立方Nd2O3上过氧物种光诱导生成的18O同位素示踪考察

采用原位显微Raman光谱和¹⁸O同位素示踪技术,以325 nm激光为激发光源,对立方Nd₂O₃上过氧物种的光诱导生成过程进行了详细表征,进一步证实过氧源于分子氧对晶格氧的氧化反应. 结果还表明,325 nm激光在室温下即可诱导过氧的生成,在实验条件下,生成的过氧物种可与Nd₂O₃的晶格氧发生快速的氧交换反应,位于Nd₂O₃体相的晶格氧也可迁移至样品表层进而参与过氧的生成. 325 nm激光照射有助于促进晶格氧的迁移以及晶格氧与分子氧之间的氧交换反应.     

Hybrid Mesoporous-Silica Materials Functionalized by PtII Complexes: Correlation between the Spatial Distribution of the Active Center,Photoluminescence Emission,and Photocatalytic Activity

[Pt(tpy)Cl]Cl (tpy: terpyridine) was successfully anchored to a series of mesoporous-silica materials that were modified with (3-aminopropyl)triethoxysilane with the aim of developing new inorganic–organic hybrid photocatalysts. Herein, the relationship between the luminescence characteristics and photocatalytic activities of these materials is examined as a function of Pt loading to define the spatial distribution of the Pt complex in the mesoporous channel. At low Pt loading, the Pt complex is located as an isolated species and exhibits strong photoluminescence emission at room temperature owing to metal-to-ligand charge-transfer (³MLCT) transitions (at about 530 nm). Energy- and/or electron-transfer from ³MLCT to O₂ generate potentially active oxygen species, which are capable of promoting the selective photooxidation of styrene derivatives. On the other hand, short Pt⋅⋅⋅Pt interactions are prominent at high loading and the metal-metal-to-ligand charge-transfer (³MMLCT) transition is at about 620 nm. Such Pt complexes, which are situated close to each other, efficiently catalyze H₂-evolution reactions in aqueous media in the presence of a sacrificial electron donor (EDTA) under visible-light irradiation. This study also investigates the effect of nanoconfinement on anchored guest complexes by considering the differences between the pore dimensions and structures of mesoporous-silica materials.     

Vibrational study on the cobalt binding mode of Carnosine

The Co(II)-l-Carnosine (Carnos) system was investigated at different pH and metal/ligand molar ratios by Raman and IR spectroscopy. Raman spectra present some marker bands yielding information on the ability of the Co(II)/Carnos system to bind molecular oxygen and to identify the metal co-ordination site of the imidazole ring (N_π or N_τ atom) of Carnos.The existence of different oxygenated species is greatly affected by pH and the structure of the predominant complexes depends on the available nitrogen atoms. Under basic conditions, binuclear complexes binding molecular oxygen are the predominant species and two forms (monobridged and dibridged) were identified by the Raman νO-O band (750-850 cm⁻¹).Decreasing pH to 7, the species present in the system are less able to bind oxygen. Hydrogen peroxide and a Co(III) chelate not binding O₂, were formed with a significant conversion of peroxo into superoxo complexes. A slight excess of Carnos does not enhance metal chelation.In slightly acidic conditions, the formation of H₂O₂ and superoxo species is more enhanced than at pH 7 and another Co(III) chelate is probably formed.     

Sol-gel synthesis of mesoporous CaCu3Ti4O12 thin films and their gas sensing response

A new sol-gel synthesis procedure of stable calcium copper titanate (CaCu₃Ti₄O₁₂—CCTO) precursor sols for the fabrication of porous films was developed. The composition of the sol was selected in order to avoid the precipitation of undesired phases; ethanol was used as solvent, acetic acid as modifier and poly(ethyleneglycol) as a linker agent. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 °C. The main phase present in the samples, as detected by X-ray diffraction and Raman spectroscopy, was CaCu₃Ti₄O₁₂. Scanning electron microscopy analysis showed that mesoporous structures, with thicknesses between 200 and 400 nm, were developed as a result of the processing conditions. The films were tested regarding their sensibility towards oxygen and nitrogen at atmospheric pressure using working temperatures from 200 to 290 °C. The samples exhibited n-type conductivity, high sensitivity and short response times. These characteristics indicate that CCTO mesoporous structures obtained by sol-gel are suitable for application in gas sensing.     

Synthesis and characterization of Zr-SBA-15 supported tungsten oxide as a new mesoporous solid acid

A series of materials WO₃/Zr-SBA-15 were synthesized by modifying zirconium-incorporated SBA-15 mesoporous molecular sieve with various loadings of tungsten oxide, followed by calcining at different temperatures. The structures and the surface states of these materials were determined by XRD, TEM, N₂ adsorption–desorption and Raman spectroscopy, while the surface acidities were characterized by FT-IR spectroscopy of pyridine adsorption, NH₃-TPD, and the Hammett indicator method. To evaluate the catalytic activities of the prepared materials, the benzoylation of anisole was chosen as the model reaction. All the results reveal that the synthesized samples are strong solid acids, even solid superacids under some conditions, with uniform mesoporous structure and high surface area. The dispersion state of the supported WO₃, which depends on the WO₃ loading and the calcination temperature, has a direct influence on the acidity and catalytic activity of the materials. Moreover, the high acid strength is attributed to the WO bond nature of the complex formed by the interaction between WO₃ and the surface of Zr-SBA-15.     

Raman, XRD and microscopic investigations on CeO2-Lu2O3 and CeO2-Sc2O3 systems: A sub-solidus phase evolution study

A sub-solidus phase evolution study was done in CeO₂-Sc₂O₃ and CeO₂-Lu₂O₃ systems under slow-cooled conditions from 1400 °C. Long-range order probing of X-ray diffraction technique is utilized in conjunction with the ability of Raman spectroscopy to detect the changes in local co-ordination. Lu₂O₃ showed solubility of 30 mol% in CeO₂, thus forming an anion deficient fluorite-type (F-type) solid solution, whereas Sc₂O₃ did not show any discernible solubility. A biphasic region (F+C) was unequivocally detected by Raman spectroscopy in Ce_1−xLu_xO_2−x/2 (0.4?x?0.9) and in Ce_1−xSc_xO_2−x/2 (0.1?x?0.9) systems. Raman spectroscopy was valuable in studying these systems since oxygen vacancies are created on doping RE₂O₃ into ceria and Raman spectroscopy is very much sensitive to oxygen polarizability and local coordination. Back scattered images collected on representative compositions support the above-mentioned results.     

Caught in the Hinact: Crystal Structure and Spectroscopy Reveal a Sulfur Bound to the Active Site of an O2‐stable State of [FeFe] Hydrogenase

[FeFe] hydrogenases are the most active H₂ converting catalysts in nature, but their extreme oxygen sensitivity limits their use in technological applications. The [FeFe] hydrogenases from sulfate reducing bacteria can be purified in an O₂‐stable state called H_inact. To date, the structure and mechanism of formation of H_inact remain unknown. Our 1.65 Å crystal structure of this state reveals a sulfur ligand bound to the open coordination site. Furthermore, in‐depth spectroscopic characterization by X‐ray absorption spectroscopy (XAS), nuclear resonance vibrational spectroscopy (NRVS), resonance Raman (RR) spectroscopy and infrared (IR) spectroscopy, together with hybrid quantum mechanical and molecular mechanical (QM/MM) calculations, provide detailed chemical insight into the H_inact state and its mechanism of formation. This may facilitate the design of O₂‐stable hydrogenases and molecular catalysts.     

Thin Coatings of α- and β-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light

Thin coatings of Bi₂O₃ were deposited on glass substrates by ultrasonic spray coating of THF solutions of the molecular precursor [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉] ⋅ 2DMSO ⋅ 7H₂O (OMc=O₂CC₃H₅) followed by hydrolysis and subsequent annealing. Depending on the synthetic protocol, the bismuth oxido cluster was transformed into either α- or β-Bi₂O₃. The as-synthesized Bi₂O₃ coatings were characterized by powder X-ray diffraction (PXRD), thickness measurements, diffuse reflectance UV-Vis spectroscopy (DRS), photoluminescence (PL) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The thin coatings (thickness: 5–16 μm) were compared with regard to their performance in photocatalytic rhodamine B (RhB) decomposition under visible light irradiation. The β-Bi₂O₃ coatings, that showed the highest photocatalytic activity, were used for the photocatalytic decomposition of other pollutants such as triclosan and ethinyl estradiol. In addition, the interplay between the photooxidation that is induced by the excitation of the catalyst using visible light and the photosensitized decomposition pathway was studied by degradation experiments of aqueous rhodamine B solutions using β-Bi₂O₃ coatings.     

Ordered Mesoporous Thin Films of Rutile TiO2 Nanocrystals Mixed with Amorphous Ta2O5

Ordered mesoporous thin films of composites of rutile TiO₂ nanocrystals with amorphous Ta₂O₅ are fabricated by evaporation‐induced self‐assembly followed by subsequent heat treatment beyond 780 °C. Incorporation of selected amounts of Ta₂O₅ (20 mol %) in the mesoporous TiO₂ film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block‐copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in‐depth composition analysis by X‐ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X‐ray absorption fine structure measurement on the composite film containing 20 mol % Ta₂O₅ and heated to 800 °C confirms the amorphous nature of the Ta₂O₅ phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light.     

硬模板法合成磁性石墨化介孔碳及在中药废水吸附处理中的应用

以SBA-15为模板, 蔗糖为碳源, 硝酸铁辅助催化合成磁性石墨化介孔碳复合材料(Fe/GMC). 利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)、N₂吸附-脱附(BET)、拉曼光谱等对反应产物进行了表征. 硝酸铁辅助催化可以在较低碳化温度(900℃)下实现介孔碳的部分石墨化, 并同步生成磁性Fe₃O₄颗粒, 合成的产物比表面积大、孔道有序、磁性强. 运用紫外-可见(UV-Vis)光谱考察了该复合材料对中药红花色素废水的吸附特性,复合材料的吸附速率快、吸附量高, 具有良好的脱色效果并能实现吸附剂的快速固液磁分离.     

常温常压下硅氨基化介孔SBA-15负载Keggin型钼钒杂多酸催化氧化乙醛的反应研究

Keggin-type molybdovanadophosphoric acids(HPA),H_4PMo_(11)VO_(40)(1),H_5PMo_(10)V_2O_(40)(2)and H_6PMo_9V_3O_(40)(3)were anchored onto γ-aminopropyltriethoxysilane(APTS)aminosilylated silica mesoporous SBA-15 throughacid-base neutralization and the resulting HPA/APTS/SBA-15 were characterized by BET,TEM,XRD,ICP,FTIRand ~(31)P MAS NMR.The characterization results indicate that the Keggin-structure of these HPAs is preservedwithin the mesoporous silica host.The samples were tested for catalytic aerobic oxidation of acetaldehyde hetero-geneously in liquid phase under ambient condition.The electrostatic force between heteropoly acid and aminogroups grafted on the silica channel surface leads to strong immobilization of HPA inside SBA-15 which is againstthe leaching during the reaction.The good catalytic performance and easy recycle of these catalysts make them aspotential environmental friendly catalysts for elimination of indoor air pollutants.     

Preparation and photocatalytic activity of magnetic samarium-doped mesoporous titanium dioxide at the decomposition of methylene blue under visible light

Preparation of samarium-doped mesoporous titanium dioxide (Sm/MTiO₂) coated magnetite (Fe₃O₄) photocatalysts (Sm/MTiO₂/Fe₃O₄) and their activities under visible light were reported. The catalysts with Sm/MTiO₂ shell and a Fe₃O₄ core were prepared by coating photoactive Sm/MTiO₂ onto a magnetic Fe₃O₄ core through the hydrolysis of tetrabutyltitanate (Ti(OBu)₄, TBT) with precursors of Sm(NO₃)₃ and TBT in the presence of Fe₃O₄ nanoparticles. The morphological, structural and optical properties of the prepared samples were characterized by BET surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of Sm ion content on the photocatalytic activity was studied. The photocatalytic activities of obtained photocatalysts under visible light were estimated by measuring the decomposition rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Sm/MTiO₂ was tightly bound to Fe₃O₄ and could be easily recovered from the medium by a simple magnetic process. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.     

Impact of the Pt catalyst on the oxygen electroreduction reaction kinetics on various carbon supports

Micro- and mesoporous carbide-derived carbons synthesized from molybdenum and tungsten carbides were used as porous supports for a platinum catalyst. Synthesized materials were compared with commercial Vulcan XC72R conducting furnace black. The scanning electron microscopy, X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and low-temperature N₂ adsorption methods were applied to characterize the structure of catalysts prepared. The kinetics of oxygen electroreduction in 0.5 M H₂SO₄ solution was studied using cyclic voltammetry and rotating disk electrode methods. The synthesized carbide-derived carbons exhibited high specific surface area and narrow pore size distribution. The platinum catalyst was deposited onto the surface of a carbon support in the form of nanoparticles or agglomerates of nanoparticles. Comparison of carbide-derived carbons and Vulcan XC72R as a support showed that the catalysts prepared using carbide-derived carbons are more active towards oxygen electroreduction. It was shown that the structure of the carbon support has a great influence on the activity of the catalyst towards oxygen electroreduction.     

A Direct and Rapid Route to Synthesize Pd/Si‐MCM‐41 at Room Temperature

The pure silica mesoporous molecular sieve MCM‐41 was synthesized under hydrothermal conditions. Pd/Si‐MCM‐41 was prepared by the incipient wetness impregnation of pure silica MCM‐41 with mixed solution of PdCl₂, ethanol and CH₂Cl₂. The samples were characterized by x‐ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms at 77 K. The XRD and TEM results reveal that Pd is actually anchored inside the pores of Si‐MCM‐41 and the Si‐MCM‐41 structure is clearly maintained after impregnation.     

Preparation and characterization of ZnTiO<Subscript>3</Subscript>–TiO<Subscript>2</Subscript>/pillared montmorillonite composite catalyst for enhanced photocatalytic activity

ZnTiO₃–TiO₂/organic pillared montmorillonite (pMt) composite catalyst was successfully prepared in this paper by immobilizing ZnTiO₃–TiO₂ onto pMt. The composition and texture of the prepared composite catalyst were characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive spectrometry, ultraviolet–visible light (UV–Vis) diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity was tested via photocatalytic degradation of methyl blue (MB) under both visible irradiation and UV light. The results indicated that the ZnTiO₃–TiO₂/pMt composite catalyst had an apparent absorption at the area of visible irradiation, and exhibited a higher efficiency of photocatalytic degredation of MB under visible irradiation. This was due to the heterostructure of ZnTiO₃–TiO₂, and the mesoporous structure and specific surface area of the ZnTiO₃–TiO₂/pMt composite. In addition, the results of the radical scavenging experiments showed that the holes and superoxide radicals are responsible for the degradation of MB under visible irradiation.     

Polyoxomolybdate‐Stabilized Ru0 Nanoparticles Deposited on Mesoporous Silica as Catalysts for Aromatic Hydrogenation

We use polyoxometalates as precursors for the preparation of heterogeneous catalysts. In the starting molecular precursor [{Ru(C₆Me₆)}₂Mo₅O₁₈{Ru(C₆Me₆)(H₂O)}], three ruthenium arene fragments are supported on a formally lacunary Lindqvist‐type polyoxomolybdate. This species was introduced by incipient wetness impregnation into the porosity of a SBA‐15‐type mesoporous silica. The evolution of the system under reducing atmosphere is followed by several methods, such as temperature‐programmed reduction (TPR), Raman, and X‐ray absorption spectroscopy (XAS). The results indicate that the polyoxometalate structure is retained after grafting on silica and allows the stabilization of Ru⁰ nanoparticles after reduction. The resulting system exhibits interesting catalytic activity in benzene hydrogenation.     

In Situ and Post Reaction Cobalt-Incorporation into Periodic Mesoporous Ethanesilica Materials

Cobalt incorporated periodic mesoporous organosilica materials were synthesized in situ by condensation of 1,2-bistrimethoxysilylethane (BTME) in the presence of cetyltrimethylammonium bromide (CTAB) and cobalt nitrate and by incipient wetness addition of Co to BTME mesoporous silica. BET and pore measurements as well as DTA and TGA analysis of the materials revealed that the mesoporous structure is retained under the synthetic conditions used, after solvent extraction and importantly to temperatures of ca. 400°C under N₂. Raman spectroscopy also revealed the presence of the ethane moiety in the Co materials and that the surfactant was removed by solvent extraction. BET and pore measurement studies revealed that the surface area and pore volume of the materials decreased with increasing cobalt loading. The studies indicate that the new Co materials have potential as Fischer-Tropsch catalysts.     

Polymer immobilized Fe(III) complex of 2-phenylbenzimidazole: An efficient catalyst for photodegradation of dyes under UV/Visible light irradiation

Fe(III) complex of 2-phenylbenzimidazole has been covalently anchored on polymer and characterized by elemental analysis, FT-IR, far-IR, BET surface area measurements, UV–Vis/DRS spectroscopy, thermo-gravimetric analysis and magnetic moment measurements by VSM which confirmed an octahedral environment around Fe(III) in the bound complex. The photocatalytic performance of this complex was evaluated in the photodegradation of dyes in presence of H₂O₂ as an oxidizing agent. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as pH, oxidants, concentration of dye, H₂O₂ and catalyst for the maximum degradation of dye. The photodegradation was found to be 100% with complete mineralization in 150?min. The comparison of photocatalytic efficiency of the catalyst under visible light, sunlight and dark conditions are accomplished. Comparison between catalytic activity of the polymer-supported complex and unbound complex demonstrated that the polymer-supported complex was more active. Photocatalytic performance of PS-Fe(III)PBMZL was also compared with commercial TiO₂ (P25). This heterogeneous complex retained its activity up to 8 runs. A tentative mechanism has been proposed.     

Plasma-Catalytic Oxidation of Toluene on MnxOy at Atmospheric Pressure and Room Temperature

Mn_xO_y/SBA-15 catalysts were prepared via the impregnation method and utilized for toluene removal in dielectric barrier discharge plasma at atmospheric pressure and room temperature. The catalysts were characterized by X-ray diffraction, N₂ adsorption–desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, H₂ temperature-programmed reduction, and O₂ temperature-programmed desorption methods. The characterization results indicated that manganese loading did not influence the 2D-hexagonal mesoporous structure of SBA-15. The catalyst had various oxidation states of manganese (Mn²⁺, Mn³⁺, and Mn⁴⁺), with Mn³⁺ being the dominant oxidation state. Toluene removal was investigated in the environment of pure N₂ and 80 % N₂ + 20 % O₂ plasma, showing that the toluene removal efficiency and CO₂ selectivity were noticeably increased by Mn_xO_y/SBA-15, especially in the presence of 5 % Mn/SBA-15. This activity was closely related to the high dispersion of 5 % Mn on SBA-15 and the lowest reduction temperature exhibited by this catalyst. Mn loading increased the yield of CO₂ in the N₂ plasma and promoted the deep oxidation of toluene. During toluene oxidation, oxygen exchange might follow a pathway, wherein bulk oxygen was released from the Mn_xO_y/SBA-15 surface; gas-phase O₂ subsequently filled up the vacancies created on the oxide. Each of the manganese oxidation states played an important role; Mn₂O₃ was considered as a bridge for oxygen exchange between the gas phase and the catalyst, and Mn₃O₄ mediated transfer of oxygen between the catalyst and toluene.     

Mesoporous SBA-15 materials modified with PW or W active species as catalysts for the epoxidation of olefins with H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Five catalysts containing PW or W active species that anchored onto aminosilylated mesoporous silica SBA-15 by a post-grafting route were prepared and the resulting PW or W/APTES/SBA-15 hybrid materials were characterized by XRD, N₂ adsorption/desorption, surface area analysis, TEM, FT-IR, and ICP (inductively coupled plasma atomic emission spectroscopy). The names of these catalysts have been abbreviated as SBA-15m-a, SBA-15m-b, SBA-15m-c, SBA-15m-d, and SBA-15m-e according to the different active species. The PW or W active species were highly dispersed in the channels of the modified mesoporous materials. The interaction between PW or W species and amino groups grafted on the channel surface of SBA-15 led to the immobilization of PW or W species. Their catalytic activity in the epoxidation of cyclooctene with H₂O₂ as oxidant was investigated. Among them, SBA-15m-a showed the best performance, with 98.9% conversion and 98.4% selectivity. The catalyst could be reused for six times with a little decrease in activity.