Primary Building Units Research Articles

Effect of sodium borohydride on growth process of controlled flower-like nanostructured Cu 2O/CuO films and their hydrophobic property

In this paper, we report on the three-dimensional nanostructured Cu 2O/CuO films with controlled flower-like shapes using a direct crystallization approach in the presence of sodium borohydride without using any performed template, surfactant or oxidant. The microstructures and shapes of Cu 2O/CuO architectures were investigated by field emission scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Three types of chrysanthemum-like, candock-like and dandelion-like CuO microstructures consisting of densely packed building blocks of nanobelts or nanoribbons were achieved by governing the concentrations of NaBH 4. Possible growth mechanisms for the controlled organization of primary building units into three-dimensional flower-like architectures were proposed. After simple surface modification with sodium laurate, the resulting films displayed hydrophobic and even superhydrophobic properties owing to their special surface nano-/microstructures.

Spectroscopic Study of the Effects of Pressure Media on High-Pressure Phase Transitions in Natrolite

Structural phase transitions in natrolite have been investigated as a function of pressure and different hydrostatic media using micro-Raman scattering and synchrotron infrared (IR) spectroscopy. Natrolite undergoes two reversible phase transitions at 0.86 and 1.53 GPa under pure water pressure medium. These phase transitions are characterized by the changes in the vibrational frequencies of four- and eight-membered rings related to the variations in the bridging T-O-T angles and the geometry of the elliptical eight-ring channels under pressure. Concomitant to the changes in the framework vibrational modes, the number of the O-H stretching vibrational modes of natrolite changes as a result of the rearrangements of the hydrogen bonds in the channels caused by a successive increase in the hydration level under hydrostatic pressure. Similar phase transitions were also observed at relatively higher pressures (1.13 and 1.59 GPa) under alcohol-water pressure medium. Furthermore, no phase transition was found up to 2.52 GPa if a lower volume ratio of the alcohol-water to natrolite was employed. This indicates that the water content in the pressure media plays a crucial role in triggering the pressure-induced phase transitions in natrolite. In addition, the average of the mode Grueneisen parameters is calculated to be about 0.6, whilemore » the thermodynamic Grueneisen parameter is found to be 1.33. This might be attributed to the contrast in the rigidity between the TO{sub 4} tetrahedral primary building units and other flexible secondary building units in the natrolite framework upon compression and subsequent water insertion.« less

Controlled synthesis of various hierarchical nanostructures of copper sulfide by a facile microwave irradiation method

Hierarchical flower-like spheres and self-assembled chains of copper sulfide have been synthesized by a facile microwave irradiation. The as-obtained products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy. The SEM and TEM results showed that three-dimensional (3D) flower-like CuS spheres are constructed by a number of two-dimensional (2D) nanosheets as primary building units, whereas the one-dimensional (1D) hierarchical chains are formed by the oriented attachment of the 3D flower-like spheres of CuS. The influences of the additive EDTA, concentration of reactants, microwave power, and reaction time on final morphology and assembled structure of the products were systematically investigated. On the basis of our experimental results, a phenomenological elucidation of the mechanism for the growth of the CuS architectures has been presented, and the driving force for the self-assembly of the nanoplates can be attributed to interfacial tension and the interaction between the hydrophilic surfaces of CuS nanoplates. EDTA acts as both a chelating reagent and a surface capping agent in the synthesis process. Moreover, the optical property of the flower-like CuS microspheres was measured by UV–vis absorption spectroscopy.

Synthesis, characterization and crystallization mechanism of SAPOs from natural kaolinite

Calcined natural kaolinite (i.e. metakaolin) was used as a combinational Si and Al source to synthesize SAPO-5, -11, -20, -34, -44, and -47. The reactivity of metakaolin with related chemicals was studied, and the solid structural evolution process of SAPO-34 was exemplified to show the crystallization mechanism of SAPOs from kaolinite. The results indicated that the products had excellent crystallinity. The Si and/or Al of metakaolin had good coordination capability with related ligands. The crystallization process of SAPO-34 from kaolinite is summarized as three stages. In the first stage of calcination (at 1073 K), kaolinite is destructured and activated. In the second stage of aging and initial heating, the surface of metakaolin is gelated and the coordinated units are stripped down to transform into the primary building units (PBUs) with increasing temperature. At a desirable temperature, the PBUs stack to form the nuclei. In the final step, crystallization is triggered when the mixture is heated up to 423 K. NMR results illustrated that Si directly participated in the crystallization of SAPO-34 mainly as Si monomer state. Formation of SAPO-34 from kaolinite, as well as other SAPOs, is believed to proceed following an activation–gelation–crystallization mechanism.

Review. Synthesis of Inorganic-Organic Hybrid Thiometallate Materials with a Special Focus on Thioantimonates and Thiostannates and in situ X-Ray Scattering Studies of their Formation

A rich variety of inorganic-organic hybrid thioantimonates and thiostannates were prepared during the last few years under solvothermal conditions applying organic amine molecules or transition metal complexes as structure directors. In this review synthetic approaches to and structural features of these thiometallates are discussed. For thioantimonates(III) the structures range from well isolated thioanions to three-dimensional networks, whereas the structural chemistry of thiostannates(IV) is strongly dominated by the [Sn2S6]4− anion, and no three-dimensional thiostannate has been reported so far. In the structures of thioantimonates(III) several primary building units like the [SbS3] trigonal pyramid, the [SbS4] unit or even the [SbS5] moiety are joined by vertex- and/or edge-linkages to form building blocks of higher structural hierarchy like [Sb3S4] semi-cubes or SbxSx heterocycles. A pronounced difference between thioantimonate and thiostannate chemistry is the tendency of Sb(III) to enhance the coordination geometry via so-called secondary bonds. In most cases the environment of Sb(III) is better described as a 3+n polyhedron with n = 1 - 3. The thioantimonate(V) structural chemistry is less rich than that of thioantimonates(III), and the [SbS4]3− anion shows no tendency for further condensation. By applying suitable multidentate amine molecules, transition metal cations which normally prefer bonding to the N atoms of the amines can be incorporated into the thiometallate frameworks

Facile Sodium Alginate Assisted Assembly of Ni−Al Layered Double Hydroxide Nanostructures

Self-assembled three-dimensional Ni−Al layered double hydroxide (LDH) nanostructures have been successfully synthesized using a facile biopolymer-assisted approach in the presence of a simple, safe, and inexpensive sodium alginate biopolymer under hydrothermal conditions. The structure and morphology of LDH nanostructures obtained have been investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and UV−visible diffuse spectroscopy (UV−vis). Three types of pompon-like, marigold-like, and coral-like LDH nanostructures could be obtained by adjusting the synthesis parameters including hydrothermal aging time, concentration of metal ions, and reaction temperature. A possible formation mechanism for the controlled organization of primary LDH nanosheet building units into special three-dimensional nanostructures is proposed on the basis of the interaction between sodium alginate molecules and LDH crystals. Furthermore, after calcination of LDHs at 500 and 700 °C, the resulting NiO-based mixed metal oxides still maintain the three-dimensional morphology of their LDH precursors to some extent, indicative of the high thermal stability of nanostructures. The findings in this work provide a feasible approach for the morphosynthesis of LDH nanomaterials with special superstructures.

Edge-directed [(M2)2L4] tetragonal metal–organic polyhedra decorated using a square paddle-wheel secondary building unit

A general strategy was developed for edge-directed self-assembly of tetragonal metal-organic polyhedra (MOPs) having a C(4) symmetry Cu(II)(2)(COO)(4) paddle-wheel as a secondary building unit, using C(2) symmetric dicarboxylic ligands as pincer-type primary building units.

Ternary Hydroxides II. Synthesis and Crystal Structure of the Layered Barium Hexahydroxidostannate(IV) Pentahydrate, Ba[Sn(OH)6]·5H2O

AbstractSingle crystals of Ba[Sn(OH)6]·5H2O (1) were grown by three different methods and the crystal structure was determined by X‐ray diffraction (monoclinic, P21/c, a = 10.3119(2) Å, b = 8.6079(2) Å, c = 23.4906(4) Å, β = 90.774(1)°, V = 2084.93(7) Å3, Z = 8). The fundamental primary building units (PBU′s) consist of two octahedral [Sn(OH)6]2– ions and two monocapped square antiprisms of {Ba(OH)4(H2O)5}. The latter and one of the two {Sn(OH)6} octahedra are linked together through common edges resulting in the formation of layers, the secondary building units (SBU′s). These layers can be described in terms of two {BaO9} Zweier single chains parallel to the b axis which are linked together every second antiprism through common edges with one of its two adjacent chains. The holes between these chains are filled from the {Sn(OH)6} octahedra. In contrast, the second {Sn(OH)6} octahedron has the function of a spacer separating the SBU′s from each other. Furthermore, the interlayer space is filled by five additional water molecules which are not part of any coordination sphere. All building units are held together by an extended network of hydrogen bonds with structural data that indicate medium strong to weak interactions.

Recent advances in oriented attachment growth and synthesis of functional materials: concept, evidence, mechanism, and future

The latest advances in oriented attachment controlled morphosynthesis and crystal growth of various technically important inorganic materials have been reviewed with the focus on how to generate inorganic micro-/nanostructured materials based on the so-called oriented attachment mechanism. The overview about the basic crystallization principles nowadays falls into two types, i.e., one is the classical crystal growth mode, which is via atom-by-atom additions to an existing nucleus or dissolution of unstable phases and reprecipitation of more stable phases, and the other occurs through particle based aggregation modes involving the process of mesoscopic transformation. The systematic analysis of the particle based aggregation mechanism of oriented attachment in controllable synthesis of functional inorganic materials will be described in particular. Several fashions of attachment are undertaken in the already explored reaction systems, with nanoparticles or nanoribbons as primary building units to form 1D, 2D or 3D structures, and heterostructures. The mechanism of oriented attachment could happen in systems with addition of organic additives or without, demonstrating that organic additives are not the essential factor for this kind of growth mode, which shed new light to intensive understanding of this particular phenomenon. With organic additives, i.e., reactions in organic solvents or in aqueous solution, oriented attachment events can occur too. Current developments in oriented attachment, including the basic principles and potentials with specific examples, indubitably reinforce the understanding of detailed interaction mechanisms between inorganic nanoparticles and their subsequent high order self-assembly mechanism, which are definitely promising for rationally designing various kinds of inorganic materials with ideal hierarchy, controllable length scale, and structures in solution-based systems.

Controllable Synthesis of Three-Dimensional Well-Defined BiVO4Mesocrystals via a Facile Additive-Free Aqueous Strategy

The controllable synthesis of two novel types of BiVO4 mesocrystals, with flower-like and dendrite morphology, has been successfully realized via a facile aqueous strategy. Without any additive, the primary building units perfectly aligned in three-dimension and built up well-defined mesocrystals with sharp facets and edges. The formation mechanism was further investigated, and new growth models for the mesocrystals were observed. It was found that that the pH value and reaction temperature had great influences on the formation of these unique mesocrystals. The present study not only opens new avenues for rationally designing various kinds of inorganic materials with ideal hierarchy and controllable length scale but also offers a good opportunity to understand the formation process of these unique crystalline superstructures.

Hydrothermal Synthesis and Crystal Structure of AgVMO5 (M: Se, Te).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis, characterization, and catalytic properties of hydrothermally stable macro–meso–micro-porous composite materials synthesized via in situ assembly of preformed zeolite Y nanoclusters on kaolin

Hydrothermally stable composite materials with hierarchical macro–meso–micro-porous structure were successfully synthesized via in situ assembly of preformed zeolite Y nanoclusters on kaolin using cetyltrimethylammonium bromide as template under alkaline conditions. The characterization results show that the mesophase in the composite contains primary and secondary structural building units of zeolite Y. The building units contribute micropores in the composite with acidity similar to that of zeolite Y, whereas the macroporous kaolin substrate contributes macropores. This hierarchical macro–meso–micro-porous structure increases the accessibility of the active sites in the composite to reactants and thus confers superior catalytic performance on the resulting catalyst in cracking heavy crude oil. The present work demonstrates that the in situ assembly of zeolitic nanoclusters on substrates (e.g., kaolin) can provide a novel route for fabricating composite materials with hierarchical pore structure.

Hydrothermal Synthesis and Crystal Structure of AgVMO5 (M = Se, Te)

AbstractSingle crystals of AgVSeO5 and AgVTeO5 were obtained under hydrothermal conditions at 190 °C by reacting stoichiometric amounts of AgNO3, NaVO3, TeO2 and SeO2, respectively. AgVSeO5 crystallizes in Pbcm with a = 418.14(3) pm, b = 2007.70(6) pm, c = 521.17(2) pm, V = 437.52(2) × 106 pm3 and Z = 4, as red needles. The structure consists of VO5 square pyramids, trigonal SeO3 pyramids and AgO8 polyhedra, as primary building units. The VO5 square pyramids are linked to chains running along the c‐axis, by sharing oxygen atoms in the basal plane in cis‐position. The remaining basal O atoms of the VO5 moieties are shared with two oxygen atoms of the SeO3 units. The resulting polyanionic strands of composition [VSeO5]− are interconnected by silver atoms to form a three dimensional network. AgVTeO5 crystallizes as yellow needles in P21/c with a = 586.59(1) pm, b = 1137.98(2) pm, c = 680.78(1) pm, β = 102.733(1)°, V = 443.26(1) × 106 pm3 and Z = 4. The structure consists of VO4 tetrahedra, Ψ‐trigonal‐bipyramidal TeO4 units and AgO8 polyhedra as primary building units. The TeO4 groups form dimers by edge sharing, which are linked through vertices to the VO4 tetrahedra. The resulting one dimensional polyanion is extending along [101]. The structural motifs and charge distribution according to Se4+/V5+, and Te4+/V5+ respectively, seem to allow for a reshuffling of the charge distribution, thus inducing interesting physical phenomena, at elevated temperatures or pressures.

Synthesis, Characterization and Catalytic Performance of Ti-Containing Mesoporous Molecular Sieves Assembled from Titanosilicate Precursors

Novel Ti-containing mesoporous materials with wormhole structure (Ti-WMS) can be assembled from preformed titanosilicate-1 precursors with long-chain alkylamines as structure directors. The obtained products were characterized by a series of techniques including powder X-ray diffraction, transmission electron microscopy, FT-infrared spectroscopy, UV−visible spectroscopy, N2 sorption, and hyperpolarized 129Xe NMR at variable temperature. The catalytic properties of the materials were investigated by oxidative desulfurization reactions. The results show that Ti-WMS, whose synthesis utilizes zeolite precursors as total or part of the silica and titanium sources, is a pure mesoporous phase. However, the prepared materials contain additional micropores except the uniform mesopores, which is confirmed by N2 sorption and 129Xe NMR. Infrared spectra indicate that there are zeolitic primary and secondary building units in the pore walls of Ti-WMS. UV−visible spectroscopy results confirm the existence of active Ti4+ species. Ti-WMS is very active in the oxidation of bulky sulfides such as benzothiophene, dibenzothiophene, and 4,6-dimethyl dibenzothiophene, with activities similar to Ti-HMS. However, in thiophene oxidation, which is not diffusion-limited, Ti-WMS exhibits much higher catalytic activity than Ti-HMS because of the presence of micropores and zeolite-like active sites.

Insights into the crystal growth mechanisms of zeolites from combined experimental imaging and theoretical studies

Detailed investigations into surface mediated crystal growth at zeolite external surfaces are presented. High resolution TEM is able to directly resolve surface and bulk crystallographic features and the unusual surface structural features are interpreted from simulation work. The growth of the double 4 ring is found to be a crucial and rate-determining step in the surface mediated, post-nucleation crystal growth mechanism of zeolite Beta C. Growth of 4 rings is found to be more favourable on fast growing rather than slow growing faces, explaining the relative growth rate of crystal faces in this materials. Similarly, the terminating structures of zeolite Y/Faujasite can be partly explained by considering the condensation of 6 ring and double 6 ring species at the crystal surface. Whilst 4-ring and double 4 rings are known solution species, 6 rings and double 6 rings are not, and hence it is speculated that post-nucleation crystal growth may involve competition between primary building unit and secondary building unit mediated crystal growth mechanisms.

Improvement in thermal stability and catalytic activity of titanium species in mesoporous titanosilicates by addition of ammonium salts

Mesoporous titanosilicates (MTS-9A) with thermally stable titanium species were synthesized by adding ammonium salts in the preparation procedure. Characterization results show that hexagonal mesoporous titanosilicates (MTS-9A) contain primary and secondary structural building units of zeolite in the framework, in a similar manner to MTS-9. The promoted condensation of Ti-containing silica network in MTS-9A leads to higher thermal stability of four-coordinated titanium species compared with MTS-9, as evidenced by UV–vis and 29Si NMR spectra. Catalytic tests indicate that MTS-9A samples show high activity in hydroxylation of both small (phenol) and bulky reactants (2,3,6-trimethylphenol) before and after calcination. Moreover, the recycled catalyst retains high conversion, confirming the high thermal stability of titanium species.

Crystal Engineering with the Uranyl Cation II. Mixed Aliphatic Carboxylate/Aromatic Pyridyl Coordination Polymers: Synthesis, Crystal Structures, and Sensitized Luminescence

Eleven novel U(VI)-containing coordination polymers have been synthesized under hydrothermal conditions and characterized via single-crystal X-ray diffraction and fluorescence spectroscopy. These inorganic/organic hybrid materials represent an important advance in the synthesis of polymeric materials in that multiple organic species have been employed in an effort to influence topology and properties. This family of materials is thus the result of a systematic pairing of the uranyl cation, UO22+, with aliphatic dicarboxylates (see part I, this issue) and the dipyridyl species, 4,4‘-dipyridyl and 1,2-bis(4-pyridyl)ethane. This second organic component assumes a number of roles in these structures, including direct coordination, charge balance, and structure direction. Distinction between which role(s) the dipyridyl species will assume appears to be correlated to the size (length) matching between it and the dicarboxylate linker used. Further, polymerization of primary building units (i.e., monomeric uranyl species) to form novel tetrameric secondary building units is observed in four compounds, possibly as a compensation for size differential between the organic species.

The new silver(I)thioantimonate(III) [C 4N 2H 14][Ag 3Sb 3S 7] and a new structural variant of the silver(I)thioantimonate(III) [C 2N 2H 9] 2[Ag 5Sb 3S 8] both synthesized under solvothermal conditions

The novel silver(I)thioantimonates(III) [C 4N 2H 14][Ag 3Sb 3S 7] ( I) (C 4N 2H 12=1,4-diaminobutane) and [C 2N 2H 9] 2[Ag 5Sb 3S 8] ( II) (C 2N 2H 8=ethylenediamine) were synthesized under solvothermal conditions using AgNO 3, Sb, S and the amines as structure directing molecules. Both compounds crystallize as orange needles with lattice parameters a=6.669(1) Å, b=30.440(3) Å, c=9.154(1) Å for I (space group Pnma), and a=6.2712(4) Å, b=15.901(1) Å, c=23.012(2) Å, β=95.37(1)° for II (space group P2 1/ n). In both compounds the primary building units are trigonal SbS 3 pyramids, AgS 3 triangles and AgS 4 tetrahedra. In I the layered [Ag 3Sb 3S 7] 2− anion is constructed by two different chains. An [Sb 2S 4] chain running along [100] is formed by vertex sharing of SbS 3 pyramids. The second chain contains a Ag 3SbS 5 group composed of the AgS 4 tetrahedron, two AgS 3 units and one SbS 3 pyramid. The Ag 3SbS 5 units are joined via S atoms to form the second chain which is also directed along [100]. The layered anion is then obtained by condensation of the two individual chains. The organic structure director is sandwiched by the inorganic layers and the shortest inter-layer distance is about 6.4 Å. In II the primary building units are linked into different six-membered rings which form a honeycomb-like layer. Two such layers are connected via Ag–S bonds of the AgS 4 tetrahedra giving the final undulated double layer anion. The structure directing ethylenediamine cations are located in pairs between the layers and a sandwich-like arrangement of alternating anionic layers and organic cations is observed. The inter-layer separation is about 5.4 Å. Both compounds decompose in a more or less complex manner when heated in an argon atmosphere. The optical band gaps of about 1.9 eV for the two compounds proof the semiconducting behavior. For II the conductivity was measured with impedance spectroscopy and amounts to σ 295K=7.6×10 −7 Ω −1 cm −1. At 80 °C the conductivity is significantly larger by one order of magnitude.

Solvothermal Synthesis and Crystal Structure of Mn2(C5H14N2)Sb2S5: A New Member of the Mn2(L)Sb2S5 Family (L is an Organic Structure Director)

The new compound Mn2(C5H14N2)Sb2S5 (C5H14N2 = 1,3-diaminopentane, DAPE) was prepared under solvothermal conditions using the elements as starting materials. The compound crystallizes in the orthorhombic space group Pbca with the lattice parameters a = 12.620(3), b = 11.877(2) and c = 21.814(4) Å. The primary building units are trigonal SbS3 pyramids and distorted MnS6 and MnS4N2 octahedra. These primary building blocks are joined to form Mn2Sb2S4 hetero-cubane units which are then connected via common corners, edges and faces thus forming a second type of hetero-cubane. The hetero-cubanes are condensed into layers within the (001) plane. The connection mode yields ellipsoidal pores within the layers with dimensions of about 9·7.5Å. The N atoms of the structure directing amines are exclusively bound to one of the two crystallographically independent Mn2+ cations and they point into the pores and between the layers separating the layers from each other. The interlayer separation measures about 6.7Å. Whereas the MnS6 octahedron shows only a moderate distortion the MnS4N2 octahedron is severely distorted with a remarkable long Mn-S bond length of 2.968Å.

Synthesis, characterization, and catalytic activities of mesostructured aluminophosphates assembled with preformed MFI zeolite nanoclusters

Highly stable mesostructured heteroatom-substituted AlPOs (Al-JQW-5 and Ti-JQW-5) have been successfully synthesized by assembly of MFI zeolite nanoclusters with quaternary alkylammonium surfactants under alkaline conditions. Al-JQW-5 shows a stronger acidity than conventional SAPOs using TEOS as a silica source and Ti-JQW-5 exhibits high catalytic activities in both small molecular oxidation (phenol hydroxylation) and bulky molecular oxidation (2,3,6-trimethylphenol hydroxylation). These samples have also been characterized by X-ray diffraction, transmission electron microscopy, N 2 adsorption, infrared, UV–visible spectroscopy, and a number of other techniques, and the local environment of Al, P and Si has been investigated by MAS NMR. The characterization results indicate that Al-JQW-5 and Ti-JQW-5 contain primary and secondary structural building units of MFI zeolite, which may be responsible for the stronger acidity or higher redox activities.