Shape Of Rhombic Dodecahedron Research Articles

Dynamic Stereochemistry of M8 Pd6 Supramolecular Cages Based on Metal-Center Lability for Differential Chiral Induction, Resolution, and Recognition.

A series of isostructural supramolecular cages with a rhombic dodecahedron shape have been assembled with distinct metal-coordination lability (M8 Pd6 -MOC-16, M=Ru2+ , Fe2+ , Ni2+ , Zn2+ ). The chirality transfer between metal centers generally imposes homochirality on individual cages to enable solvent-dependent spontaneous resolution of Δ8 /Λ8 -M8 Pd6 enantiomers; however, their distinguishable stereochemical dynamics manifests differential chiral phenomena governed by the cage stability following the order Ru8 Pd6 >Ni8 Pd6 >Fe8 Pd6 >Zn8 Pd6 . The highly labile Zn centers endow the Zn8 Pd6 cage with conformational flexibility and deformation, enabling intrigue chiral-Δ8 /Λ8 -Zn8 Pd6 to meso-Δ4 Λ4 -Zn8 Pd6 transition induced by anions. The cage stabilization effect differs from inert Ru2+ , metastable Fe2+ /Ni2+ , and labile Zn2+ , resulting in different chiral-guest induction. Strikingly, solvent-mediated host-guest interactions have been revealed for Δ8 /Λ8 -(Ru/Ni/Fe)8 Pd6 cages to discriminate the chiral recognition of the guests with opposite chirality. These results demonstrate a versatile procedure to control the stereochemistry of metal-organic cages based on the dynamic metal centers, thus providing guidance to maneuver cage chirality at a supramolecular level by virtue of the solvent, anion, and guest to benefit practical applications.

Dynamic Stereochemistry of M8Pd6 Supramolecular Cages Based on Metal‐Center Lability for Differential Chiral Induction, Resolution, and Recognition

AbstractA series of isostructural supramolecular cages with a rhombic dodecahedron shape have been assembled with distinct metal‐coordination lability (M8Pd6‐MOC‐16, M=Ru2+, Fe2+, Ni2+, Zn2+). The chirality transfer between metal centers generally imposes homochirality on individual cages to enable solvent‐dependent spontaneous resolution of Δ8/Λ8−M8Pd6 enantiomers; however, their distinguishable stereochemical dynamics manifests differential chiral phenomena governed by the cage stability following the order Ru8Pd6>Ni8Pd6>Fe8Pd6>Zn8Pd6. The highly labile Zn centers endow the Zn8Pd6 cage with conformational flexibility and deformation, enabling intrigue chiral‐Δ8/Λ8−Zn8Pd6 to meso‐Δ4Λ4−Zn8Pd6 transition induced by anions. The cage stabilization effect differs from inert Ru2+, metastable Fe2+/Ni2+, and labile Zn2+, resulting in different chiral‐guest induction. Strikingly, solvent‐mediated host–guest interactions have been revealed for Δ8/Λ8−(Ru/Ni/Fe)8Pd6 cages to discriminate the chiral recognition of the guests with opposite chirality. These results demonstrate a versatile procedure to control the stereochemistry of metal‐organic cages based on the dynamic metal centers, thus providing guidance to maneuver cage chirality at a supramolecular level by virtue of the solvent, anion, and guest to benefit practical applications.

Utilization of APTES-functionalized coconut waste-based cellulose microfiber/zeolitic-imidazolate framework-8 composite for curcumin delivery

With more than 7 million tons of coconut husk generated annually, this study proposes to fabricate the composite of coconut waste-based cellulose microfibers and zeolitic imidazolate framework-8 functionalized with (3-aminopropyl)-triethoxysilane (APTES-CMF/ZIF-8), which is used for curcumin uptake/release. The surface area and pore volume of APTES-CMF/ZIF-8 are found, respectively, at 247.6 m2/g and 0.21 m3/g. The morphology study also shows that the waste-based CMF possesses a uniform width at 5–10 μm, and a length of up to several tens of microns, while the impregnated ZIF-8 has a rhombic dodecahedron shape with a particle diameter of 300–400 nm. The behavior of the curcumin uptake using APTES-CMF/ZIF-8 is elucidated via kinetics, isotherm, and thermodynamic studies. The maximum curcumin adsorption reaches 626.4 mg/g at the following condition: APTES-CMF/ZIF-8 loading (mc) = 0.1% (w/w), uptake duration (t) = 1440 min, temperature (T) = 30 °C, and initial curcumin concentration of 1000 mg/L. This uptake follows the pseudo-second-order law and monolayer mechanism, with the fast migration of curcumin from the bulk solution to the surface of APTES-CMF/ZIF-8 as the rate-governing step. The curcumin and APTES-CMF/ZIF-8 interaction is driven by the electron exchange between both molecules. The release study of curcumin from Cur@APTES-CMF/ZIF-8 complies with the slow-first-order model. Moreover, the cumulative release is monitored at 74.2% at pH 5.5 and 47.9% at pH 7.4, signifying the pH-responsiveness of APTES-CMF/ZIF-8.

Construction of Co3O4 nanopolyhedra with rich oxygen vacancies from ZIF-67 for efficient photocatalytic nitrogen fixation.

Photocatalytic nitrogen fixation has attracted much attention due to the fact that it is a way of using solar energy to achieve clean and sustainable conversion of nitrogen to ammonia under mild conditions. In this paper, different proportions of Zn-doped Co3O4 nanopolyhedrons were synthesized using bimetallic ZIFs containing Co2+ and Zn2+ as precursors for the construction of photocatalytic nitrogen fixation semiconductor materials for the first time. The synthesized Co3O4 nano-polyhedron still retains the rhombic dodecahedron shape of ZIF-67 and exhibits a large specific surface area. Moreover, Zn doping results in abundant oxygen vacancies on the surface of Co3O4 polyhedron. These oxygen vacancies not only provide active sites for nitrogen adsorption and activation, but also enhance the separation ability of photocarriers, which can significantly improve the efficiency of photocatalytic nitrogen fixation of the material. When Zn-Co3O4-30 is utilized as the catalyst for photocatalytic nitrogen fixation, the nitrogen fixation rate is 96.8μmolg-1h-1, which is much higher than that of pure-Co3O4. In this study, heteroatom-doped Co3O4 polyhedron with rich oxygen vacancy was synthesized by low-temperature oxidation method, which provides a new idea for the design and synthesis of skeleton-based photocatalytic nitrogen fixation materials.

Metal-Organic Framework-Derived Trimetallic Nanocomposites as Efficient Bifunctional Oxygen Catalysts for Zinc-Air Batteries.

Transition-metal-based multifunctional catalysts have attracted increasing attention owing to high possibilities of substituting the expensive noble-metal-based catalysts in various scenarios. Multivariate metal-organic frameworks (MTV-MOFs) are ideal precursors to prepare multimetallic nanocomposites with high catalytic activity since the uniform distribution and precise regulation of mixed metal centers, as well as the consequent strong synergistic effect, could be readily achieved. Herein, a Mn/Co/Ni trimetallic catalyst (MnCoNi-C-D) with a hollow rhombic dodecahedron shape was synthesized via pyrolysis of the corresponding trimetallic-based MTV-MOF. The catalyst shows outstanding electrochemical activity toward the oxygen reduction reaction including a half-wave potential of 0.82 V and superior tolerance against methanol as well as high stability in an alkaline medium, and its oxygen evolution reaction activity also surpasses a RuO2 catalyst. Moreover, primary and rechargeable zinc-air batteries based on MnCoNi-C-D delivered preferable performances compared with commercial Pt/C-RuO2, including higher peak power density (116.4 mW cm-2), higher specific capacity (841.3 mAh g-1), higher open-circuit potential (OCV) (1.46 V), and better stability for more than 180 h. A comprehensive comparison was also conducted to prove the necessity of employing the MTV-MOF as the precursor and investigate the intrinsic superiority of the catalyst.

Hydrogen production and photocatalytic activity of g‐C3N4/Co‐MOF (ZIF‐67) nanocomposite under visible light irradiation

Herein, cobalt (Co)‐based metal–organic zeolitic imidazole frameworks (ZIF‐67) coupled with g‐C3N4 nanosheets synthesized via a simple microwave irradiation method. SEM, TEM and HR‐TEM results showed that ZIF‐67 were uniformly dispersed on g‐C3N4 surfaces and had a rhombic dodecahedron shape. The photocatalytic properties of g‐C3N4/ZIF‐67 nanocomposite were evaluated by photocatalytic dye degradation of crystal violet (CV), 4‐chlorophenol (4‐CP) and photocatalytic hydrogen (H2) production. In presence of visible light illumination, the photocatalytic dye results showed that 95% CV degradation and 53% 4‐CP degradation within 80 min. The H2 production of the g‐C3N4/ZIF‐67 composite was 2084 μmol g−1, which is 3.84 folds greater than that of bare g‐C3N4 (541 μmol g−1).

(Invited) Playing Around with Shape and Composition of Nanoparticles As Catalysts for Ethanol Oxidation

Nowadays, nanoparticles (NPs) with sizes between 2 to 50 nm become more and more popular, because they can be applied in various fields such as materials science, chemistry, catalysis, medicine or biology. Until now, noble metal NPs were used as I generation catalysts, as they exhibit good electrocatalytic activity towards ethanol oxidation reaction (EOR) [1]. The best EOR performance, however, was observed for ternary catalysts consisting of PtRh nanoalloy NPs supported by SnO2 NPs, designed and synthesized in Adzic’s group, [2-5]. Indeed, the break of the C=C bond in the ethanol molecule occurs at the interface between PtRh and SnO2 particles. Therefore their physical contact is imperative for the effectiveness of the catalyst. The aim of reducing the expensive noble metal content in the catalyst has lead to the design the II generation of catalysts having a core/shell structure, where only the shell consists of Pt and the core comprises a cheaper metal. Nanoparticles with fancy shapes can be considered as the III generation catalysts. In particular, hollow metallic nanoparticles become attractive as fuel cells catalysts, since they make use of the large surface area they offer [6-8]. These three-dimensional (3D) structures, such as nanoframes, nanoboxes or nanocages can be fabricated either by etching away a certain volume of the solid nanoparticles (NPs) or by galvanic replacement reactions (GRR), transforming solid metal NPs into multimetallic hollow NPs [8]. During the GRR, the template material is oxidized and dissolved, while metal ions are reduced and the resultant atoms are deposited on the surface of the template. The driving force of the GRR is the difference in redox potential between the two metals. The present study is focused on several types of catalytic nanoparticles (NPs) studied using TEM techniques combined with energy-dispersive X-ray spectroscopy (EDX). Tomographic reconstruction was applied to confirm the 3D structure of the NPs. In the ternary PtRh/SnO2 nanocatalysts, the role of Rh is to cleave the C-C bond of ethanol, while SnO2 provides OH species to oxidize intermediates and to free Pt and Rh sites for further ethanol oxidation [2]. Because rhodium is not available in Poland it was aimed to be replaced by Re. Pt/Re/SnO2 NPs were synthesized individually by colloidal and polyol methods and interconnected in a controlled way. For that purpose zeta potentials of the respective NPs were measured as a function of the solution pH. Subsequently NPs with opposite zeta potentials were mixed to obtain binary and ternary combinations. Three-dimensional (3D) catalysts having a rhombic dodecahedron shape, composed of a Pt frame surrounding a Ni core, which was subsequently removed by etching or GRR with tin were investigated. The morphology of these 3D PtNi particles strongly depends on the synthesis parameters allowing fabricating dodecahedrons, core-shell or even dendritic structures. A number of GRR between Ni and Sn was performed in order to track the reaction over time. The impact of the concentration of tin ions on the obtained nanoframes was investigated and the Pt:Ni:Sn atomic ratio at different reaction stages was determined. References Antolini, E. Catalysts for direct ethanol fuel cells. J. Power Sources 170 (2007) 1.Kowal et all, Nature Materials 9 (2009) 325.Adzic, A. Kowal, (Brookhaven National Laboratory), Patent Application Publication, Pub. No. US2009/0068505 A1 (2009).Li et all, Electrochimica Acta 55 (2010) 4331.Kowal et all, Electrochem. Comm. 11 (2009) 724.Chen et all, Science 343 (2014) 1339.Ruditskiy and Y. Xia, ACS Nano 11 (2017) 23.Hajfathalian et al., ACS Nano 10 (2016) 6354. Acknowledgements The authors thank the Institute of Engineering Materials and Biomaterials of the Silesian University of Technology and the Department of Chemistry, University of Warsaw for the use of the Titan FEI TEM and the Talos F200 FEI TEM instruments, respectively. Financial support from the Polish National Science Centre (NCN), grant UMO-2014/13/B/ST5/04497 is acknowledged. Partial financial support by Pik-Instruments is greatly acknowledged. Figure 1

Design, synthesis and characterization of MOF-199 and ZIF-8: Applications in the adsorption of phenols derivatives in aqueous solution

In this work, the adsorption characteristics of metal-organic frameworks (MOFs: MOF-199 and ZIF-8) with two different types of structure were analyzed. MOF-199 consists of copper-based metal clusters while the ZIF-8 consists of organic molecules interlaced with zinc atoms and these have octahedral morphology and typical rhombic dodecahedron shape, respectively. The results of phenol (Ph) and p -nitro phenol (PNP) adsorption capacity from aqueous solution show that MOF-199 has a higher adsorption capacity: Ph 79.55% and PNP 89.3%, while for ZIF-8 the adsorption capacity was Ph 65.5% and PNP 77.0%. Adsorption of phenols was fit to Langmuir, Sips and Redlich-Peterson models and kinetics by pseudo-second order. Gibbs free energy (ΔG°) shows that adsorption processes studied are spontaneous.

Morphology-controlled fabrication of Ag3PO4/chitosan nanocomposites with enhanced visible-light photocatalytic performance using different molecular weight chitosan

A series of Ag3PO4 and chitosan (CS) nanocomposites (Ag3PO4/CS) were prepared through in situ growth of Ag3PO4 with different molecular weight chitosan as adsorbent and soft-template. The structure and properties of as-prepared Ag3PO4/CS nanocomposites were characterized by XRD, FT-IR, FESEM, TEM, XPS, BET and UV–vis/DRS. The visible-light photocatalytic decolorization behavior of Ag3PO4/CS nanocomposites was investigated using methyl orange as a model pollutant. It was found that the morphology and photocatalytic decolorization activity of the nanocomposites significantly depended on the molecular weight of chitosan. The decolorization of methyl orange was ascribed to the synergistic effect of photocatalysis and adsorption. When Ag3PO4/CS nanocomposites were prepared in the presence of high molecular weight chitosan, Ag3PO4 particles with cubic or rhombic dodecahedron shape and about 200 to 550nm in diameter were wrapped in chitosan. Meanwhile, when Ag3PO4/CS nanocomposites were fabricated using low molecular weight chitosan as soft-template, 150–400nm flower-like spheres were obtained which were aggregated by a large number of nanoscale Ag3PO4 crystalline grains and connected by chitosan matrix. The special morphology of Ag3PO4/CS nanocomposites greatly increased the active surface area and the photocatalytic performance. The results in this study suggested that semiconductor photocatalysts with novel morphology and enhanced photocatalytic ability could be fabricated by using different molecular weight chitosan as soft-template.

Mechanical behavior of open-cell rhombic dodecahedron Ti–6Al–4V lattice structure

The compression behavior of Ti–6Al–4V lattice structure with a cell shape of rhombic dodecahedron, which was fabricated by electron beam melting, was investigated at different temperatures. A series of quasi-static compression tests were performed at ambient temperature, 200°C, 400°C and 600°C with a strain rate of 10−3s−1. Two groups of design configurations were adopted by changing the cell size and thickness of struts with the sample size maintained unchanged. The results revealed that their properties varied with different cell sizes and temperatures. Larger cell size leaded to lower modulus and strength of the lattice. Higher temperatures resulted in lower strengths, modulus, densification strains and plateau stresses. The energy absorption of lattice at high temperature was discussed, and the experimental data were compared with aluminum foams, titanium foams and stainless steel lattice. It demonstrated that the rhombic dodecahedron Ti–6Al–4V lattice structure could be applied as load-bearing components and energy absorber at high temperature.

Synthesis of Rhombic Dodecahedral Gold Nanocrystals by Dimethylformamide Reduction

We report a facile and low-cost wet chemical method for preparation of gold (Au) nanocrystals with morphology of well-defined rhombic dodecahedron (RD). The Au nanocrystals with the RD shape have been synthesized by reducing HAuCl4 in N,N-dimethylformamide (DMF) solvent in an autoclave for 15-24 h at 90 degrees C. Thus-synthesized Au nanocrystals have been characterized by a scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). The results show that the RD nanocrystals are exclusively enclosed by twelve {110}-type facets. Furthermore, concave RD Au nanocrystals can also be produced only by changing reaction time or adding ascorbic acid (AA). A possible evolution mechanism of the RD Au nanocrystals has been suggested.

Preparation and photophysical properties of rhombic dodecahedral perovskite-type BaSnO3

BaSnO3 grains with a rhombic dodecahedron shape have been synthesized via a facile modified hydrothermal approach. The structure and morphology evolution during hydrothermal treatment have been investigated with X-ray diffraction, scanning electron microscopy, and Raman and Fourier transform infrared spectroscopy. The sample with the single-phase of BaSnO3 can be obtained at the hydrothermal temperature of 24 °C, and the grain size grows with an increasing temperature from 10 to 15 μm below 270 °C. But the grain size decreases sharply to 4 μm when the temperature reaches 280 °C. The optical absorption and surface photovoltage spectroscopy analysis indicate that controlling the size and shape is of great importance in tuning photophysical properties of BaSnO3 powders.

Structural transition in rare earth oxide clusters

Size effects, such as structure transition, have been reported in small clusters of alkali halide compounds. We extend the study to rare earth sesquioxide (Gd(2)O(3)) clusters which are as ionic as the alkali halide compounds, but have a more complicated structure. In a clean and controlled environment (ultra high vacuum), such particles are well crystallized, facetted and tend to adopt a rhombic dodecahedron shape. This indicates the major role of highly ionic bonds in preserving the crystal lattice even at small sizes (a few lattice parameter). Based on both cathodo-luminescence and transmission electron microscopy, we report the existence of a structural transition from bcc to monoclinic at small sizes.

Rhombic Cell Analysis – A New Way of Probing the Large-Scale Structure of the Universe. I. General Considerations

A new way of probing the large-scale structure of the universe is proposed. Space is partitioned into cells the shape of rhombic dodecahedron. The cells are labelled ``filled'' or ``empty'' according as they contain galaxies or not. The cell size is so chosen as to have nearly equal numbers of filled and empty cells for the given galaxy sample. Two observables on each cell are definable: the number of its {\em like} neighbors, $n_1$, and a two-suffixed topological type $\tau$, the suffixes being the numbers of its like and unlike {\em neighbor-groups}. The frequency distributions of $n_1$ and $\tau$ in the observed set of filled (empty) cells are then considered as indicators of the morphology of the set. The method is applied to the CfA catalogue of galaxies as an illustration. Despite its limited size the data offers evidence 1) that the empty cells are more strongly clustered than the filled cells, and 2) that the filled cells, but not the empty cells, have a tendency of occurring in sheets. Further directions of development both in theory and application are indicated.