介孔TiO2-SO2-4的合成及表征

在不使用有机模板剂的条件下,以工业硫酸钛溶液为原料合成了高热稳定的锐钛矿型介孔TiO2-SO2-4. 用X射线衍射、N2吸附、扫描电镜、X射线能谱、傅里叶变换红外光谱和紫外-可见光谱对样品进行了表征,并考察了其光催化性能. 结果表明,硫酸根在焙烧过程中与前驱体介孔偏钛酸孔壁上自由羟基的键合起到了孔结构导向及支撑作用, 500 ℃焙烧后样品仍具有202.2 m2/g的比表面积及2.8 nm的平均孔径. 焙烧产物TiO2-SO2-4中 S = O 的强电子诱导效应不仅使邻近的Ti成为超强酸中心,还使二氧化钛的吸收光谱产生30 nm的红移,光催化活性显著提高.     

Si掺杂介孔SO2-4/TiO2的非模板剂法合成及表征

在不使用模板剂的条件下,以工业硫酸氧钛溶液为原料合成介孔偏钛酸前驱体,再经正硅酸乙酯浸渍焙烧制备了具有良好热稳定性的Si掺杂介孔SO2-4/TiO2.采用X射线衍射、N2吸附-脱附、扫描电镜、X射线能谱和傅里叶变换红外光谱等表征方法对样品的组成和结构进行了分析,并考察了该材料在亚甲基蓝氧化降解反应中的光催化性能.结果表明,在焙烧过程中,被吸附在偏钛酸孔道内的正硅酸乙酯发生水解,并与偏钛酸孔壁上的自由羟基形成 Ti - O - Si 键;Si进入二氧化钛骨架中,对孔结构起到了支撑作用,从而提高了介孔SO2-4/TiO2的热稳定性.700 ℃焙烧 2 h 后,Si掺杂介孔SO2-4/TiO2材料的比表面积仍达到189 m2/g,平均孔径为2.8 nm.400 ℃焙烧的样品在亚甲基蓝降解反应中表现出较好的光催化活性.     

Si掺杂介孔SO_4~(2-)/TiO_2的非模板剂法合成及表征

在不使用模板剂的条件下,以工业硫酸氧钛溶液为原料合成介孔偏钛酸前驱体,再经正硅酸乙酯浸渍焙烧制备了具有良好热稳定性的Si掺杂介孔SO42-/TiO2.采用X射线衍射、N2吸附-脱附、扫描电镜、X射线能谱和傅里叶变换红外光谱等表征方法对样品的组成和结构进行了分析,并考察了该材料在亚甲基蓝氧化降解反应中的光催化性能.结果表明,在焙烧过程中,被吸附在偏钛酸孔道内的正硅酸乙酯发生水解,并与偏钛酸孔壁上的自由羟基形成Ti-O-Si键;Si进入二氧化钛骨架中,对孔结构起到了支撑作用,从而提高了介孔SO42-/TiO2的热稳定性.700℃焙烧2 h后,Si掺杂介孔SO42-/TiO2材料的比表面积仍达到189 m2/g,平均孔径为2.8 nm.400℃焙烧的样品在亚甲基蓝降解反应中表现出较好的光催化活性.     

低温苯甲醇醇解法制备高活性锐钛矿型纳米晶TiO2光催化剂

 以TiCl4 为钛源,采用低温苯甲醇醇解法制备了不同粒径及晶相组成的大表面TiO2纳米晶,利用X射线衍射、热重-差热分析、透射电子显微镜、拉曼光谱、紫外-可见漫反射光谱和N2物理吸附等方法考察了焙烧温度和焙烧时间对其晶相组成、晶粒尺寸、比表面积及孔体积等微结构性质的影响,并以苯酚的光催化降解为模型反应评价了样品的光催化活性. 结果表明,未经任何热处理的TiO2样品即为锐钛矿晶相,控制焙烧温度及焙烧时间可进一步调控样品的粒径、比表面积、晶相结构及表面氧缺位浓度. 经400 ℃焙烧3 h制备的纳米晶TiO2具有最佳的光催化活性,其活性比商用Degussa P-25 TiO2更高.     

生物质C-N-P自掺杂TiO_2的合成及其对亚甲基兰的光催化降解活性

采用溶胶-超声辐照技术同步合成了生物质C-N-P自掺杂TiO_2复合催化剂,通过X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电子显微镜(FESEM)、紫外-可见漫反射光谱(UV-Vis-DRS)及光致发光光谱(PL)对样品进行了表征.以亚甲基兰(MB)为目标污染物,研究了C-N-P共掺杂TiO_2的可见光光催化性能.实验结果表明,在可见光照射下,光催化反应时间为2 h时,C-N-P共掺杂TiO_2复合催化剂对亚甲基兰的降解效率最高可达9 8.5%;相比纯TiO_2,C-N-P共掺杂TiO_2复合催化剂的比表面积增大,吸收边带红移,禁带宽度减小,相变温度升高,光生载流子复合率降低.     

介孔AgBr/TiO_2-SiO_2光催化剂的制备及其可见光催化活性

通过沉积法将光活性AgBr半导体负载到介孔TiO_2-SiO_2载体上合成了新型的AgBr/TiO_2-SiO_2复合光催化剂.采用X射线衍射仪、高分辨透射电镜、紫外-可见吸收光谱仪等分析了AgBr/TiO_2-SiO_2复合光催化剂的结构和光谱性质;并采用BET法测定了样品的比表面积和孔分布.结果表明,介孔TiO_2-SiO_2载体的比表面积为135.5m2/g,平均孔径约为3.8nm,AgBr的负载可以有效地将AgBr/TiO_2-SiO_2复合光催化剂的吸收光谱从紫外光区扩展到可见光区,且AgBr和TiO_2形成了异质结结构,强化了AgBr与介孔TiO_2-SiO_2载体的协同作用.以罗丹明B作为探针分子,评价了AgBr负载量对复合光催化剂可见光催化活性的影响.结果发现,当AgBr∶TiO_2=0.1,0.2,0.3和0.4(物质的量之比,下同)时,复合光催化剂的光催化反应速率常数分别为0.008 5、0.028 6、0.024 6和0.019 3min-1,活性先增加后减小,当AgBr∶TiO_2=0.2时,复合光催化剂表现出最高的光催化活性,并且在5次循环测试中均表现出较高的光催化活性.     

钯氮共掺杂TiO2的制备与表征及其可见光催化活性

在空气气氛和N₂中热处理表面均匀分散有尿素和氯化钯的纳米管钛酸,制备了两个系列Pd/N共掺杂的TiO₂光催化剂,并对所得样品进行了X射线衍射、透射电镜、X射线光电子能谱、紫外-可见漫反射光谱、荧光光谱和电子自旋共振等表征.结果表明,焙烧气氛对样品的形貌、晶体结构、光谱吸收、生成的氧空位浓度和可见光光催化性能的影响很大,其中在空气气氛中制备的样品光催化性能优于在N₂中制备的样品.在可见光(λ≥420nm)照射下,以丙烯为模型污染物考察了样品的光催化活性,发现在空气中400℃下焙烧的样品具有最佳的可见光催化活性.另外,讨论了Pd/N共掺杂TiO₂光催化剂具有可见光响应的机理,认为掺杂的Pd/N元素和制备过程中生成的氧空位是影响可见光催化性能的重要因素.     

添加NaBF_4对阳极氧化法制备TiO_2纳米管光催化剂的影响

在阳极氧化电解液中添加Na BF4制得了具可见光活性的B掺杂TiO_2纳米管阵列(B/TNTs)。采用扫描电镜(FE-SEM)、能谱仪(EDS)、X射线衍射(XRD)、傅立叶红外光谱(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)以及X射线光电子能谱(XPS)对样品进行表征,以亚甲基蓝(MB)的光催化降解为目标反应评价其光催化活性。结果表明:添加Na BF4后,TiO_2纳米管表面形貌变化较大;B掺入到TiO_2晶格中形成B-O-Ti键;B掺杂使得TiO_2纳米管表面羟基量增加、光学带隙能减小、光吸收阀值红移,且B掺杂量越多,其相应值的变化量越大;B掺杂能促进TiO_2锐钛矿相的发育,纳米管经550℃煅烧后仍保持未掺杂样品的锐钛矿相结构;Na BF4的最佳添加量为0.6%(w/w)时,所得样品光催化活性最佳,可见光下光催化降解MB的4 h降解率由未添加的39.90%提高至75.15%,且反复使用10次后其光催化性能基本保持不变;总有机碳(TOC)分析结果表明,MB在可见光下能被B/TiO_2有效矿化。     

Eu~(3+)掺杂NaBi(MoO_4)_2/TiO_2复合纤维制备及其光裂解水制氢

以电纺TiO_2纳米纤维为基质,利用水热法制备了异质结型Eu~(3+)掺杂NaBi(MoO_4)_2/TiO_2复合纤维。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、 X射线光电子能谱(XPS)、高分辨透射电镜(TEM)、紫外-可见漫反射(UV-Vis DRS)光谱以及荧光(PL)光谱等分析测试手段对样品的物相、形貌和光学性能等进行表征。以三乙醇胺为电子给体,研究了Eu~(3+)掺杂NaBi(MoO_4)_2/TiO_2复合纤维光催化裂解水制氢的反应过程。结果表明:NaBi(MoO_4)_2与TiO_2复合形成异质结,使光生电子-空穴对得到较好分离,而Eu~(3+)掺杂进入NaBi(MoO_4)_2晶格,部分取代Bi~(3+)离子,导致晶胞膨胀,在拓宽光谱响应范围的同时,形成光生载流子的浅势捕获阱,进一步促进了光生电荷的产生、转移,有效提高材料的光催化制氢活性。最佳产氢速率达到7.86 mmol·h~(-1)·g~(-1)。     

以花瓣为模板制备TiO2分层介孔纳米片

以月季花花瓣为模板, 经钛盐溶液浸渍后煅烧, 合成了新型TiO2 分层介孔纳米片. 采用X射线衍射(XRD)、 场发射扫描电子显微镜(FESEM)、 环境扫描电子显微镜(ESEM)、 透射电子显微镜(TEM)、 紫外-可见漫反射光谱(UV-Vis/DRS)和氮气吸附-脱附曲线分析等手段对样品进行了表征. 结果表明, 所得样品由厚度约4 nm的具有生物形态结构的锐钛矿型TiO2 纳米片组成. TiO2 薄层表面存在大量介孔, 其孔径集中分布于4 nm左右. 由紫外-可见漫反射吸收光谱可知, 材料的吸收边较纳米TiO2 (P25)红移了约20 nm, 因而具有更高的可见光光催化活性. TiO2 分层介孔纳米片在阳光下表现出较强的光催化活性, 在90 min内对亚甲基蓝的降解率可达98%, 远高于TiO2 纳米粉.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Thermal decomposition of Me3SnO2PCl2, Me2Sn(O2PCl2)2 and Ph3SnO2PCl2

TG and DTA studies on Me₃SnO₂PCl₂, Me₂Sn(O₂PCl₂)₂ and Ph₃SnO₂PCl₂ were carried out under dynamic argon atmosphere. The results show that the decomposition proceeds in different stages leading to the formation of Sn₃(PO₄)₂ as a stable product. This compound was characterized by IR spectroscopy. Decomposition schemes involving reductive elimination reactions were proposed.     

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.