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11.
A new procedure for the preparation of high aspect ratio Au nanowires utilizing gold electroless reduction in the hexagonally ordered, thiol-modified nanosized channels of the SBA-15 material is reported. Two different Au precursors were adsorbed onto pedant thiol groups, covalently bonded to the mesoporous silica surface, and used as seeds to grow extended Au nanostructures by treatment in Au electroless reduction bath. It is shown that the dimensions and the assembly of the Au seeds are important parameters for the subsequent electroless reduction process. The [AuCl4]- ions complexed to the TOAB molecules assembled on the thiol-modified mesoporous surface of the SBA-15 material are suitable precursors for the subsequent gold electroless reduction. The resulting structures are several micrometer long Au nanowires with uniform diameters of about 5 nm, having large single-crystalline domains. The TEM results clearly show that the growth of the Au nanowires is templated by the channel structure of the SBA-15 material. 相似文献
12.
Following the strategy of using polyfunctional phosphonic acids for the synthesis of open-framework metal phosphonates, the phosphonocarboxylic acid (H2O3PCH2)2NCH2C6H4COOH was used in the hydrothermal synthesis of new Ba phosphonates. Its decomposition led to the first open-framework barium phosphonate [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O. The synthesis was also successfully performed using iminobis(methylphosphonic acid), (H2O3PCH2)2NH, as a starting material, and the synthesis was optimized to obtain as a pure material. The reaction setup as well as the pH are the dominant parameters, and only a diffusion-controlled reaction led to the desired compound. The crystal structure was solved from single-crystal data: monoclinic; C2/c; a=2328.7(2), b=1359.95(7), and c=718.62(6) pm; beta=98.732(10) degrees ; V=2249.5(3)x10(6) pm3; Z=4; R1=0.036; and wR2=0.072 (all data). The structure of [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O is built up from BaO8 and BaO10 polyhedra forming BaO chains and layers, respectively. These are connected to a three-dimensional metal-oxygen-metal framework with the iminobis(methylphosphonic acid) formally coating the inner walls of the pores. The one-dimensional pores (3.6x4 A) are filled with H2O molecules that can be thermally removed. Thermogravimetric investigations and temperature-dependent X-ray powder diffraction demonstrate the stability of the crystal structure up to 240 degrees C. The uptake of N,N-dimethylformamide and H2O by dehydrated samples is demonstrated. Furthermore, IR, Raman, and 31P magic-angle-spinning NMR data are also presented. 相似文献
13.
Dr. Mostakim SK Dr. Soumitra Barman Shounik Paul Ratnadip De Dr. S. S. Sreejith Dr. Helge Reinsch Dr. Maciej Grzywa Dr. Norbert Stock Prof. Dr. Dirk Volkmer Dr. Shyam Biswas Prof. Dr. Soumyajit Roy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):4098-4107
A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h−1 in addition to oxygen, which was produced with a TOF of 0.54 h−1. No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here. 相似文献
14.
15.
16.
Dr. Mark Feyand Milan Köppen Prof. Dr. Gernot Friedrichs Prof. Dr. Norbert Stock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(37):12537-12546
A systematic investigation of the systems Bi3+/carboxylic acid/HNO3 for the tri‐ and tetracarboxylic acids pyromellitic acid (H4Pyr), trimellitic acid (H3Tri) and trimesic acid (H3BTC) acid led to the discovery of five new bismuth carboxylates. Structural characterisation allowed the influence of the linker geometry and the Bi3+:linker molar ratio in the starting solution on the crystal structure to be determined. The crystallisation of three selected compounds was investigated by in situ energy‐dispersive X‐ray diffraction. Three new crystalline intermediates were observed within minutes, and two of them could be isolated by quenching of the reaction mixture. Their crystal structures were determined from laboratory and synchrotron X‐ray powder diffraction data and allowed a possible reaction pathway to be established. In depth characterisation of the luminescence properties of the three bismuth pyromellate compounds was carried out. Fluorescence and phosphorescence could be assigned to (mainly) ligand‐ and metal‐based transitions. The polymorphs of Bi(HPyr) exhibit different luminescence properties, although their structures are very similar. Surprisingly, doping of the three host structures with Eu3+ and Tb3+ ions was only successful for one of the polymorphs. 相似文献
17.
Pia Rönfeldt Helge Reinsch Erik Svensson Grape A. Ken Inge Huayna Terraschke Norbert Stock 《无机化学与普通化学杂志》2020,646(16):1373-1379
A new scandium naphthalenedicarboxylate with the framework composition [Sc2(1,4-NDC)3] (H2-1,4-NDC = 1,4-naphthalenedicarboxylic acid) was obtained under hydrothermal synthesis conditions. A structure model could be developed by a combination of 3D electron diffraction measurements and computationally assisted structure determination, which was further validated by a good agreement with the experimental powder X-ray diffraction pattern. The structure consists of isolated ScO6 octahedra interconnected by the carboxylate groups of linker molecules to form chains. These chains are connected by the naphthalene-moieties to form a three-dimensional framework with square-shaped pores and the organic group pointing into the pores. Although very similar synthesis conditions were chosen, [Sc2(1,4-NDC)3] is not isostructural to aluminum naphthalenedicarboxylate [Al(OH)(1,4-NDC)], which crystallizes in a MIL-53 type structure. This can be traced back to the different inorganic building units that are observed. The compound was thoroughly characterized by elemental analysis, IR spectroscopy, sorption measurements, thermogravimetric analysis and luminescence measurements. [Sc2(1,4-NDC)3] exhibits a high thermal stability and a ligand-based blue luminescence in the solid state at room temperature. 相似文献
18.
K. Bangert U.E.P. Berg G. Junghans R. Stock K. Wienhard H. Wolf 《Nuclear Physics A》1976,261(1):149-173
The electric giant dipole resonance of 24?26Mg has been explored up to 30 MeV excitation energy with bremsstrahlung. ΔE, E spectra of charged photo-particles and spectra of prompt deexcitation γ-rays from excited residual nuclear states were obtained at various bremsstrahlung endpoint energies. The 25Mg(γ, p0), (γ, d), 24,25Mg(γ, α) differential cross sections as well as 24?26Mg(γ, xγ′) integrated cross sections are presented. The results are discussed in terms of one-particle, one-hole excitations and isospin composition of giant resonance states. A comparison with calculations for 24Mg gives poor agreement. Excitations from deeper shells were found in the giant dipole resonance of 24Mg, but do not seem to be concentrated at higher energies. In 25Mg, only weak excitations of this kind were found, and they are completely absent in 26Mg. 相似文献
19.
Zusammenfassung Am Beispiel des Systems Na4(VO3)4-NaCl-H2O wird untersucht, in welcher Weise Ultrazentrifugenmessungen im Sedimentationsgleichgewicht durchgeführt werden müssen, um die molare Masse und die Ladungszahl von Polymerelektrolyten in ternären Systemen unter der Bedingung von nicht vernachlässigbaren Wechselwirkungen zwischen Polymerund Fremdelektrolyt zu bestimmen. Es erweist sich, daß die experimentellen scheinbaren molaren Massen nicht nur auf die Polymerkonzentration Null extrapoliert werden müssen, sondern auch auf die Fremdelektrolytkonzentration Null. Es gelingt, die Ableitung (alnyPXz/amBx)mPXz an der StellemPXz = 0 mol kg-1 mit einer scheinbaren mittleren Ladungszahlz
app
des Polymeranions zu korrelieren. Zwischen dieser und der stöchiometrischen Ladungszahlz des Polymeranions besteht die Beziehungz
app
= Z =az, so daß die Dissoziationskonstante des Polymerelektrolyten für die summarische Dissoziation berechnet werden kann. Die aus dieser Korrelation folgenden Abhängigkeiten der scheinbaren mittleren Ladungszahlen und der Ableitung (alnypx
z
/amBX)Mpx
z
= 0 von der Konzentration des Fremdelektrolyten werden experimentell bestätigt.
Mit 4 Abbildungen und 4 Tabellen 相似文献
Summary The system Na4(VO3)4-NaCl-H20 is taken as an example for ultracentrifugal measurements at sedimentation equilibrium to determine the molar mass and the valency of a polymer electrolyte in a ternary system when interactions exist between the polymer and the supporting electrolyte. The experimental apparent molar mass is obtained by extrapolation to zero value of concentration of both the polymeric and supporting electrolyte. It is possible to correlate the quantity (alnyPX z /amBX)mPXz at the point m PX z = 0 mole kg-1 with the apparent valency zapp of the polymeric anion.z app is related to the stoichiometric valency by the equationz app = z =a.Z. Thus the dissociation constant can be calculated for complete dissociation of the polymer electrolyte. The dependence of zapp and (aln y PX z /a m BX ) m PX z = 0 on concentration of the supporting electrolyte called for in the correlation is verified experimentally.
Mit 4 Abbildungen und 4 Tabellen 相似文献
20.