Room temperature solution-phase synthesis of flower-like nanostructures of [Ni3(BTC)2·12H2O] and their conversion to porous NiO

Hierarchical flower-like architectures of[Ni₃（BTC）₂·12H₂O]（BTC³=benzene-1,3,5-tricarboxylate） were successfully prepared by a simple solution-phase method under mild conditions without any template or surfactant.Phase-pure porous NiO nanocrystals were obtained by annealing the Ni-BTC complex without significant alteration in morphology.The product was characterized by X-ray diffraction techniques,field-emission scanning electron microscopy（FESEM）.transmission electron microscopy（TEM） and high-resolution TEM（HRTEM）.The catalytic effect of the NiO product was investigated on the thermal decomposition of ammonium perchlorate（AP） and it was found that the annealed NiO product has higher catalytic activity than the commercial NiO.     

Optimization of strontium- doping concentration in BaTiO3 nanostructures for room temperature NH3 and NO2 gas sensing

In this study, we comprehensively present the gas sensing performance of strontium (Sr)-doped barium titanate (BaTiO₃) nanostructures which are synthesized by a low-temperature hydrothermal route. The in-situ doping of strontium in BaTiO₃ nanostructures is achieved with different molar concentrations of Sr, and the sensing performance was evaluated by screen printing process of products to form their thick films. The thick films of as-prepared Sr-doped BaTiO₃ (BaSrTiO₃) were investigated for gas sensing performance for various gases at different operating temperatures where strong response was observed for both nitrogen dioxide (NO₂) and ammonia (NH₃) gases at room temperature. Furthermore, the sensing response at room temperature for NH₃ and NO₂ gases was also studied with respect to Sr doping concentrations in BaTiO₃ nanostructures.     

Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption-desorption measurements.     

Effect of synthesis time and treatment on porosity of mesoporous silica materials

Nitrogen adsorption at 77 K on mesoporous silica materials (MPS) with varying synthesis time and treatment conditions was investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were also used to characterize the mesoporous materials. This study was performed at 6, 24 and 72-h synthesis times. It is shown that 6-h is not enough for complete formation of the MPS material and at least 24-h is necessary. The pore structure starts decaying for the 72-h synthesis time. The three-after-synthesis treatment conditions used were 1) washed, 2) washed and calcined and 3) directly calcined after synthesis. Ethanol/HCl mixtures were used for washing and calcinations were performed at 550°C. Among these samples, directly washed sample yields the lowest adsorption capacity while washed and calcined sample yields the highest adsorption capacity. Hence, it is concluded that washing stabilizes the structure before high temperature treatment.     

Adsorption of xylene isomers on ordered hexagonal mesoporous FDU-15 polymer and carbon materials

The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers. The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the feasibility of using the three isomers as adsorbates to extract pore information. This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec.     

微介孔材料物理吸附准确性分析的理论与实践

比表面积和孔径分布是表征催化剂和材料物理性质的基本参数,随着材料研究的日益广泛和深入,研究工作者对该参数的科学性和准确性要求日益提高. 但是,比表面积和孔径分布的分析方法—物理吸附法,长期以来被看作一种测量方法,其准确性并不为人们所关注,在实际工作中对其的理解存在着大量的误区. 本文从仪器硬件设计、实验操作及数据处理三方面对物理吸附法所涉及的准确度进行了探讨.     

A novel template-free sol–gel synthesis of silica materials with mesoporous structures and zeolitic walls

Hierarchical porous materials with zeolite structures show great promise in catalysis due to combining the advantages of zeolites and mesoporous materials. Here a novel template-free sol–gel method is developed to synthesize hierarchical porous silica materials. This method involves solvothermal recrystallization of the xerogel converted from uniform silicalite-1 precursor sol via vacuum drying process. The zeolite sol and the solid samples were characterized by laser light scattering, XRD, N₂ adsorption/desorption isotherm, FTIR, SEM, TEM and thermal analysis technologies. The results show that we obtain two novel materials with different mesoporous structures and silicalite-1 walls by using different recrystallization media, one of which has irregular arrays of mesopores, the other possesses 3D wormhole mesoporous structure. We speculate that formation of different mesoporous structures results from different nucleation and growth process of materials     

Characterization and acidic properties of Al-SBA-15 materials prepared by post-synthesis alumination of a low-cost ordered mesoporous silica

A series of Al-containing SBA-15 type materials with different Si/Al ratio, were prepared by post-synthesis modification of a pure highly ordered mesoporous silica SBA-15 obtained by using sodium silicate as silica source, and amphiphilic block copolymer as structure-directing agent. A high level of aluminum incorporation was achieved, reaching an Si/Al ratio of up to 5.5, without any significant loss in the textural properties of SBA-15. These materials were fully characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ²⁷Al NMR spectroscopy, and N₂ adsorption at 77 K. The acid properties of these materials have been evaluated by NH₃-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FTIR spectroscopy. The effective acidity of these materials was evaluated using two catalytic reactions: 2-propanol dehydrogenation and 1-butene isomerization. The adsorption of basic probe molecules and the catalytic behavior revealed an evolution of the acid properties with the Al content. These studies have shown that the Al-SBA-15 materials contain Brønsted and Lewis acid sites with medium acidity which makes them appropriate to be used as acid catalysts in heterogeneous catalysis, catalytic supports, and adsorbents.     

Bridged amine-functionalized mesoporous organosilica materials from 1,2-bis(triethoxysilyl)ethane and bis[(3-trimethoxysilyl)propyl]amine

Amine-functionalized, organic/inorganic hybrid mesostructured organosilica (BAFMO) materials have been synthesized and characterized from two bridged silsesquioxane precursors, 1,2-bis(triethoxysilyl)ethane (BTESE) and bis[(3-trimethoxysilyl)propyl]amine (BTMSPA). Mole ratios of BTESE ranged from 0.05, 0.10, 0.125, to 0.175. The synthetic pathway involves employing cetyltrimethylammonium bromide as a template under basic conditions at room temperature. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies revealed that the resultant BAFMO materials possess mesocopically ordered, hexagonal symmetries and well-defined morphologies. However, the order was decreased as the amount of BTMSPA increased, in terms of the d₁₀₀ spacings and the unit cell parameters on XRD as well as the TEM images. N₂ gas sorption experiments showed a gradual decrease in both the surface area, from 1075 to 688 m²/g, and the pore volume, from 2.08 to 0.55 cm³/g, on increasing the amount of BTMSPA. The organic functionalization was successfully determined by Fourier-transform infrared and ¹³C CP MAS NMR spectroscopy. X-ray photoelectron spectroscopy and elemental analysis results also confirmed the presence of Si-C bond as well as amine functionalities in the solvent-extracted mesoporous organosilica materials.     

抑制剂对大肠杆菌作用的透射电镜及微量热法研究

用透射电镜对大肠杆菌以及大肠杆菌受到３种不同抑制剂抑制时的形态进行了观察，结果发现不同的抑制剂对大肠杆菌的不同抑制作用表现在大肠杆菌的微观形态发生了不同的变化，同时结合微量热的方法，测试了３种不同抑制剂作用下大肠杆菌的生长代谢热谱，热谱曲线的分析结果与透射电镜观察结果吻合。     

Studies on the thermal stability of nano-SiC powder with excessive free carbon by TG-DTA-MS, XRD and TEM

We studied the removal process of excessive free carbon in the nano-SiC powder by TG-DTA-MS, XRD and TEM three methods. The studies showed that the temperature of removing excessive free carbon in the nano-SiC powder should be about 750°C in air.     

Structural studies on polymer whiskers by transmission electron microscopy. II. Unit cell of poly(p‐hydroxybenzoic acid) whisker crystal at room temperature

A set of conspicuous reflections, which are not indexed using the cell constants reported so far for poly(p‐hydroxybenzoic acid), were found in the electron diffraction (ED) patterns of its whisker crystal. A new unit cell [a = 1.487 nm, b = 0.572 nm, and c (chain axis) = 1.258 nm, α = β = γ = 90°] was proposed to explain the reflections in question, based on a set of the ED patterns viewed along the different zone axes, which were obtained by tilting the whisker around its long axis. The density of the whisker was experimentally measured to be 1.500 g/cm³, showing that four molecular stems are running through the new unit cell. From the extinction rule, the highest space group was assumed to be Pbca. In this case, the projection of the new unit cell onto the ab‐plane gives a two‐dimensional unit cell with pgm and is basically in agreement with those proposed so far. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2456–2462, 1999     

Simultaneous determination of nitroaromatic compounds in water using capillary electrophoresis with amperometric detection on an electrode modified with a mesoporous nano‐structured carbon material

In this article, a carbon disk electrode modified with mesoporous carbon material (CMK‐3) was used in CE with amperometric detection system for the simultaneous determination of four types of important nitroaromatic compounds, including 2,4,6‐trinitrotoluene (TNT), 1,3,5‐trinitrobenzene (TNB), 2,4‐dinitrotoluene (DNT) and 1,3‐dinitrobenzene (DNB). Compared with the bare carbon electrode, the CMK‐3 modified electrode greatly improved the sensitivity at a relatively positive detection potential due to its excellent electrocatalytic activities, high conductivity and large effective surface area. The four analytes could be well separated and detected within 480 s. A good linear response was obtained for TNB, DNB, TNT and DNT from 8.4 to 5.0×10³ μg/L, with correlation coefficients higher than 0.9992. And the detection limits were established between 3.0 and 4.7 μg/L for the four investigated nitroaromatic compounds (S/N=3). The CMK‐3‐modified electrode was successfully employed to analyze coking wastewater, tap water and river samples with recoveries in the range of 94.8–109.0%, and RSDs less than 5.0%. The presented results demonstrated that the CMK‐3‐modified carbon electrode used in CE with amperometric detection was of convenient preparation, high sensitivity and good repeatability, which could be employed in the rapid determination of practical samples.     

Heterogeneous chiral Mn(III) salen catalysts for the epoxidation of unfunctionalized olefins immobilized on mesoporous materials with different pore sizes

Two chiral Mn(III) salen complexes were immobilized onto a series of mesoporous MCM-41 and MCM-48 materials with different pore sizes and the as-synthesized catalysts were active and enantioselective for the asymmetric epoxidation of styrene and indene. The results of XRD, FTIR, DR UV-vis, and N₂ sorption showed that the chiral Mn(III) salen complexes were anchored in the channels of mesoporous materials. The influence of organic silicane dosage on the catalytic performance was studied and the optimum dosage of organic silicane for preparing heterogeneous catalysts was determined. Furthermore, the effect of the fine-tuning of pore size on the performance of heterogeneous catalysts was discussed. In general, larger pore size of the supports could lead to higher conversions and the compatible pore size with substrate may be responsible for the improved enantiomeric excess (ee) values.     

In situ grafting of cyclopentadienyl-molybdenum complexes on mesoporous materials: The reaction of [η-CpMo(CO)3]Na with surface fixed iodo-benzyl siloxane

Na⁺[η⁵-CpMo(CO)₃]⁻ is grafted on aromatic silane (iodo-benzyl trimethoxy silane) modified surfaces of MCM-41 and MCM-48 molecular sieves. The XRD, N₂ adsorption-desorption, and TEM analysis provide strong evidence that the mesoporous structure of the supporting materials retains its long range ordering after the grafting process, despite significant reductions of the surface area, pore-volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm⁻¹ as well as 3010 cm⁻¹ on the grafted samples showing the presence of carbonyl as well as aromatic functional groups, evidences the successful grafting of the η⁵-CpMo(CO)₃ complexes. Elemental analysis reveals 6.4 and 8.3 wt% Mo on the SM-41ASG and SM-48ASG samples, respectively. The appearance of new ²⁹Si CP MAS-NMR peaks around −61.4, and −69.6 ppm (T₂ and T₃) indicates the esterification of silanol groups by the methoxy group of the silane ligand. The samples prepared by this in situ method show high loading of Mo and also good catalytic activity and selectivity for olefin-epoxidation.     

Grafting of η-Cp(COOMe)MoCl(CO)3 on the surface of mesoporous MCM-41 and MCM-48 materials

η⁵-Cp(COOMe)MoCl(CO)₃ is grafted on the surface of mesoporous MCM-41 and MCM-48 materials through available silanol groups. The structural intactness of the supporting materials is confirmed by powder XRD and N₂ adsorption analysis. The presence of the Mo complex on the surface is confirmed by FT-IR and elemental analysis. The catalysts are successfully applied for cyclooctene epoxidation.     

Electrochemistry and biosensing of glucose oxidase based on mesoporous carbons with different spatially ordered dimensions

A strategy of protein entrapment within mesoporous carbon matrices is demonstrated to probe the electrochemistry of glucose oxidase. Large surface area and remarkable electro-catalytic properties of carbon mesoporous materials make them suitable candidates for high loading of protein molecules and the promotion of heterogeneous electron transfer. In this work, two kinds of mesoporous carbon nanocomposite films were designed and prepared with highly ordered two-dimensional (2D) and three-dimensional (3D) structures for the immobilization of glucose oxidase, in which the quasi-reversible electron transfer of the redox enzyme was probed, and the apparent heterogeneous electron transfer rate constants () are 3.9 and 4.2 s⁻¹, respectively. Furthermore, the associated biocatalytic activity was also revealed. Highly ordered 3D-mesoporous carbon material exhibited larger adsorption capacity for glucose oxidase and the immobilized enzymes retained a higher bioactivity compared with 2D-mesoporous carbons. The preparation of protein-entrapped mesoporous carbon nanocomposites expands the scope of carbon-based electrochemical devices and opens a new avenue for the development of biosensors.     

Study on the controllable synthesis of SH-MCM-41 mesoporous materials and their adsorption properties of the La3+, Gd3+ and Yb3+

Sulfhydryl MCM-41 (SH-MCM-41) mesoporous materials were prepared via a hydrothermal method, and -SH was successfully imported by a post-grafting method. The structure and surface properties of the materials were characterized using Fourier Transform infrared spectroscopy, X-ray diffraction and Transmission Electron Microscopy analysis. The low concentrations of La³⁺, Gd³⁺ and Yb³⁺ adsorption on the material were investigated. This paper discusses the effects of system factors, such as pH and the solid-liquid ratio, on the performance of the adsorption process. The adsorption thermodynamics and kinetics were also explored. Experimental results indicated that the materials were in good order and had high specific surface area (956 m²/g) with an average pore diameter of 2.1 nm; the mercapto groups were successfully grafted onto a molecular sieve, and the best grafted amount was 1.46 × 10^?3 mol/g. The materials showed preferable adsorption of La³⁺, Gd³⁺ and Yb³⁺ with maximum adsorption capacities of 560.56 mg/g, 467.60 mg/g and 540.68 mg/g, respectively. The adsorption process can be described by the Freundlich isotherm model, and the adsorption data fits pseudo-second-order kinetics. After repeating the elution-regeneration cycle four times, the adsorption capacity of rare earth ions was mostly maintained, indicating that the adsorbent can be regenerated well and recycled to save costs. It has potential in practical application.     

The effect of F-doping and temperature on the structural and textural evolution of mesoporous TiO2 powders

Mesoporous F⁻-doped TiO₂ powders were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in a mixed NH₄F-H₂O solution. Effects of F⁻ ion content and calcination temperatures on the phase composition and porosity of mesoporous titania were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and BET surface areas. The results showed the BET surface area (S_BET) of the pure and doped powders dried at 100°C ranged from 260 to 310 m²/g as determined by nitrogen adsorption. With increasing calcination temperatures, the S_BET values of the calcined titania powders decreased due to the increase in crystalline size. The pore size distribution was bimodal with fine intra-particle pore and larger inter-particle pore as determined by nitrogen adsorption isotherms. The peak pore diameter of intra-particle pore increases with increasing F⁻ ion content. At 700°C, all the titania powders exhibit monomodal pore size distributions due to the complete collapse of the intra-particle pores. The crystallization of anatase was obviously enhanced due to F⁻-doping at 400°C and 500°C. Moreover, with increasing F⁻ ion concent, F⁻ ions not only suppressed the formation of brookite phase at low temperature, but also prevented phase transition of anatase to rutile at high temperature.     

Chemical studies on the reactions of synthetic 1.13-nm-tobermorite with alkali metal hydroxides at room temperature

Summary The reaction of alkali metal hydroxides (MOH;M=Li, Na, K;c=0.02–1.0M) with synthetic 1.13-nm-tobermorite (Ca₅Si₆H₂O₁₈·4H₂O) at 25±2°C was studied. The results obtained indicate that the reactivity highly depends onpH and cation field strength and to lesser degree on the ionic radius ofM. MOH has negative effects on the crystallinity of the concerned phase in the following order: KOH > NaOH > LiOH. Furthermore, the hydroxides cause swelling of crystals, attributable to the creation of new cavities due to partial hydrolysis of tetrahedral SiO₂(OH)₂ chains in the lattice. Hydrolysisvia cleavage of Si-O-Si bonds facilitates the cation exchange process Ca²⁺ M ⁺ which probably proceeds by a nucleophilic substitution reaction (S_N2). The observed different affinities of 1.13-nm-tobermorite towardsMOH could be used for the separation of these cations.

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Chemische Untersuchung der Reaktion von synthetischem 1.13-nm-Tobermorit mit Alkalimetallhydroxiden bei Raumtemperatur

Zusammenfassung Die Reaktion von Alkalimetallhydroxiden (MOH;M=Li, Na, K;c=0.02–0.1M) mit synthetischem 1.13-nm-Tobermorit (Ca₅Si₆H₂O₁₈·4H₂O) wurde bei 25±2°C untersucht. Die Ergebnisse zeigen, daß die Reaktivität stark vompH-Wert und von der Kationenfeldstärke, hingegen weniger vom Ionenradius des verwendeten Alkalimetalls abhängt.MOH wirkt sich in der Reihenfolge KOH > NaOH > LiOH negativ auf die Kristallinität der betroffenen Phasen aus. Darüber hinaus verursachen Hydroxide eine Schwellung der Kristalle, ausgelöst durch die Erzeugung neuer Hohlräume durch partielle Hydrolyse tetraedrischer SiO₂(OH)₂-Ketten im Kristallgitter. Hydrolyse der Si-O-Si-Bindungen erleichtert den Kationenaustauschprozeß zwischenM ⁺ und Ca²⁺, welcher wahrscheinlich über einen S_N2-Mechanismus verläuft. Die beobachteten Unterschiede in der Reaktivität zwischenMOH und 1.13-nm-Tobermorit eröffnen eine Möglichkeit zur Trennung dieser Kationen.