Z型异质结Cu2O/Bi2MoO6的构建及光催化降解性能

通过水热法制备出一系列Z型异质结Cu₂O/Bi₂MoO₆新型光催化剂。采用扫描电子显微镜、粉末X射线衍射、红外光谱、紫外可见吸收光谱等表征手段研究了催化剂的形貌、结构性质和光电化学性质,并以四环素(TC)为降解目标污染物,进一步探究了其催化效率。实验结果表明,Cu₂O的加入提高了复合催化剂的光催化性能,其中20% Cu₂O/Bi₂MoO₆复合催化剂(Cu₂O和Bi₂MoO₆的质量比为20%)降解效果最好,100 min内可降解95%的TC。Cu₂O与Bi₂MoO₆之间的协同作用使其可以吸收更多的可见光,所构建的Z型异质结改变了电子转移途径,提高了电子与空穴的分离效率,光催化活性显著提高。通过自由基捕获实验和能带结构,分析了Z型异质结Cu₂O/Bi₂MoO₆复合催化剂光催化降解TC可能的机理。     

静电自组装制备纳米TiO2/SiO2光催化材料

采用静电自组装方法制备了纳米TiO2/SiO2光催化材料。采用巯丙基三甲氧基硅烷偶联剂对SiO2进行干法改性,采用双氧水/冰醋酸将偶联剂巯基基团氧化为磺酸基基团。在正负电荷的吸引下,带负电荷的SiO2与带正电荷的钛聚合阳离子自发地组装在一起,经一定温度热处理得到纳米TiO2/SiO2光催化材料。采用XRD、FTIR、PL、UV-Vis DRS、SEM和ICP等对材料进行了分析和表征。采用甲基橙溶液评价材料的光催化性能。结果表明:SiO2促使锐钛矿的形成,抑制锐钛矿向金红石的转变,减小TiO2的晶粒尺寸,使得TiO2光吸收波长发生蓝移。TiO2与SiO2通过Si-O-Ti键发生结合。采用静电自组装方法制备的材料中TiO2的含量高于传统方法,导致材料的光催化性能有所提高。     

Synthesis of big palladium clusters. Preparation of Pd23(CO)20(PEt3)8

Selective methods for the synthesis of the cluster Pd₂₃(CO)₂₀L₈, L=PEt₃, have been suggested. The compound has been prepared by two routes: by the reaction of Pd₁₀(CO)₁₂L₆ with Me₃NO in the presence of HOAc with removal of CO from the gas phase, and by the reaction of Pd₁₀(CO)₁₂L₆ with Pd(OAc)₂ and CO followed by oxidation by Me₃NO in an inert atmosphere.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1299–1300, July, 1993.     

Base-catalyzed reactions enhanced by solid acids: Amine-catalyzed nitroaldol (Henry) reactions enhanced by silica gel or mesoporous silica SBA-15

The reactions of various aldehydes with CH₃NO₂ catalyzed by Et₃N, n-C₆H₁₃NH₂, and Me₂N(CH₂)₂NH₂ were accelerated by the addition of silica gel to give aromatic (aliphatic) β-nitroalcohols, aromatic nitroalkenes, and aromatic 1,3-dinitroalkanes, respectively. Mesoporous silica SBA-15 showed higher activity than silica gel for the synthesis of aromatic nitroalkenes by the reactions of the corresponding aldehydes with CH₃NO₂ catalyzed by n-C₆H₁₃NH₂.     

Pt/g-C3N4/KB纳米复合催化剂的制备及其甲醇氧化性能

采用溶液中等离子放电法制备出了Pt纳米颗粒,用热氧化刻蚀和水热法成功的对石墨相氮化碳（g-C₃N₄）进行处理进而均匀吸附在科琴黑（KB）表面,最终制备出了Pt/g-C₃N₄/KB纳米复合催化剂。通过XRD分析,扫描电镜,透射电镜和电化学工作站探究了催化剂的组成、结构、颗粒大小以及电化学性能。Pt/g-C₃N₄/KB纳米复合催化剂展现出了良好的甲醇电氧化性能,性能的提升可能是由于g-C₃N₄良好的化学稳定性,N元素的存在改变Pt外层电子结构从而提高催化活性,这些因素提高了Pt的催化效率。     

尖晶石型LiMn2-xInxO4(x=0，0.01，0.02，0.05)的合成及电化学性能研究

以醋酸锰、氢氧化锂和三氧化二铟为原料,以柠檬酸为配位剂,采用溶胶-凝胶法制备了掺杂In的尖晶石LiMn2-xInxO4(x=0,0.01,0.02,0.05),采用XRD、SEM对目标材料进行了结构和形貌表征,采用恒流充放电、循环伏安(CV)以及交流阻抗(EIS)谱测试对材料进行了电化学性能表征,考察了不同In掺杂量对材料性能的影响。结果表明,当In掺杂量为1%时,LiMn1.99In0.01O4样品具有纯的尖晶石锰酸锂结构,在0.5C和3.4～4.35 V电压范围条件下,LiMn1.99In0.01O4的初始放电容量为119.9 mAh.g-1,经过1C 30次,2C 30次,再0.5C 5次循环后,其放电容量保持率为84.9%,显示了良好的电化学性能。掺杂1%的In的样品比未掺杂的样品具有更优的高温循环稳定性能。     

Intramolecular π–π Interactions in Flexibly Linked Partially Fluorinated Bisarenes in the Gas Phase

Three compounds with phenyl and pentafluorophenyl rings bridged by (CH₂)₃ and (CH₂)₂SiMe₂ units were synthesized by hydrosilylation and C−C coupling reactions. Their solid‐state structures are dominated by intermolecular π stacking interactions, primarily leading to dimeric or chain‐type aggregates. Analysis of free molecules in the gas phase by electron diffraction revealed the most abundant conformer to be significantly stabilized by intramolecular π–π interactions. For the silicon compounds, structures characterized by σ–π interactions between methyl and pentafluorophenyl groups are second lowest in energy and cannot be excluded completely by the gas electron diffraction experiments. C₆H₅(CH₂)₃C₆F₅, in contrast, is present as a single conformer. The gas‐phase structures served as a reference for the evaluation of a series of (dispersion‐corrected) quantum‐chemical calculations.     

Shock‐Tube Experiments and Kinetic Modeling of CH3NHCH3 Ignition at Elevated Pressures

Ignition delay times of CH₃NHCH₃/O₂/Ar mixtures are measured with a shock tube in the temperature range of 1040–1604 K. Different pressures (4, 8, and 18 atm) and equivalence ratios (0.5, 1, and 2) are investigated. A recently developed CH₃NHCH₃ kinetic model is examined, and then modified by adding the hydrogen abstractions from CH₃NHCH₃ by HO₂ and NO₂. The rate constants of the hydrogen abstraction by HO₂ are estimated by analogy to the CH₃OH + HO₂ system, and those of the hydrogen abstraction by NO₂ by analogy to the CH₃NH₂ + HO₂ system. The modified model is well validated against the present measurements. Based on this model, sensitivity analysis and reaction pathway analysis are performed to provide insight into the chemical kinetics of CH₃NHCH₃ ignition. CH₃NHCH₃ is mainly consumed by hydrogen abstractions at low temperatures, and its unimolecular decomposition becomes important at higher temperatures.     

Gd4I6CN: Ein Carbidnitrid mit Ketten aus Gd6(C2)-Oktaedern und Gd6N2-Tetraederdoppeln

Gd₄I₆CN: A Carbide Nitride with Chains of Gd₆(C₂) Octahedra and Gd₆N₂ Double Tetrahedra The compound α-Gd₄I₆CN is prepared by reaction of Gd, GdI₃, C, and GdN (1:2:1:1 mole ratio) at 1 170 K in sealed Ta tubes. It is obtained as brown red, transparent needles which are air and moisture sensitive. The structure of α-Gd₄I₆CN contains Gd₆ octahedra centered by C₂ groups and double tetrahedra centered by N atoms. The units are alternatingly connected via common edges to form chains (Gd₂Gd_4/2C₂) (Gd_2/2Gd_2/2N)₂ parallel [001]. The linear chains are surrounded by I atoms above all free edges of the metal polyhedra and linked according to (Gd₂Gd_4/2C₂) (Gd₂Gd_4/2N₂)I_4/2I₈I₂ in the a – b plane. We also found β-Gd₄I₆CN, which is formed in a monotropic transition from the α-form. In the structure the chains of Gd octahedra and tetrahedra as described for α-Gd₄I₆CN are more densely packed. The structure of Y₆I₉C₂N is composed by chains of pairs of Y-octahedra and Y-tetrahedra, respectively. The octahedra are centered by C₂ groups, the tetrahedra by N-atoms. We also synthesized the compounds Gd₄Br₆CN und La₄I₆CN by tempering at 1 220 K. They are isotypic with α-Gd₄I₆CN.     

K3FeSe3 und K3Fe2Se4, zwei neue Verbindungen im System K/Fe/Se

K₃FeSe₃ and K₃Fe₂Se₄, Two New Compounds in the System K/Fe/Se The two selenides K₃FeSe₃ and K₃Fe₂Se₄ were synthesised by fusion reactions of potassium carbonate with iron and selenium in a stream of hydrogen charged with selenium at 695 °C and 710–730 °C, respectively. The crystal structures were determined by single‐crystal X‐ray diffractometer data. The atomic arrangement of K₃FeSe₃ is characterised by edge sharing [Fe₂Se₆] double tetrahedra separated by potassium ions (space group P2₁/c, Z = 4). The characteristic structural unit of the mixed‐valent compound K₃Fe₂Se₄ is a zig‐zag chain of edge‐sharing, iron‐centred selenium tetrahedra, again separated by potassium ions (space group Pnma, Z = 4).     

Synthesis and characterization of a new nanomagnetic coordination composite from Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Cu(II) complex: as an efficient catalyst in oxidation of benzyl alcohol

New nanomagnetic coordination compound, Cu(salal)@DA@ Fe₃O₄, was synthesized by bonding between the Cu(II) complex and Fe₃O₄ nanoparticles. The Cu complex has two aldehyde groups. The surface of Fe₃O₄ nanoparticles was modified by the dopamine molecules and the amine group of dopamine is free. Therefore, the Cu complex is covalently anchored to Fe₃O₄ nanoparticle by the formation of imine bonds between the aldehyde and amine groups. On the other hand, a Cu-Schiff base complex is immobilized on nano-Fe₃O₄ by dopamine as a bridge. Consequently, the homogeneous Cu complex is easily converted to the heterogeneous-magnetic compound in this project. The Cu complex, Fe₃O₄ and new nanocomposite were characterized by general techniques such as FTIR, TGA, XRD, FESEM, MAP and EDS. The average crystallite size of Fe₃O₄ and Cu(salal)@DA@ Fe₃O₄ were calculated by Scherrer’s formula and they are 18.52 and 24.69 nm, respectively. These results indicated the average crystallite size of Fe₃O₄ nanomaterials is slightly increased by surface modification by Cu complex. The FESEM images show a tiny spherical mushroom morphology for both nanocompounds, and the EDS analysis confirms the presence of Fe, Cu, C and O in the nanomagnetic coordination composite. The catalytic properties of these compounds were studied and compared to oxidation of benzyl alcohol by 30% H₂O₂ at room temperature. The results show that the catalytic properties Cu complex and Fe₃O₄ were enhanced by cooperation of both compounds in a nanocoordination composite.     

Pt/g-C_3N_4/KB纳米复合催化剂的制备及其甲醇氧化性能

采用溶液中等离子放电法制备出了Pt纳米颗粒,用热氧化刻蚀和水热法成功的对石墨相氮化碳(g-C_3N_4)进行处理进而均匀吸附在科琴黑(KB)表面,最终制备出了Pt/g-C_3N_4/KB纳米复合催化剂。通过XRD分析,扫描电镜,透射电镜和电化学工作站探究了催化剂的组成、结构、颗粒大小以及电化学性能。Pt/g-C_3N_4/KB纳米复合催化剂展现出了良好的甲醇电氧化性能,性能的提升可能是由于g-C_3N_4良好的化学稳定性,N元素的存在改变Pt外层电子结构从而提高催化活性,这些因素提高了Pt的催化效率。     

沉淀方法对铜基甲醇合成催化剂前驱体及其性能的影响

 分别采用共沉淀法 (CP)、两步沉淀法 (TP) 和分步沉淀法 (FP) 制备了 Cu/ZnO/Al₂O₃ 甲醇合成催化剂. 结果发现, FP 催化剂上甲醇收率比 CP 催化剂上高 46.3%, 比 TP 催化剂上高 9.3%. 采用 X 射线衍射、微分热重分析、红外光谱、N₂ 吸附-脱附、程序升温还原及 N₂O 滴定等方法表征了催化剂. 结果表明, FP 催化剂前驱体中 (Cu,Zn)₂CO₃(OH)₂ 和 (Zn,Cu)₅(CO₃)₂(OH)₆ 两种高活性物相较多, 而 (Cu,Zn)₆Al₂(OH)₁₆CO₃•4H₂O 物相较少, 焙烧后形成了较多的 CuO-ZnO 固溶体, 同时形成了较多的碳酸盐, 因而催化活性更高.     

Oxazine750对平行四股螺旋结构的识别与稳定作用

以d[TG₄T]₄、d[G₄T₄G₄]₂和c-myc序列为代表,采用竞争平衡透析、紫外光谱和圆二色光谱研究了oxazine750对四股螺旋结构的识别与稳定作用。 结果表明,oxazine750能够更好的结合在平行四股螺旋上,而对反平行四股螺旋结合较少。 热变性实验表明,oxazine750使d[TG₄T]₄形成的平行结构的四股螺旋的解旋温度提高了11 ℃,对c-myc形成的平行四股螺旋的解旋温度甚至提高了40 ℃。 而对d[G₄T₄G₄]₂形成的反平行结构解旋温度降低了近8 ℃。     

碱金属助剂类型及前驱物对改性NiAl复合氧化物催化分解N2O活性的影响

制备了不同Ni/Al原子比的NiAl类水滑石样品,焙烧获得NiAl复合氧化物,用于N₂O分解反应,研究了NiAl复合氧化物组成对催化活性的影响。在活性较高的NiAl复合氧化物表面浸渍碱金属碳酸盐溶液,制备改性NiAl复合氧化物,考察了碱金属类型（Na、K、Cs）和钾前驱物（K₂CO₃、K₂C₂O₄、CH₃COOK、KNO₃）对改性催化剂活性的影响。用XRD、ICP-AES、FT-IR、BET、H₂-TPR、XPS技术表征了催化剂的组成结构。结果表明,Ni/Al原子比为2.7的NiAl复合氧化物催化活性较高;Na、K、Cs碳酸盐改性NiAl复合氧化物均提高了催化剂活性,其中K的助剂效应最强。钾前驱物对K改性NiAl复合氧化物的催化活性有显著影响,其中碳酸钾、醋酸钾、草酸钾的加入明显提高了改性催化剂的催化活性,而加入硝酸钾反而降低了催化剂活性。     

Two-Dimensional Sol-Gel Synthesis of Ultrathin Zirconia and Hetero-Layered Titania/Zirconia Films

Synthesis of ZrO₂ and hetero-layered TiO₂/ZrO₂ ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C₁₈AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C₁₈AA was spread on the water surface, Zr-based gel films stabilized with C₁₈AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO₂ ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C₁₈AA]. Well-organized hetero-multilayers composed of ultrathin TiO₂ and ZrO₂ layers could be fabricated by the alternate deposition of C₁₈AA-stabilized Ti- and Zr-gel films.     

Synthesis and x-ray crystal structure of the TiMgCl5(OOCCH2Cl) · (ClCH2COOC2H5)3 Adduct

The synthesis of the TiMgCl₅(OOCCH₂Cl) · (ClCH₂COOC₂H₅)₃ adduct, obtained by reacting TiCl₄ with a solution of MgCl₂ in dry ClCH₂COOC₂H₅, is reported together with its molecular and crystal structure as determined by x-ray diffraction. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.057 for 1318 independent observed reflections. Crystals are monoclinic, space-group P2₁/c, with 4 formula units in a unit-cell of dimensions a = 10.480(4), b = 19.641(9), c = 16.597(6) Å, β = 120.21(5)°. The titanium(IV) atom is octahedrally coordinated by five chlorine atoms and an oxygen atom of a OOCCH₂Cl residue. The magnesium atom is similarly coordinated by two chlorine atoms, the carbonyl oxygen atoms of three ClCH₂COOC₂H₅ molecules and an oxygen atom of the OOCCH₂Cl residue. The two octahedra share an edge by a double chlorine bridge between the magnesium and the titanium atoms and are also connected by the COO group of the OOCCH₂Cl residue. Changes in the configurations and dimensions with respect to the free acceptor and donor molecules are discussed.     

Semi-Continuous Heterophase Polymerization to Synthesize Nanocomposites of Poly(acrylic acid)-Functionalized Carbon Nanotubes

Two materials, pure poly(acrylic acid) (PAA) and nanocomposites with a matrix of PAA and carbon nanotubes (CNTs) as reinforcing agent were synthesized by semi-continuous heterophase polymerization (SHP). CNTs were prepared by a chemical vapor deposition technique and purified by steam. CNTs were characterized by a high resolution scanning electron microscopy (HRSEM) and Raman and Fourier transform infrared spectroscopies. Nanocomposites were prepared with: (i) purified CNTs (CNTs_p) or (ii) purified and functionalized CNTs possessing an acyl chloride moiety (CNTs_OCl). In both cases, the nanocomposites synthesis was carried out by in situ polymerization of acrylic acid (AA) by SHP. When CNTs_OCl were used previously to the polymerization of AA, a series of specific amounts of CNTs_OCl and AA were mixed to induce a chemical reaction between the carboxyl group of AA and the acyl chloride group of the CNTs_OCl. The product, acrylic acid grafted to CNTs_OCl (CNTs_OCl-AA), was used to prepare the PAA-CNTs_OCl nanocomposites. The PAA-CNTs_OCl nanocomposites were characterized by HRSEM, Raman, FTIR and CPMAS ¹³C-NMR spectroscopies and also by thermogravimetric analysis (TGA). The results reveal that PAA-CNTs_OCl nanocomposites were formed by PAA macromolecules grafted to CNTs_OCl. The kinetic behavior observed for the synthesis of pure PAA or PAA-CNTs_OCl nanocomposites by SHP was similar. Latexes of PAA-CNTs_OCl nanocomposites were stable without formation of a precipitate of CNTs_OCl for over 1.5 years, while latex prepared with CNTs_p and PAA, was unstable and formation of a precipitate of CNTs_p was observed immediately after its preparation. PAA-CNTs_p nanocomposites were characterized only by TGA. Moreover, latex of the PAA-CNTs_p nanocomposite that did not precipitate immediately after its preparation, turned into a gel; this gelation never occurred with the PAA-CNTs_OCl nanocomposite latex.     

Characterization of some new alkali metal molybdate hydrates by thermal and X-ray methods

Preparation and characterization of four new hydrated alkali metal molybdates Na₂Mo₄O₁₃·6H₂O, K₂Mo₄O₁₃·3H₂O, Rb₂Mo₄O₁₃·2H₂O and Cs₂Mo₄O₁₃·2H₂O are described. The compounds were prepared by crystallizing the solution obtained by dissolving MoO₃ and corresponding alkali metal carbonates A₂CO₃ or molybdate A₂MoO₄ in stoichiometric amount in distilled water. The hydrated molybdates were characterized by thermal (TG/DTA) and X-ray diffraction (XRD) methods. The number of water molecules in the compounds were determined from their TG /DTA curves recorded in air and identification of their dehydration products was done by XRD. The cell parameters of the compounds were obtained by indexing their XRD patterns. Attempt to prepare the corresponding hydrated compound of lithium was not successful. This revised version was published online in July 2006 with corrections to the Cover Date.     

球形Bi_4Ti_3O_(12)制备及其可见光催化性能

采用水热法合成球形钛酸铋复合氧化物光催化剂,利用SEM、XRD和UV-Vis DRS等表征手段对复合氧化物的晶体结构、微观形貌和光学性能进行了分析,结果表明,制备的钛酸铋复合氧化物为10 nm的球形颗粒,具有良好的晶型结构,禁带宽度为2.7 nm,有较好的可见光吸收能力。以亚甲基蓝、甲基橙及酸性品红为目标污染物,研究了复合氧化物在可见光下的光催化降解有机污染物的性能,并对光催化降解机理进行了探讨。结果表明,在可见光照射下,该复合氧化物对酸性品红降解效果明显优于亚甲基蓝和甲基橙,光照150 min下,降解率可达91%。