phenol removal with ZIF-8 as adsorption mainstay and Fe3O4 nanoparticle as magnetic component. Through self-assembly process design, the advantages of the combination and its synergistic effect were exhibited. The effects of pH, binding time, and initial concentration on the adsorption behaviors of Fe3O4/ZIF-8 towards phenol were investigated to assess adsorption capacity and reusability. Owing to the dual effect of high adsorption activity and abundant pore structures, Fe3O4/ZIF-8 demonstrated prominent adsorption capacity (129.8 mg g−1) and rapid adsorption rate (20 min) towards phenol. The pseudo-second-order kinetic model fits the adsorption data well. The thermodynamic adsorption curves conform to the Langmuir model. The adsorption mechanism involves the critical contribution of hydrogen bonding interaction, π-π interaction, pore adsorption, and electrostatic attraction. Moreover, the magnetic adsorbent shows excellent reusability. This work provides a new sight on the synthesis of high efficiency adsorbents for organic pollutant separation.

Thermal plasma synthesized nano-powders of (LaCe)B6 starting from oxide-based precursors and its field electron emission performance

High temperature synthesis process of microcrystalline and nanocrystalline (LaCe)B6 using Self-propagating High temperature Synthesis (SHS) and arc plasma gas phase condensation methods, respectively have been investigated. These methods are rapid and economically viable processes used for the synthesis of technologically important refractory hexaborides. Microcrystalline powders of (LaCe)B6 were synthesized using the SHS process, starting from oxide precursors of lanthanum, cerium, and boron. The powders obtained using SHS process were used as a precursor to getting nanocrystalline (LaCe)B6 using the thermal plasma route. The thermal plasma synthesis was carried out using nitrogen and argon plasmas, respectively. In-situ plasma diagnostics were used to identify evaporated species and determine plasma temperature during the formation of nanocrystalline (LaCe)B6 using optical emission spectroscopy. Further, an effect of plasma input parameters on the structural and optical properties of as synthesized nanocrystalline (LaCe)6 were investigated using XRD analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. A thorough investigation of morphological and structural properties of synthesized nanocrystalline (LaCe)6 was carried out using transmission electron microscopy. Finally, field effect electron emission properties of the microcrystalline and nanocrystalline product were investigated and current density, turn on field, stability of emission performance were determined.

Tl2[B10H10] und Tl2[B12H12]: Kristallstrukturen, Raman-Spektren und Tl+-Lone-Pair-Lumineszenz im Vergleich

Abstract Thallium(I) decahydro-closo-decaborate Tl2[B10H10] and thallium(I) dodecahydro-closo-dodecaborate Tl2[B12H12] are readily available as microcrystalline powders from reactions of thallium(I) carbonate Tl2[CO3] with aqueous solutions of the respective free acid (H3O)2[B10H10] or (H3O)2[B12H12]. Tl2[B12H12] crystallizes with an anti-fluorite related structure (cubic, F m 3 ‾ $Fm\bar{3}$ , a = 1074.23(8) pm, Z = 4). Each Tl+ cation is coordinated by four icosahedral [B12H12]2– anions (d(B–B) = 180–181 pm) providing a twelvefold coordination sphere of hydrogen atoms (d(Tl–H) = 296 pm). Tl2[B10H10] crystallizes monoclinically in the space group P21/n with a = 704.03(5), b = 1111.45(8), c = 1281.16(9) pm and β = 94.912(3)° for Z = 4. The bicapped square antiprismatic [B10H10]2– anions (d(B–B) = 147–176 pm to the two apical boron atoms, d(B–B) = 161–199 pm within the corpus) again form distorted tetrahedra around the (Tl1)+, but square pyramids around the (Tl2)+ cations. Thus (Tl1)+ is coordinated by 12 hydrogen atoms (d(Tl1–H) = 275–315 pm), but (Tl2)+ only by 11 of them (d(Tl2–H) = 267–357 pm). Both compounds show a greenish-yellow photoluminescence caused by an interconfigurational 6sp –6s 2 emission (3Pn→1S0, n = 0–2) at the Tl+ cation.

Quercetin - based rhodium(III) complex: Synthesis, characterization and diverse biological potentials

Quercetin – based rhodium(III) complex, [RhIIIL2ClH2O], L is quercetin, was synthesized via the direct interaction between the polyphenolic natural product (3,3′,4′,5,7-pentahydroxylflavone) and RhCl3 3H2O. Characterization of the pure isolated metal complex by analytical, electrolytic conductance, TGA and spectroscopic techniques demonstrated the stoichiometric ratio 1:2 metal to ligand. The final structure of [RhIIIL2ClH2O] was confirmed using PXRD–structural analysis by processing the XRD data of microcrystalline powder by the relevant computer program Expo 2014. The mimetic catalytic activity of superoxide dismutase (SOD) was studied and the obtained results showed that [RhIIIL2ClH2O] has mid activity compared to other SOD mimics. By analogy with the work of the original-SOD and its functional models, a mechanism for SOD-mimicking catalytic activity of the newly synthesized rhodium(III) complex has been proposed. The binding of the Rh(III) chelate to DNA was tested, and spectroscopic investigations indicated the successful binding of the metal complex to DNA by the groove/electrostatic binding pattern with intrinsic binding constants Kb of 2.76 × 106 M−1. In addition, the quercetin – based RhIII exhibits relatively higher DPPH scavenger power than the free quercetin. The in vitro data indicated the efficient anti-proliferative activities of the current rhodium(III) complex compared with cis-platin with increased safety on normal cells. In addition, our data revealed that the studied RhIII complex could prevent cancer cell replication with increasing the p53 levels, inhibit both Bcl2 and MMP9, then activating caspase 9, which then cleaves caspase 3, leading to apoptosis triggering. Apoptosis activation led to cell cycle arrest at the pre-G1 phase and decreased Hela cell proliferation, which appeared in the decreased G2/M phase. Ongoing biological assays indicate that the current Rh(III) complex is a promising anti-proliferative agent with minimal toxicity to normal cells.

Contributions to the stereochemistry of zirconium oxysalts\u2014part IV: syntheses and crystal structures of Zr2(OH)2(XO4)3\xb74H2O (X\u2009=\u2009S, Se), Zr(SO4)2\xb74H2O, and Zr(SeO3)2

Zr2(OH)2(XO4)3·4H2O (X = S, Se), Zr(SO4)2·4H2O, and Zr(SeO3)2 were synthesized at low-hydrothermal conditions from mixtures of Zr2O2(CO3)(OH)2, the respective acids, and minor amounts of water. While Zr2(OH)2(XO4)3·4H2O (X = S, Se) and Zr(SO4)2·4H2O form crystals up to several tenths of a mm, Zr(SeO3)2 was mainly obtained as microcrystalline powder, single crystals rarely exceeded 10 μm in size. Samples were investigated by single-crystal X-ray techniques and in the case of Zr(SeO3)2 also by X-ray powder diffraction. The compounds Zr2(OH)2(XO4)3·4H2O (X = S, Se) crystallize in the Ce2(OH)2(SO4)3·4H2O structure type (C2/c, Z = 4, a = 13.034(2) / 13.308(3), b = 6.500(1) / 6.683(2), c = 15.056(3) / 15.383(4) Å, β = 96.27(1) / 96.81(1)°, V = 1267.9(4) / 1358.5(6) Å3 for X = S / Se, respectively). Tetragonal aniprisms Zr[8]O8 are edge-connected to dimers that share corners with XO4 tetrahedra forming a three-dimensional network. Zr(SO4)2·4H2O (Fddd, Z = 8, a = 5.498(1), b = 11.618(3), c = 25.893(6) Å, V = 1653.9(6) Å3) is isotypic with the respective selenate compound. Occasionally, pseudomerohedral twinning is observed, simulating a larger monoclinic C-centered unit cell. Again, tetragonal antiprisms Zr[8]O8 are formed; however, they are corner-linked with SO4 tetrahedra to Zr(SO4)2 layers interconnected solely by hydrogen bonds. Zr(SeO3)2 crystallizes in P21/c, Z = 2; a = 4.9724(3), b = 8.5992(5), c = 6.9447(3) Å, β = 110.128(3)°, V = 278.81(3) Å3 (unit cell from powder data) and belongs to the β-Sn(SeO3)2 structure type established further for Ti(SeO3)2 and Pb(SeO3)2. Isolated ZrO6 octahedra share corners with the selenite groups forming a three-dimensional network.Graphical abstract

An innovative electron paramagnetic resonance and statistical analysis approach to investigate the geographical origin of multi-layered samples from a Renaissance painting

The present study aims at unravelling whether an innovative, integrated method based on electron paramagnetic resonance (EPR) spectroscopy and statistical analysis could shed light on the mineralogical attribution of calcium carbonate, CaCO3, microcrystalline powders found in an unusual preparation layer of a Renaissance painting on wood. Moreover, the undertaken investigation was performed to assess, if possible, the geographical provenance of the same carbonate powders. A specifically designed procedure was operated based on previous methods applied to the investigation of ancient white and colored marbles.Microscopic samples were taken from the painting with the aim of keeping both their size and mass at a minimum possible. All investigated samples consist of a highly complex, multi-layered, heterogeneous material, where the calcium carbonate aliquot is very limited. The investigation has been carried out in a non-destructive way, registering the EPR spectra of the fragments, identifying the diagnostic Mn(II) spectra, parameterizing them, and comparing them with the most extensive available database through a set of robust statistical methods. The main results include the attribution to calcite (marble rather than chalk), the mineralogical speciation of the carbonate layer and the reduction of the possible calcite provenance sites to few localities where marble was exploited. Among them, the marble from Apuan Alps is one of the likely provenances of this calcite.

The first characterization of cubic Nd3+-doped mixed La2MoWO9 in micro-crystalline powders and translucent micro-ceramics

Crystal structure of Nd3+-doped La2MoWO9 new optical material was investigated and translucent optical ceramics were fabricated for the first time.

New perspective materials for solar cells: Cu-=SUB=-2-=/SUB=-CrSnS-=SUB=-4-=/SUB=- solid solutions with orthorhombic structure

The Cu2CrSnS4 microcrystalline powders and films with orthorhombic structure were obtained by solid-phase synthesis, and their Raman spectra were recorded for the first time. By optical spectroscopy, it was found that their Eg=1.70 eV, while in energy band gap of the powders there is a donor level with E=1.23 eV. It is shown for the first time that films of this material are photosensitive and have p-type of dark conductivity. Keywords: solid-phase synthesis, microcrystalline powder, film, dark conductivity.

Efficient near-infrared quantum cutting by cooperative energy transfer in Bi3TeBO9:Nd3+ phosphors

An efficient near-infrared quantum cutting process by cooperative down-conversion of active Bi3+ and Nd3+ ions was demonstrated in Bi3TeBO9:Nd3+ phosphors. In particular, the near-infrared emission of Nd3+ ions enhanced by Bi3+ ions of a series of novel Bi3TeBO9:Nd3+ microcrystalline powders doped with Nd3+ ions in various concentrations was investigated. In order to investigate the luminescent properties of BTBO:Nd3+ powders, the excitation and emission spectra and the fluorescence decay time were measured and analyzed. In particular, the emission of Bi3TeBO9:Nd3+ at 890 and 1064 nm was excited at 327 nm (via energy transfer from Bi3+ ions) and at 586.4 nm (directly by Nd3+ ions). The highest intensity emission bands in near-infrared were detected in the spectra of Bi3TeBO9:Nd3+ doped with 5.0 and 0.5 at.% of Nd3+ ions upon excitation in ultraviolet and visible spectral range, respectively. The fluorescence decay lifetime monitored at 1064 nm for Bi3TeBO9:Nd3+ powders shows the single- or double-exponential character depending on the concentrations of Nd3+ ions. The possible mechanisms of energy relaxation after excitation Bi3TeBO9:Nd3+ powders in ultraviolet or visible spectral range were discussed. The investigated Bi3TeBO9:Nd3+ phosphors efficiently concentrate the ultraviolet/visible radiation in the near-infrared spectral range and can be potentially used as effective spectral converters.Graphical abstract

Исследование кристаллической структуры, оптических и электрофизических свойств нового полупроводникового материала Cu-=SUB=-2-=/SUB=-CrSnS-=SUB=-4-=/SUB=- для тонкопленочных солнечных элементов

The Cu2CrSnS4 microcrystalline powders and films with orthorhombic structure were obtained by solid-phase synthesis, and their Raman spectra were recorded for the first time. By optical spectroscopy, it was found that their Eg = 1.70 eV, while in energy band gap of the powders there is a donor level with E = 1.23 eV. It is shown for the first time that films of this material are photosensitive and have p-type of dark conductivity.

Luminescence and energy transfer processes in LuNbO4:Bi, Eu

Microcrystalline powders of LuNbO4:Bi3+, Eu3+ with the same nominal Bi3+ concentration (2 at.%) and different nominal Eu3+ concentrations (varying from 0 to 8 at.%) are synthesized and analyzed by the X-ray diffraction method. Photoluminescence characteristics of the co-doped LuNbO4:Bi, Eu powders are investigated by the steady-state and time-resolved luminescence spectroscopy methods in a wide temperature range (4.2–500 K) and compared with those of the undoped and bismuth-doped LuNbO4. It is found that owing to the overlap of the intrinsic and Bi3+-related emission bands with the absorption bands of Eu3+, an effective non-radiative (resonance) energy transfer from both the host and the Bi3+-related exciton-like states to Eu3+ ions, resulting in the appearance of the luminescence in the 1.6–3.8 eV energy range, takes place in LuNbO4:Bi, Eu. The exchange interaction is found to be responsible for the energy transfer process. The possible application of LuNbO4:Bi, Eu in white light-emitting diodes is discussed.

Study of the structure and optoelectronic properties of Cu2Ge(SexS1-x)3 microcrystalline powders

In this study, the Cu2Ge(SexS1-x)3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) microcrystalline powders were synthesized from elemental precursors in the liquid phase of lithium iodide (LiI) flux material in evacuated quartz ampoules. The crystal structure and lattice parameters of the Cu2Ge(SexS1-x)3 (CGSSe) were determined by X-ray diffraction measurement. Results showed the crystal structure of CGSSe transfers from monoclinic to orthorhombic with increasing the Se content in the powders, which occurs between 0.2 < x < 0.4. Raman spectroscopy showed that all sulfide related peaks in the solid solutions tend to shift toward smaller wavenumbers and the relative intensity of these peaks was decreasing and selenide related peaks shifted toward higher wavenumbers and decreased. Radiative recombination processes in CGSSe microcrystalline powders were studied by using photoluminescence spectroscopy (PL). All spectra of CGSSe were composed of two asymmetric PL peaks. Peak positions of these bands (#1 and #2) as a function of Se/S concentration show nearly linear dependence with a slope about -0.8 eV. Almost the same slope was detected for band gap values (Eg) determined from room temperature external quantum efficiency measurements. Therefore, the peak position shift with x is related to Eg shift for both PL peaks. Both peaks are related to donor-acceptor pair recombination.A best performing solar cell was fabricated by using Cu2Ge(SexS1-x)3x = 0.6 powder crystals as absorber material, exhibiting an open-circuit voltage of 537 mV, current density of 15.8 mA/cm2, fill factor of 37.2% and a conversion efficiency of 3.16%.

Single crystal monolithic upconverter solar cell device tandems with integrated optics

Solar photons possessing energy less than the bandgap of a single-junction solar cell can be utilized via the upconversion (UC) of two or more photons, resulting in the emission of a single above-bandgap photon. Due to the non-linear nature of UC, highly concentrated light is required, which is typically much greater than the practical concentration limits of a solar cell. It has been proposed that concentrating upconversion solar cells (UC-SC) with optical elements integrated into the device could help realize the high solar irradiance required. To avoid scattering problems arising from common UC materials based on micro-crystalline powders, in this work, concentrators are investigated with mono-crystalline upconverters in silicon-based tandem devices. An external quantum efficiency (EQE) of 6% with 1493 nm infrared illumination at 876 W / m 2 was obtained in upconverter device with concave integrated optics. At an irradiance higher than 90 W / m 2 (equivalent to 2.95 × in the 1450–1600 nm range), the non-concentrating UC-SC exhibited 1 . 5 × higher EQE than the UC-SC with a compound parabolic concentrator (CPC), while below 90 W / m 2 the CPC UC-SC exhibited 1.95 × higher EQE than the non-concentrating reference device. Due to the negligible scattering of the UC layer, the distribution of localized irradiance is revealed along with its effect on the performance of devices. It is found that irradiance is accumulated within the first 1 mm of the UC layer with peaks at variable depths according to the concentrating scheme. These results suggest ample space for improved UC devices by using integrated optics.

Synthesis and Characterization of Mixed Ligand Complexes of Copper(II) with Adenine and Dicarboxylic Acids

Three mixed ligand complexes of copper(II) with adenine and dicarboxylic acids have been synthesized. The resulting complexes were characterized by their melting point, solubility, metal content analysis, FT-IR and UV-visible spectroscopy, magnetic measurement, thermal analysis, cyclic voltammetric measurement and X-ray powder diffraction study. The products are microcrystalline powder, slightly soluble in water and decompose at high temperature. Under experimental condition, the ligands adenine (Ade) behaves as a neutral ligand, whereas oxalic acid (OxH2), succinic acid (SucH2) and tartaric acid (TarH2) are doubly deprotonated to form dianionic ligands that are coordinated to the Cu(II) ion. The Cu(II) content analysis of the complexes confine to their stoichiometry [Cu(Ade)(L)(H2O)] (L = Ox, Suc, or Tar dianion). Electrochemical redox behavior of the complexes in their reaction medium was also examined. They exhibit quasi-reversible one-electron transfer processes. Dhaka Univ. J. Sci. 69(2): 76-81, 2021 (July)

Synthesis and X-ray-graphical characteristics of the MеSn&lt;sub&gt;2&lt;/sub&gt;F&lt;sub&gt;5&lt;/sub&gt; (Mе = Na, K, Rb, Cs) fluoride-ion conductors

Objectives. Pentafluorodistannates of alkali metals are promising materials for use as electrolytes in fluoride-ion batteries due to their electrophysical properties, such as high fluoride-ion conductivity. This work aims to synthesize crystals of alkali metals MeSn2F5 (Me = Na, K, Rb, Cs), carry out X-ray diffraction studies on them, and investigate the possibility of obtaining lithium fluorostannates.Methods. Supersaturated aqueous solutions were employed to synthesize the crystals. The X-ray diffraction (XRD) analysis was carried out.Results. Oversaturated solutions yield microcrystalline powders of sodium, potassium, rubidium, and cesium pentafluorodistannates. The presence of a single-phase was confirmed by XRD analysis of the powders corresponding to the MеSn2F5 (Mе = Na, K, Rb, Cs) composition. XRD data analysis and literature indicated that MеSn2F5 (Mе = K, Rb, Cs) have a fluorite-like structure, with the cations forming three-layer closest packing. The RbSn2F5 compound was discovered to be isostructural to KSn2F5. Based on this discovery, RbSn2F5 was reindexed to a hexagonal unit cell with parameters a = 7.40(3) Å, с = 10.12(6) Å (KSn2F5 P3, a = 7.29(3) Å, с = 9.86(2) Å). The CsSn2F5 compound was reindexed to a monoclinic unit cell (a = 10.03(4) Å, b = 5.92(7) Å, c = 11.96(9) Å, β = 107.4(5)°). A crystallochemical analysis of the pentafluorodistannates was carried out, and common structural motifs were discovered. The motifs are similar to lead tetrafluorostannate PbSnF4, the best fluoride-ion conductor. The effect of the pentafluorodistannates structures on the ionic conductivity is considered. The LiF–SnF2 system contains no compounds; the compositions were obtained by melting the original fluorides. Conclusions. MеSn2F5 (Mе = Na, K, Rb, Cs) were synthesized and investigated by XRD analysis. The structural characteristics of the RbSn2F5 and CsSn2F5 compounds have been redefined. The crystallochemical structure is analyzed in relation to the electrophysical properties of the alkali metal pentafluorodistannates. Pentafluorodistannates MеSn2F5 (Mе = K, Rb, Cs) have a fluorite-like structural motif with cubic parameters а = 5.694 Å (KSn2F5), а = 5.846 Å (RbSn2F5), а = 6.100 Å (CsSn2F5), with the cations forming three-layer closest packing. The cationic layers alternate like Me–Sn–Sn–Me (Mе = K, Rb, Cs). For KSn2F5 and RbSn2F5, they are normal to the three-fold axis and normal to the four-fold axis in the case of CsSn2F5.

Metal-Organic Framework superstructures with long-ranged orientational order via E-field assisted liquid crystal assembly

Most MOFs are non-cubic, with functionality dependent upon crystallographic direction, and are largely prepared as microcrystalline powders. Therefore, general methods to orient and assemble free-standing MOF crystals are especially important and urgently needed. This is addressed here through the novel strategy of E-field assisted liquid crystal assembly, applied to MIL-53-NH2(Al), MIL-68(In) and NU-1000 MOF crystals, with aspect ratios ranging from 10 to 1.2, to form highly oriented MOF superstructures which were photopolymerized to fix their long-ranged order. This new strategy for controlling MOF orientation and packing side-steps the traditional requirements of particle monodispersity, shape homogeneity and high aspect ratios (>4.7) typical of colloidal and liquid crystal assembly, and is applicable even to polydispersed MOF crystals, thereby paving the way towards the development of highly oriented MOF composites with improved functionality.

Multi-Length Scale Structure of 2D/3D Dion-Jacobson Hybrid Perovskites Based on an Aromatic Diammonium Spacer.

Dion-Jacobson (DJ) iodoplumbates based on 1,4-phenylenedimethanammonium (PDMA) have recently emerged as promising light absorbers for perovskite solar cells. While PDMA is one of the simplest aromatic spacers potentially capable of forming a DJ structure based on (PDMA)An-1 Pbn I3n+1 composition, the crystallographic proof has not been reported so far. Single crystal structure of a DJ phase based on PDMA is presented and high-field solid-state NMR spectroscopy is used to characterize the structure of PDMA-based iodoplumbates prepared as thin films and bulk microcrystalline powders. It is shown that their atomic-level structure does not depend on the method of synthesis and that it is ordered and similar for all iodoplumbate homologues. Moreover, the presence of lower (n) homologues in thin films is identified through UV-Vis spectroscopy, photoluminescence spectroscopy, and X-ray diffraction measurements, complemented by cathodoluminescence mapping. A closer look using cathodoluminescence shows that the micron-scale microstructure corresponds to a mixture of different layered homologues that are well distributed throughout the film and the presence of layer edge states which dominate the emission. This work therefore determines the formation of DJ phases based on PDMA as the spacer cation and reveals their properties on a multi-length scale, which is relevant for their application in optoelectronics.

Sodium rare earth metal amides Na3 RE(NH2)6 (RE = La–Nd, Er, Yb) from ammonothermal synthesis

Abstract The amides Na3 RE(NH2)6 have been obtained from the metals in supercritical ammonia under ammonobasic conditions at 573 K and 70 MPa for RE = La–Nd, and at 473 K and 40 MPa for RE = Er, Yb. All compounds are formed in the hot zone within a temperature gradient, indicating a retrograde solubility under the applied process conditions. These amides represent soluble intermediates in ammonothermal binary rare earth metal nitride synthesis. All compounds were obtained as microcrystalline powders, while single crystals of those amides containing the heavier rare earth metals could be isolated. The crystal structures were solved and refined from single-crystal and powder X-ray diffraction intensity data. The results of vibrational spectroscopy are reported. Thermal analysis measurements under inert gas atmosphere demonstrated a decomposition to the respective black binary rare earth metal nitrides REN1−δ .

Facile synthesis of Zr-based metal-organic gel (Zr-MOG) using “green” sol-gel approach

Zirconium-based metal–organic gels (Zr-MOG) was introduced to overcome the drawbacks such as macro-shaping and poor hydrostability of as-synthesized metal–organic frameworks in microcrystalline powder in industrial applications. Zirconium nitrate oxyhydrate and dicarboxylic acid were initially used as organic ligands to form a soft supramolecular structure in a sol–gel like processing method. Amorphous Zr-MOG were successfully synthesized without chloride ion and toxic modulators for the first time in an attempt to a sustainable and green approach. The estimated as well as observed pore size was at ca. 5 nm with a disordered wormhole-like structure analogous to mesoporous silica materials. The agitation method, aging duration and temperature were highly dependent factors for the formation of amorphous Zr-MOG xerogel in the absence of chloride ions and toxic organic solvents. The evidences suggested that simple and quick washing with ethanol of the obtained gel with aging in between as the key factor to successful formation at room temperature analogous to that of siliceous inorganic materials. X-ray photoelectron spectroscopy (XPS) spectra indicated that the Zr atoms and organic linker bonding were intact, forming an amorphous metal–organic gel network. The deconvolution of O1s spectra resulted in three peaks at 531.9 eV, 530 eV and 529 eV attributable to Zr-O-C, Zr-O-Zr and Zr-O bonds energy, respectively. The presence of Zr-O-C peak suggested successful formation of metal and organic moieties in Zr-MOG. In addition, the amorphous gel network was intact as evidenced in the presence of Zr-O-C peak in as-synthesized, dried gel.