Assembly of ϵ-Keggin Polyoxometalate from Molecular Crystal to Zeolitic Octahedral Metal Oxide

Zeolitic octahedral metal oxides are inorganic crystalline microporous materials with adsorption and redox properties. New ϵ-Keggin nickel molybdate–based zeolitic octahedral metal oxides have been synthesized. ³¹P NMR spectroscopy shows that reduction of Mo^VI-based molybdates forms an ϵ-Keggin polyoxometalate that immediately transfers to the solid phase. Investigation of the formation process indicates that a low Ni concentration, insoluble reducing agent, and long synthesis time are the critical factors for obtaining the zeolite octahedral metal oxides rather than the ϵ-Keggin polyoxometalate molecule. The synthesized zeolitic nickel molybdate with Na⁺ is used as the adsorbent, which effectively separates C₂ hydrocarbon mixtures.     

pH值对Bi_2MoO_6晶体形貌和可见光催化性能的影响

以(NH4)6Mo7O24·4H2O和Bi(NO3)3·5H2O为原料,采用普通水热法制备Bi2Mo O6光催化剂,研究p H值对制备该光催化剂的影响。对所制备的系列样品,采用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积分析仪、X射线光电子能谱仪(XPS)和紫外-可见漫反射(UV-Vis DRS)进行表征。结果表明:p H值对Bi2Mo O6晶体的物相组成、形貌和光催化性能均有显著影响。p H值为1~7时,所制备的样品为纯相Bi2Mo O6,p H值为9或11时,出现第二相Bi3.64Mo0.36O6.55;随着p H值的升高,形貌依次为纳米棒、纳米片和无规则纳米颗粒。在可见光(λ≥420 nm)照射下,通过光催化降解罗丹明B(Rhodamine B,Rh B),探讨了制备Bi2Mo O6的p H值对其可见光催化活性的影响。当p H=7时,制备的样品光催化效果最好,光照50 min后对初始浓度为5 mg·L-1的罗丹明B溶液的降解率为85%。     

Chemical composition and antioxidant activity of Borago officinalis L. leaf extract growing in Algeria

The aqueous and hydroalcoholic extracts of borage (Borago officinalis) leaves from Annaba region (Algeria) were preliminary analyzed for their phenolic profile (total phenolics, total flavonoids, total flavonols, total tannins and total anthocyanins). These extracts were evaluated for their antioxidant properties by different methods such as DPPH radical scavenging, test NBT and total antioxidant activity. The two extracts have exhibited a high antiradical capacity. Indeed, the ethanolic extract showed the lower IC50 values and the highest amount of phenolics (94.09 ± 1.72 mg gallic acid/g dry extract). Using LC-MS/MS analysis, it was possible to identify phenolic acids, flavonoids, sterol and for the first time oleuropein was identified in the aqueous extract of the plant. The obtained results have demonstrated that phenolic compounds are the major contributor to the antioxidant activity of plants.     

Co-precipitation synthesis,humidity sensing and photoluminescence properties of nanocrystalline Co2+ substituted zinc(II)molybdate (Zn1–xCoxMoO4; x = 0, 0.3, 0.5, 0.7, 1)

Zinc-cobalt molybdate composites (Zn_1–xCo_xMoO₄; x = 0, 0.3, 0.5, 0.7, 1) were synthesised by a simple co-precipitation method and characterised by thermogravimetric/differential thermal analysis (TG/DTA), Fourier transform-infrared (FT-IR), Fourier transform Raman (FT-Raman) spectroscopy, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM/EDAX) and transmission electron microscopy (TEM). The surface area was calculated by BET analysis in the adsorption/desorption isotherm. The humidity sensing properties of zinc-cobalt molybdates were tested by dc electrical measurements at different relative humidity environments (RH = 5–98%). The electrical resistance of the composites linearly decreases and the maximum sensitivity of 3672 ± 110 was observed for the Zn_0.3Co_0.7MoO₄ (ZnCM-4) composite towards humidity, which is calculated by the relation S_f = R_5%/R_98%, where the response time is 200 s and the recovery time is 100 s. Photoluminescence (PL) measurement at the room temperature of ZnM-1 composite exhibited a blue emission peak at 475 nm (λ_em) when excited at a wavelength (λ_ex) of 430 nm. During Co²⁺ substitution in Zn²⁺ matrix, a green and red emission peak was observed when excited at a wavelength (λ_ex) of 520 nm.     

Corrosion inhibition of ammonium molybdate for AA6061 alloy in NaCl solution and its synergistic effect with calcium gluconate

The corrosion inhibition of ammonium heltamolybdate (AH) and calcium gluconate (CG) for AA6061 alloy in 3% NaCl solution was investigated by the electrochemical measurements. It indicates that AH inhibits the corrosion of AA6061 alloy and acts as an anodic inhibitor. Maximum inhibition efficiency reaches 74.3% at the concentration of 1 × 10^?4 mol.l^?1 AH. The results of the electrochemical studies reveal AH is physically adsorbed on the AA6061 alloy surface and the adsorption follows Langmuir isotherm. The combination of AH and CG enhances the inhibition efficiency to 95.9%. The enhanced inhibition is attributed to the promotion of AH adsorption by CG. The mixture of AH and CG is a mixed‐type inhibitor and renders the corrosion potential to more positive values. Copyright © 2011 John Wiley & Sons, Ltd.     

Syntheses and Crystal Structures of Two Octamolybdate Compounds Modified by CuⅡ-Imidazole Cations

Two new polyoxomolybdate compounds,namely(CuIIL2)2[CuⅡ(HL)2]2[Mo8O26(HL)2].(H2O)4(1) and [CuⅡ(HL)2]2[β-Mo8O26](HL)2(2)(HL=imidazole),were designed and synthesized under hydrothermal conditions.X-ray diffraction analyses reveal that compound 1 consists of one Mo8O26(HL)24-cluster,two CuL2,two Cu(HL)22+,and four disassociated water molecules;and compound 2 is constructed by one β-Mo8O264-cluster,two Cu(HL)22+,and two uncoordinated imidazole molecules.     

A Two-dimensional Metallic Oxide Constructed from Molybdenum Clusters and Ag（Ⅰ）-[3-（2-pyridyl）-pyrazole] Cationic Coordination Components

A new polyoxomolybdate compound [Ag 3 (HL) 4 ](PMo 12 O 40)] 1 (HL=3-(2-pyridyl)pyrazole) has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,TG and IR spectroscopy.The compound crystallizes in triclinic,space group P1 with a=10.375(3),b=12.076(3),c=13.196(4),α=84.170(4),β=71.961(3),γ=86.326(4)°,V=1563.1(7)3,C 32 H 28 Ag 3 Mo 12 N 12 O 40 P,M r=2726.52,D c=2.897 g/cm 3,μ(MoKα)=3.366 mm 1,F(000)=1284,Z=1,the final R=0.0587 and wR=0.1312 for 4139 observed reflections (I > 2σ(Ⅰ)).X-ray diffraction analyses reveal that the PMo 12 O 40 3clusters in compound 1 are linked by four Ag 3 (HL) 4 3+ units via the terminal oxygen atoms to form a two-dimensional architecture.The symmetrical unit of Ag 3 (HL) 4 3+ exhibits two distinct Ag(Ⅰ) environments:a two-coordinate {AgN 2 } site and a five-coordinate {AgN 3 O 2 } site which links to two molybdate clusters.     

氧化石墨烯调控钼酸铋在可见光下选择性光催化降解环境水中的抗生素

以氧化石墨烯(GO)作为增强光催化剂活性的调节剂, 采用一步水热法制备钼酸铋/氧化石墨烯(Bi₂MoO₆/GO)异质结光催化剂, 其可见光响应拓展至570 nm, 带隙能降至2.56 eV. 当m_Bi2MoO6/m_GO=100∶1时, Bi₂MoO₆/GO(100∶1)光催化剂在可见光的辐射下, 对水溶液中四环素和喹诺酮类抗生素选择性的高效催化降解去除能力为Bi₂MoO₆的2.1倍. Bi₂MoO₆/GO(100∶1)光催化剂活性的提高依赖于范德华力作用下的二维Bi₂MoO₆纳米片-二维GO纳米片界面的紧密接触. 有效的界面接触改善了光生电子的转移和光生载流子的分离. 自由基清除实验结果表明, ?OH起主要作用. 结合高效液相色谱-质谱(HPLC-MS)法对降解产物的分析, 提出了不同光催化剂催化降解恩诺沙星具有相似的降解途径和降解产物.     

A2( MoO4)3(A=Al,Cr,Fe)结构与相变的Raman光谱研究

用XRD、Raman光谱和DSC研究了Al2 (MoO4)3、Cr2( MoO4)3和Fe2 (MoO4)3的结构与相变.Al2(MoO4)3、Cr2 (MoO4)3和Fe2 (MoO4)3在室温下为单斜相,分别在483 K、673 K和783 K附近转变为正交相.发现MO4四面体的对称和反对称伸缩振动模的频率和相对强...     

基于钨(钼)酸铋半导体复合材料的合成及其在光催化降解中的应用

由于全球的工农业的迅速发展,水污染已成为人类所面临的最大危机。基于半导体光催化法是治理水污染的绿色技术之一,能够有效地降解和去除水中的污染物。在众多光催化材料中,金属氧化物半导体由于其具有低毒性、高稳定性和对水溶液中化学腐蚀的较高的抵抗力等优点,而被科学家们广泛地研究和应用。其中,三元组分的金属氧化物因其具有较窄的禁带宽度和可见光响应性质,在光催化降解领域上的能力已经超过其他的金属化合物。本文系统地介绍了两种典型的三元金属氧化物——钨酸铋和钼酸铋,围绕着基于钨酸铋和钼酸铋的复合型催化剂的制备和在光催化降解废水处理领域中的应用以及发展进行了综述,提出了目前关于钨酸铋和钼酸铋的复合材料的设计、机理研究和改性修饰方法中的所存在的主要问题,并对未来的发展趋势进行了展望。