| 1. |
- Zhao, Jiao, et al.
(author)
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Metal-Oxide Nanoparticles with Desired Morphology Inherited from Coordination-Polymer Precursors
- 2012
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 18:11, s. 3163-3168
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Journal article (peer-reviewed)abstract
- The “escape-by-crafty-scheme” strategy is an efficient approach to prepare metal-oxide nanomaterials with desirable morphology and crystal planes inherited from coordination-polymer nanoparticle precursors, which can be designed and finely tuned by soft chemical assembly of metal ions and organic ligands at the molecular level (see scheme; ptcda=perylene-3,4,9,10-tetracarboxylic dianhydride).
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| 2. |
- Cong, Rihong, et al.
(author)
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Syntheses and Crystal Structures of Two New Bismuth Hydroxyl Borates Containing [Bi(2)O(2)](2+) Layers : Bi(2)O(2)[B(3)O(5)(OH)] and Bi(2)O(2)[BO(2)(OH)]
- 2011
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 50:11, s. 5098-5104
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Journal article (peer-reviewed)abstract
- Two new bismuth hydroxyl borates, Bi(2)O(2)[B(3)O5-(OH)] (I) and Bi(2)O(2)[BO(2)(OH)] (II), have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal and powder X-ray diffraction data, respectively. Compound I crystallizes in the orthorhombic space group Pbca with the lattice constants of a = 6.0268(3) angstrom, b = 11.3635(6) angstrom, and c = 19.348(1) angstrom. Compound II crystallizes in the monoclinic space group Cm with the lattice constants of a = 5.4676(6) angstrom, b = 14.6643(5) angstrom, c = 3.9058(1) angstrom, and beta = 135.587(6)degrees. The borate fundamental building block (FBB) in I is a three-ring unit [B(3)O(6)(OH)](4-), which connects one by one via sharing corners, forming an infinite zigzag chain along the a direction. The borate chains are further linked by hydrogen bonds, showing as a borate layer within the ab plane. The FBB in II is an isolated [BO(2)(OH)](2-) triangle, which links to two neighboring FBBs by strong hydrogen bonds, resulting in a borate chain along the a direction. Both compounds contain [Bi(2)O(2)](2+) layers, and the [Bi(2)O(2)](2+) layers combine with the corresponding borate layers alternatively, forming the whole structures. These two new bismuth borates are the first ones containing [Bi(2)O(2)](2+) layers in borates. The appearance of Bi(2)O(2)[BO(2)(OH)] (II) completes the series of compounds Bi(2)O(2)[BO(2)(OH)], Bi(2)O(2)CO(3), and Bi(2)O(2)[NO(3)(OH)] and the formation of Bi(2)O(2)[B(3)O(5)(OH)] provides another example in demonstrating the polymerization tendency of borate groups.
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| 3. |
- Du, Mingrun, et al.
(author)
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High pressure and high temperature induced polymerization of C60 solvates : The effect of intercalated aromatic solvents
- 2021
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:31, s. 17155-17163
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Journal article (peer-reviewed)abstract
- The polymerization of three typical aromatic solvent-doped fullerene materials with similar hexagonal closest packed (hcp) structures (mesitylene/C60, m-dichlorobenzene/C60 and m-xylene/C60 solvates) is studied under high pressure and high temperature (HPHT, 1.5 GPa, 573 K and 2 GPa, 700 K, respectively). Raman and photoluminescence spectroscopies reveal that the intercalated aromatic solvents play a crucial role in tailoring the extent of polymerization of C60 molecules. In the solvates, the solvents confine formation of covalent bonds between C60 molecules to the 001 direction and the (001) plane of the hcp lattices, leading to the formation of mixed polymeric phases of monomers, dimers, one-dimensional (1D) chainlike oligomers, and two-dimensional (2D) tetragonal phase polymers under suitable HPHT conditions. The type and number of substituent groups of the aromatic solvents are found to have significant influence, determining the amounts and types of polymeric phases formed. Our studies enrich the understanding of the formation mechanisms for controllably fabricating polymeric fullerenes and facilitate targeted design and synthesis of unique fullerene-based carbon materials.
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| 4. |
- Gao, Weiming, et al.
(author)
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Attachment of a Hydrogen-Bonding Carboxylate Side Chain to an FeFe -Hydrogenase Model Complex : Influence on the Catalytic Mechanism
- 2010
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In: Chemistry - A European Journal. - Weinheim : Wiley. - 0947-6539 .- 1521-3765. ; 16:8, s. 2537-2546
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Journal article (peer-reviewed)abstract
- Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4-6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the Fe Fe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of [Ru(bpy)(3)](2+), complex 1, 2, or 3, and ascorbic acid in CH3CN/D2O solution by on-line mass spectrometry.
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| 5. |
- Gao, Weiming, et al.
(author)
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Synthesis of a [3Fe2S] Cluster with Low Redox Potential from [2Fe2S] Hydrogenase Models : Electrochemical and Photochemical Generation of Hydrogen
- 2011
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In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :7, s. 1100-1105
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Journal article (peer-reviewed)abstract
- In the attempted replacement of carbon monoxide by the bis(phosphane) dppv in a dinuclear [2Fe2S] complex, a trinuclear [3Fe2S] complex with two bis(phosphane) ligands was unexpectedly obtained. On protonation, this gave a bridged hydride complex with an unusually low potential for the reduction of protons to molecular hydrogen. The redox potential also appears sufficiently positive for direct electron transfer from an excited [Ru(bpy)(3)](2+) sensitizer.
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| 6. |
- Huang, Yong, et al.
(author)
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An Air-Stable Fe3S4 Complex with Properties Similar to Those of the HOXair State of the Diiron Hydrogenases
- 2012
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In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :27, s. 4259-4263
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Journal article (peer-reviewed)abstract
- A Fe3S4 complex bridged by azapropanedithiolate (adt), complex 6, was prepared as a potential model of the HOXair state of [FeFe]-hydrogenases. Complex 6 was characterized by IR and 1H NMR spectroscopy, and its structure was determined by X-ray crystallography. The electrochemical studies show that complex 6 is redox-active under acidic conditions, which provides insight into the catalytic mechanism. Hydrogen evolution, driven by visible light, was observed in CH3CN/D2O solution by online mass spectroscopy.
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| 7. |
- Li, Mingrun, et al.
(author)
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A complicated quasicrystal approximant ε16 predicted by the strong-reflections approach
- 2010
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In: Acta Crystallographica Section B. - 0108-7681 .- 1600-5740. ; 66:part 1, s. 17-26
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Journal article (peer-reviewed)abstract
- The structure of a complicated quasicrystal approximant ϵ16 was predicted from a known and related quasicrystal approximant ϵ6 by the strong-reflections approach. Electron-diffraction studies show that in reciprocal space, the positions of the strongest reflections and their intensity distributions are similar for both approximants. By applying the strong-reflections approach, the structure factors of ϵ16 were deduced from those of the known ϵ6 structure. Owing to the different space groups of the two structures, a shift of the phase origin had to be applied in order to obtain the phases of ϵ16. An electron-density map of ϵ16 was calculated by inverse Fourier transformation of the structure factors of the 256 strongest reflections. Similar to that of ϵ6, the predicted structure of ϵ16 contains eight layers in each unit cell, stacked along the b axis. Along the b axis, ϵ16 is built by banana-shaped tiles and pentagonal tiles; this structure is confirmed by high-resolution transmission electron microscopy (HRTEM). The simulated precession electron-diffraction (PED) patterns from the structure model are in good agreement with the experimental ones. ϵ16 with 153 unique atoms in the unit cell is the most complicated approximant structure ever solved or predicted.
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| 8. |
- Lin, Sen, et al.
(author)
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Synthesis of hollow spherical tantalum oxide nanoparticles and their photocatalytic activity for hydrogen production
- 2013
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In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 199, s. 15-20
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Journal article (peer-reviewed)abstract
- Nano-particles consisting of hollow spherical tantalum oxide (referred to as HSTaO in this work) were synthesized by using the nonionic triblock copolymer F127 as the structure-directing agent in an ethanol aqueous medium. The HSTaO had a large surface area (higher than 100 m(2)/g), and relatively uniform particle size, in the range of 50-200 nm. The wall thickness of the hollow spherical particles was measured to be about 15-17 nm and contained ultrafine Ta2O5 crystallites. The band gap of HSTaO (4.3 eV) is clearly wider than that of bulk Ta2O5 (3.9 eV), which can be attributed to the quantum size of the ultrafine Ta2O5 crystallites. In addition, HSTaO with core-shell Ni/NiO particles (co-catalyst) exhibited similar photocatalytic activity as bulk Ta2O5 with co-catalyst in hydrogen generation from methanol aqueous solution under photoirradiation, with the HSTaO photocatalyst showing higher stability than the bulk.
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| 9. |
- Lindmark, Jonas, et al.
(author)
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Impregnation of zeolite membranes for enhanced selectivity
- 2010
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 365:1-2, s. 188-197
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Journal article (peer-reviewed)abstract
- A new method to enhance the selectivity of zeolite membranes for alternative separation tasks has been developed. Calcined MFI membranes were impregnated with a solution of Ca(NO3)2 in methanol and calcined at 600 °C to thermally decompose the nitrate. SEM and EDS data indicated that calcium compounds were evenly distributed in the entire MFI film and in addition, a few crystals of a calcium compound were observed on top of the film in some locations. A HR-TEM investigation showed that calcium compounds were present in low concentration in the sample and that the interiors of the MFI crystals remained fully crystalline after impregnation and calcination. However, the HR-TEM investigation could neither confirm nor rule out the occurrence of calcium compounds in the pores in the interiors of the crystals. In accordance with the SEM and TEM observations, XRD data showed that calcium compounds on top of the film were relatively large CaCO3 crystals and that the zeolite film remained crystalline after impregnation. However, eventual calcium compounds in the pores of the zeolite could not be studied by XRD since these would probably generate a very weak signal of amorphous material. FTIR data indicated that impregnation increased the amount of both physisorbed and chemisorbed CO2, the latter resulting in carbonate species in the film. n-Hexane/helium adsorption branch permporometry showed that the high quality of the membranes remained after modification. The single component permeance ratio CO2/H2 increased from 0.6 to 1.5 after impregnation. Calculations indicated that the increased CO2/H2 single component permeance ratios were both an effect of increased adsorption of CO2 in the film and reduced pressure drop in the support. The dual component separation factor α CO2/H2 at room temperature increased drastically from 0.7 (H2 selective) to 3.4 (CO2 selective) after impregnation. This work shows for the first time that impregnation procedures can be used to tailor the diffusion properties of zeolite membranes in a similar way as impregnation procedures are used to tailor the catalytic performance of catalysts.
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| 10. |
- Liu, Leifeng, et al.
(author)
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Structure determination of [3Fe2S] complex with complicated pseudo-merohedric twinning
- 2012
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In: Zeitschrift fur Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 227:4, s. 221-226
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Journal article (peer-reviewed)abstract
- A route of solving crystal structures from complicated pseudo-merohedric twinning crystals was described. The structure of a [3Fe2S] complex was solved and refined in the space group of P42/n to R1 factor of 0.1789. Consequently, by deleting one of the two disordered groups in the structure, a space group of Aea2 for the absolute structure was found. The new absolute structure with four twinning components was refined to R1 about 0.1171. At the final stage, the disorder was again added to the structure. The structure in space group Aea2 with both twinning and disorder was refined to R1 of 0.0722, which implies the special structure feature.
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| 11. |
- Sun, Junliang, et al.
(author)
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The ITQ-37 mesoporous chiral zeolite
- 2009
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 458, s. 1154-1157
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Journal article (peer-reviewed)abstract
- The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest. The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis of ITQ-33, a stable zeolite with 18 × 10 × 10 ring windows, and the synthesis of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction (SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm. The framework follows the SrSi2 (srs) minimal net and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 Å3) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm3 g-1. Keywords: srs-net, powder X-ray, charge flipping, electron microscopy
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| 12. |
- Yang, Xigui, et al.
(author)
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Polarized Raman study of aligned multiwalled carbon nanotubes arrays under high pressure
- 2015
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:49, s. 27759-27767
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Journal article (peer-reviewed)abstract
- Tuning the intertube interaction and the topological structure of carbon nanotubes by the application of pressure may obviously affect their properties such as optical and electronic properties. However, characterizing such changes is still challenging. Here, we performed polarized Raman scattering studies on aligned multiwalled carbon nanotube arrays (MWNTAs). Unlike researchers from the previous literature, we found that the MWNTAs exhibit a polarization dependence similar to that of isolated single walled carbon nanotubes at ambient conditions. Upon compression, the polarization dependence weakens gradually with increasing pressure up to ∼20 GPa, which has been discussed in terms of pressure-induced enhancement of intertube interactions. At around 20 GPa, the depolarization effect vanishes, which can be explained by the formation of interlinked sp3 bonding in the MWNTAs. Our results show that polarized Raman spectroscopy is an efficient method to explore not only intertube interaction but also structural transition changes in MWNTs, which overcome the difficulty that MWNTs have no obvious fingerprints like those of single-walled carbon nanotubes in the study of structural transformations.
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| 13. |
- Zhang, Ying, et al.
(author)
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Capture of novel sp3 hybridized Z-BN by compressing boron nitride nanotubes with small diameter
- 2022
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In: Diamond and related materials. - : Elsevier. - 0925-9635 .- 1879-0062. ; 130
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Journal article (peer-reviewed)abstract
- Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.
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